FAIZ UL ISLAM

Month: October 2024

  • 9th Class Physics Chapter 5: Gravitation

    9th Class Chapter 5: Gravitation Short and Simple Question & Answer

    On this page, you will find the Physics Estimate Paper for Class 9 for the year 2024, available in both English and Urdu. We offer two formats for downloading the most important questions for Class 9 Physics. This estimate paper is suitable for all boards in Punjab, including BISE boards in Faisalabad, Lahore, Gujranwala, Dera Ghazi Khan, Sargodha, Sahiwal, Multan, and Jammu Kashmir. Many students have successfully used the Physics Estimate Paper 2024 by Faiz Ul Islam to achieve good results in their exams.

    Q1.Define gravitation.

    Ans: In the universe, there exists a force between the bodies due to which everybody of the universe attracts every other body. This force is known as force of gravitation.

    Q2.State law of gravitation.

    Ans: Every object in the universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

    Q3.What is the relation between Law of Gravitation and Newton’s Third law of motion?

    Ans: It is to be noted that mass m1 attracts m2 towards it with a force F while mass m2 attracts m1 with a force of the same magnitude F but in opposite direction. If the force acting on m1 is considered as action then the force acting on m2 will be reaction. The action and reaction due to force of gravitation are equal in magnitude but opposite in direction. This is in consistence with Newton’s third law of motion which states, to every action there is always an equal but opposite reaction.

    Q4.What is Gravitational Field Strength?  

    Ans: In the gravitational field of the Earth, the gravitational force per unit mass is called gravitational field strength of the Earth. At any place its value is equal to the value of g at that point. Near the surface of the Earth, the gravitational field strength is 10 Nkg-1.

    Q5.Define orbital velocity.

    Ans: It is the velocity of the satellite with which it moves around the earth at specific height.

    Q6.What do you know about Global Positioning System.

    Ans: Global Positioning System (GPS) is a satellite navigation system. It helps us to find the exact position of an object anywhere on the land, on the sea or in the air. GPS consists of 24 Earth satellites. These satellites revolve around the Earth twice a day with a speed of 3.87 km s-1.

    Q7.What will happen if Earth suddenly stops revolving around the Sun?

    Ans: If Earth suddenly stops revolving around the Sun then due to attraction of sun and earth, it will fall down on the sun.

    Q8.What do you know about geostationary satellites?

    Ans: Geostationary satellites are the satellites whose velocity relative to earth is zero. These satellites remain stationary with respect to the earth at the height of 42,300 km from the surface of the earth. These are used for global TV transmissions and other telecommunication purposes.

    Q9.What is effect of the followings on the gravitational acceleration?

    • Mass of freely falling body
    • Distance of freely falling body from the centre of earth

    Ans: Effect of mass

    There is no effect of mass of the body on gravitational acceleration because according to the relation g = GM/R2. This relation shows that gravitational acceleration is independent of the mass of freely falling body.

    Effect of distance from the center of earth

    Gravitational acceleration is inversely proportional to the square of distance of freely falling body from the centre of earth. If the distance of the body is increased from the centre of the earth gravitational acceleration will be less and vice versa.

    Q10.Is there any difference between the value of ‘g’ at the equator and at the poles?

    Ans: As the shape of the earth is not perfect sphere but elliptical. The distance at the equator to the center of earth is more, so gravitational acceleration ‘g’ at equator will be less. However, as the distance at the poles to the center of the earth is less, so gravitation acceleration ‘g’ will be more.

    Q11.Moon revolves around the earth, from where it gets necessary centripetal force?

    Ans: The gravitational force between the earth and the moon provides the necessary centripetal force to moon for revolving around the earth.

    Q12.If we go on top of the mountain, will our weight increase or decrease?

    Ans: If the distance from the centre of the Earth increases from the average radius of the Earth, the value of ‘g’ will decrease. This is the reason due to which the value of ‘g’ is less on the top of mountains. So our weight will be decreased.

    Q13.Why do not we observe force of attraction between any two objects around us?

    Ans: Since the gravitational force between different objects around us is very small, so we do not feel it. However, if the mass of one or both the objects is very large, then we can observe the effect of gravitational force easily.

    Q14.What is the gravitational force acting on the body placed at the surface of Earth?

    Ans: Since the mass of the Earth is very large, it attracts nearby objects with a significant force. The weight of an object on the Earth is a result of the gravitational attraction between the two.

    Download PDf Format

    When preparing for their final exams, students can utilize the 9th-grade Physics assessment paper. Every chapter from the textbook is covered, along with questions that may appear on the exam. These essential questions serve as valuable study aids after students have completed the entire syllabus. By focusing on these key concepts, students can gauge their understanding and boost their confidence, ultimately enhancing their exam performance.

    Class 9 Physics Estimate Paper 2024 for Punjab Board Students

    Physics is often considered a challenging subject. The exam date for Class 9 Physics papers has been released, with all Punjab Boards conducting these papers on Friday. With limited time for preparation, using these important questions can significantly aid in covering the essential topics.

    Additionally, these questions will enhance your knowledge and help you prepare for the crucial questions expected in the exams. One of the standout features of our estimate paper is that it can be downloaded for free, allowing you to print these important questions at no cost.

  • 9th Class Physics Chapter 4: Turning Effect of Forces

    9th Class Chapter 4: Turning Effect of Forces Short and Simple Question & Answer

    On this page, you will find the Physics Estimate Paper for Class 9 for the year 2024, available in both English and Urdu. We offer two formats for downloading the most important questions for Class 9 Physics. This estimate paper is suitable for all boards in Punjab, including BISE boards in Faisalabad, Lahore, Gujranwala, Dera Ghazi Khan, Sargodha, Sahiwal, Multan, and Jammu Kashmir. Many students have successfully used the Physics Estimate Paper 2024 by Faiz Ul Islam to achieve good results in their exams.

    Q. What is meant by parallel forces?
    Ans:     In a plane, if number of forces act on a body such that their points of action are different but lines of action are parallel to each other, then these forces are called parallel forces. In the given figure, the forces F1, F2, F3 are acting at points A, B, C are parallel forces.

    Q.What is meant by like parallel forces? Also give examples.
    Ans:
    Like parallel forces are the forces that are parallel to each other and have the same direction.
    Examples:
    In the second figure, the direction of the parallel forces F1 and F3 is the same, so these are like parallel forces.

    Q.What are unlike parallel forces?
    Ans:     Unlike parallel forces are the forces that are parallel but have direction opposite to each other.
    Example:
    In the second figure, the parallel forces F1, F2 and F2, F3 are acting in opposite direction, so these are unlike parallel forces.

    Q.Define head to tail rule.
    Ans: Draw the representative lines of all the vector to be added in such a way that head of first vector coincides with the tail of second vector, head of second vector coincides with the tail of third vector and so on. The line obtained by joining the tail of first vector with the head of last vector represent resultant vector.

    Resultant Force
    A resultant force is a single force that has the same effect as the combined effect of the all the forces to be added. And resultant vector is drawn in such a way that tail of first vector is joined with the head of the last vector.

    Q.Define resolution of vectors.
    Ans:     The decomposition or division of a vector into its rectangular components is called resolution of a vector.

    OR

    The splitting of a single force into two mutually perpendicular components is called the resolution of that force.

    Q.Define torque or moment of force.
    Ans:     The rotational effect of a force is measured by a quantity, known as torque.

    Q.Define centre of mass.
    Ans:     Centre of mass of a system is such a point where an applied force causes the system to move without rotation.

    Q.Define centre of gravity.
    Ans:     A point in a body where the weight of the body appears to act vertically downward is called the centre of gravity.

    The centre of gravity can exist inside a body or outside the body. Position of the centre of gravity depends upon the shape of the body.

    Q.Define couple and give examples.
    Ans:     A couple is formed by two unlike parallel forces of the same magnitude but not along the same line.

    Examples:
    While turning a car, the forces applied on the steering wheel by hands provide the necessary couple.
    While opening or closing a water tap,
    While locking or opening the stopper of a bottle or a jar.

    Q.Define equilibrium.
    Ans:     A body is said to be in equilibrium if no net force acts on it.

    State conditions of equilibrium.

    First Condition of equilibrium:
    A body will be in equilibrium if the resultant of all the forces acting on it is zero. This is first condition of equilibrium.

    Second Condition of equilibrium:
    If a number of forces act on a body so that the total sum of the torques of these forces is zero, the body will be in equilibrium.

    Q.Define stable equilibrium.
    Ans:     A body is said to in stable equilibrium if after a slight tilt it returns to its previous position.

    When body is in stable equilibrium, its centre of gravity is at the lowest position. When it is tilted, its centre of gravity rises. It returns to its stable state by lowering its centre of gravity. A body remains in stable equilibrium as long as the centre of gravity acts through the base of the body.

    Examples:
    Table, chair, box and brick lying on a floor.

    Q.Define unstable equilibrium.
    Ans:     If a body does not return to its previous position when sets after a slightest tilt is said to in unstable equilibrium.

    The centre of gravity of the body is at its highest point in the state of unstable equilibrium. As the body topples over about its base, its centre of gravity moves towards its lower position and does not return to its previous position.

    Examples:
    A stick standing vertically on the tip of a finger.
    A cone standing on the tip of a finger.

    Q.Define neutral equilibrium.
    Ans:     Neutral equilibrium

    If a body remains in its new position when disturbed from its previous position, it is said to be in a state of neutral equilibrium. In neutral equilibrium the centre of gravity of body remains at the same height, irrespective to its new position.

    Example:

    A ball lying on the horizontal surface
    Motion of wheel on plane surface.

    Q.Define rigid body and axis of rotation.
    Ans:     Rigid body
    A body is composed of large number of particles. If the distance between all these pairs of particles of the body do not change by applying a force then it is called a rigid body.

    Axis of rotation
    During rotation, the particles of the rigid body move in circles with their centres all lying on a line. This straight line is called the axis of rotation of the body.

    Q.What is meant by principle of moments?
    Ans:     A body is balanced, if the sum of clockwise moments acting on the body is equal to the sum of anticlockwise moments acting on it.

    A body initially at rest does not rotate if sum of all the clockwise moments acting on it is balanced by the sum of all the anticlockwise moments acting on it. This is known as the principle of moments.

    Examples:
    A pencil, a sphere, and cylinder, a roller, an egg lying horizontally on a flat surface.

    Q.How stability of a body is related with the Position of centre of mass?
    Ans:     To make the body stable, their centre of mass must be kept as low as possible. It is due to the reason, racing cars are made heavy at the bottom and their height is kept to be minimum.

    Q.what factors rotation produce in a body depend?
    Ans:     Rotation produced in a body depends on the following two factors:

    Magnitude of the force.
    The perpendicular distance between the line of action of the force and the axis of rotation, that is known as moment arm.

    Q.How can we increase torque by keeping the force constant?
    Ans:     We can increase the torque by increasing the perpendicular distance from the line of action of force to the point of rotation that is moment arm by keeping the force constant, according to the relation τ = rF

    Q.Can a moving body be in equilibrium? Explain.
    Ans:     Yes, if a body is moving with uniform velocity then the body is in equilibrium because neither linear nor rotational acceleration is produced in the body.

    Q.Will a body be in equilibrium under the action of a single force?
    Ans:     No,the body will not be in equilibrium because first condition of the equilibrium will not be fulfilled. Since single force can never be zero and linear acceleration will be produced. Therefore we can say that a body cannot be equilibrium under the action of a single force.

    Q.Can a body be in equilibrium if it is revolving clockwise under the action of a single force?
    Ans:     No, the body will not be in equilibrium because second condition of the equilibrium will not be fulfilled. Since single torque can never be zero and rotational acceleration will be produced. Therefore we can say that a body cannot be equilibrium under the action of a single torque.

    Q.Give an example of a case when the resultant force is zero but resultant torque is not zero.
    Ans:     In case of couple, two equal and opposite forces are acting on a same body but even then the body rotates. In this case resultant force is zero but resultant torque is not zero.

    Example:
    While turning a car, the forces applied on the steering wheel by hands produce rotation in the steering wheel.

    Q.How do we know whether a body is in a stable or unstable equilibrium due to position of its centre of gravity?
    Ans:     If after disturbance, the centre of gravity of the body is raised up as compared to the initial position then the body will be in the state of stable equilibrium and if after disturbance, the centre of gravity of the body is lowered down as compared to the initial position then the body will be in the state of unstable equilibrium.

    Download PDF Format

    When preparing for their final exams, students can utilize the 9th-grade Physics assessment paper. Every chapter from the textbook is covered, along with questions that may appear on the exam. These essential questions serve as valuable study aids after students have completed the entire syllabus. By focusing on these key concepts, students can gauge their understanding and boost their confidence, ultimately enhancing their exam performance.

    Class 9 Physics Estimate Paper 2024 for Punjab Board Students

    Physics is often considered a challenging subject. The exam date for Class 9 Physics papers has been released, with all Punjab Boards conducting these papers on Friday. With limited time for preparation, using these important questions can significantly aid in covering the essential topics.

    Additionally, these questions will enhance your knowledge and help you prepare for the crucial questions expected in the exams. One of the standout features of our estimate paper is that it can be downloaded for free, allowing you to print these important questions at no cost.

  • 9th Class Physics Chapter 3: Dynamics

    9th Class Chapter 3: Dynamics Short and Simple Question & Answer

    On this page, you will find the Physics Estimate Paper for Class 9 for the year 2024, available in both English and Urdu. We offer two formats for downloading the most important questions for Class 9 Physics. This estimate paper is suitable for all boards in Punjab, including BISE boards in Faisalabad, Lahore, Gujranwala, Dera Ghazi Khan, Sargodha, Sahiwal, Multan, and Jammu Kashmir. Many students have successfully used the Physics Estimate Paper 2024 by Faiz Ul Islam to achieve good results in their exams.

    Q.1 Define­ dynamics.
    Ans:     The branch of mechanics that deals with the study of motion of an object and the cause of its motion is called dynamics.

    Q.Define force.
    Ans:     A force moves or tends to move, stops or tends to stop the motion of a body. The force can also change the direction of motion of a body.
    Example:
    We can open the door either by pushing or pulling the door.
    A man pushes the cart. The push may move the cart or change the direction of its motion or may stop the moving cart.
    A batsman changes the direction of moving ball by pushing it with his bat.

    Q.Define inertia. Explain it with examples.
    Ans:     Inertia of a body is its property due to which it resists any change in its state of rest or of uniform motion.
    It depends on the mass of the body. Greater the mass of the body greater will be the inertia. Therefore, we can say that mass is the direct measure of inertia.
    Example 1:
    Take a glass cover it with a piece of cardboard. Place a coin on the cardboard. Nowkick the card horizontally with a jerk of your finger. The coin does not move with the cardboard with the inertia and falls in to the glass.
    Example 2:
    Cut a strip of paper. Place it on the table. Stack a few coins at its on end. Pull out thepaper strip under the coins with a jerk. We will succeed in pulling out the paper strip under the stacked coin without letting them to fall due to inertia.

    Q.What is momentum?
    Ans:     Momentum of a body is the quantity of motion it possesses due to its mass and velocity.
    The momentum ‘P’ of a body is given by the product of its mass m and velocity v. Thus
    P = m x v
    Quantity
    Momentum is a vector quantity.
    Unit
    SI unit of momentum is kg ms-1 or Ns.

    Q.5 State Newton’s First law of motion.
    Ans:     A body continues in its state of rest or of uniform motion in a straight line provided no net force acts on it.

    Q.6 Why Newton’s First law of motion is also called law of inertia?
    Ans:     According to Newton’s first law of motion “A body continues its state of rest or of uniform motion in a straight line provided no net force acts on it”.
    The property of a body due to which it resists any change in its state of rest or motion is known as inertia.
    On comparing the above two statements we find that statement of Newton’s first law of motion is in accordance with statement of inertia. Therefore Newton’s first law of motion is known as law of inertia.

    Q.7 State Newton’s Second law of motion.
    Ans:     When a net force ‘F’ acts upon a body, it produces an acceleration in the body direction of force and the magnitude of acceleration is directly proportional to the force and is inversely proportional to the mass of the body.
    Mathematically F = ma

    Q.8 What is the unit of force? Define it.
    Ans: Unit of Force
    In the System International, the unit of force is newton, which is represented by the symbol ‘N’.
    Newton
    “One newton is that force which produces an acceleration of 1 ms-2 in a body of mass 1 kg”.
    This unit of force can also be written as,
    1 N = 1 kg x 1 ms-2
    1 N = 1 kgms-2

    Q.9 State Newton’s Third law of motion
    Ans:     To every Action there is always an equal but opposite reaction.
    So 1kgms-1 = R.H.S = 1 N s

    Ans: Rate of change of momentum of a body is equal to the applied force on it and the direction of change in momentum is in the direction of the force.

    Q.19 Suppose you are running and want to stop at once. Surely you will have to produce negative acceleration in your speed. Can you tell from where does the necessary force come?

    Q.20 Define circular motion.

    Ans: Motion of the body moving in the circular path is known as circular motion. Heavenly bodies have natural tendency to move in curved paths.

    Examples:

    The motion of the moon around the Earth is nearly in circular orbit.
    The paths of electrons moving around the nucleus in an atom are also nearly circular.
    Motion of the stone tied with the string

    Q.Define centripetal force.
    Ans:     A force that keeps a body to move in a circle is known as centripetal force.

    Or
    A force which compels the body to move in the circular path is known as centripetal force.

    Q. Define centripetal acceleration
    Ans:     The acceleration produced by the centripetal force which is always directed towards the center of the circle is known as centripetal acceleration. It is represented by ac.

    Q. Define and explain centrifugal force. Is it a reaction of centripetal force?

    Ans: Definition
    The force which compels a body to move away from circular path is known as centrifugal force. This is reaction of centripetal force.

    Example:
    Consider a stone tied with a string moving in a circle. The necessary centripetal force acts on the stone through the string that keeps it in the move in a circle. According to Newton’s third law of motion, there exists a reaction to centripetal force. Centripetal reaction that pulls the string outward is sometimes the centrifugal force.

    Q.Why outer edge of the road is kept higher than inner edge (banking of road)? Explain.
    Ans:     When a car takes a turn, centripetal force is needed to keep it in its curved track. The friction between the tyres and road provides the necessary centripetal force. The car would skid away if the force of friction between the tyres and the road is not sufficient enough particularly when the roads are wet. Banking of a road means that the outer edge of a road is raised. Banking causes a component of vehicle’s weight to provide the necessary force while taking a turn. Thus banking of road prevents skidding of vehicle and thus makes the driving safe.

    Q.Explain the function of washing machine (dryer).
    Ans:     The dryer of a washing machine is basket spinner. They have perforated wall having large numbers of fine holes in the cylindrical rotor. The lid of the cylindrical container is closed after putting wet clothes in it. When it spins at high speed, the water from wet clothes is forced out through these holes due to lack of centripetal force.

    Q.Explain the function of cream separator.
    Ans:     Most modern plants use a separator to control the fat contents of various products. A separator is a high – speed spinner. It acts on the same principle of centrifuge machine. The bowl spins at very high speed causing the heavier contents of the milk to move outwards in the bowl pushing the lighter contents inwards towards the spinning axis. Cream or butterfat is lighter than other components in the milk. Therefore, skimmed milk, which is denser than cream is collected at outer wall of the bowl. The lighter part (cream) is pushed towards the center from where it is collected through a pipe.

    Q.Why a cyclist bend himself toward the inner side of the curved path while taking turn with high speed?
    Ans:     A cyclist bend himself toward the inner side of the curved path while taking turn with high speed to provide necessary centripetal force with his weight to take turn in circular path to avoid slipping.

    Q.Can a body move with uniform velocity in a circle? If not, why?
    Ans:     When a body is moving in circle it may have uniform speed but its velocity is non-uniform because direction of the body is changing at every instant.

    Q.Can a body move along a circle without the centripetal force?
    Ans:     When a body moves in a circular path, it does so under the action of centripetal force. This force is directed towards the center along the radius of the circle. As the radius is perpendicular to the tangent of the circle, the centripetal force keeps the body in circular path. Thus, in absence of centripetal force, the body cannot move in a circular path.

    Q.Moon revolves around the earth, from where it gets necessary centripetal force?
    Ans:     The gravitational force between the earth and the moon provides the necessary centripetal force to moon for revolving around the earth.

    Download PDF Format

    When preparing for their final exams, students can utilize the 9th-grade Physics assessment paper. Every chapter from the textbook is covered, along with questions that may appear on the exam. These essential questions serve as valuable study aids after students have completed the entire syllabus. By focusing on these key concepts, students can gauge their understanding and boost their confidence, ultimately enhancing their exam performance.

    Class 9 Physics Estimate Paper 2024 for Punjab Board Students

    Physics is often considered a challenging subject. The exam date for Class 9 Physics papers has been released, with all Punjab Boards conducting these papers on Friday. With limited time for preparation, using these important questions can significantly aid in covering the essential topics.

    Additionally, these questions will enhance your knowledge and help you prepare for the crucial questions expected in the exams. One of the standout features of our estimate paper is that it can be downloaded for free, allowing you to print these important questions at no cost.

  • 9th Class Physics Chapter 2: Kinematics

    9th Class Chapter 2: Kinematics Short and Simple Question & Answer

    On this page, you will find the Physics Estimate Paper for Class 9 for the year 2024, available in both English and Urdu. We offer two formats for downloading the most important questions for Class 9 Physics. This estimate paper is suitable for all boards in Punjab, including BISE boards in Faisalabad, Lahore, Gujranwala, Dera Ghazi Khan, Sargodha, Sahiwal, Multan, and Jammu Kashmir. Many students have successfully used the Physics Estimate Paper 2024 by Faiz Ul Islam to achieve good results in their exams. Many students have successfully used the Physics Estimate Paper 2024 by Faiz Ul Islam to achieve good results in their exams.

    Q.1 Define Kinematics
    Ans:     The study of motion of an object without discussing the cause of motion is called the kinematics.

    Q.2 Define dynamics.

    Ans: The branch of mechanics that deals with the study of motion of an object and the cause of its motion is called dynamics.

    Q.3 How you will define the rest?

    Ans: If a body does not change its position with respect to its surroundings then it is said to be in a state of rest.

    Surrounding are the places in its neighborhood where various objects are present.

    Q.4 How you will define the motion?

    Ans: If a body continuously changes its position with respect to its surroundings then it is said to be in a state of motion.

    Q.5 How we can say that rest and motion are relative states?

    Ans: The state of rest or motion of a body is relative. For example, a passenger sitting in a moving bus is at rest because he/she is not changing his/her position with respect to the other passengers sitting in the bus. But to an observer outside the bus, the passengers and objects inside the bus are in motion because they are changing their positions.

    Q.6 Define Rotatory motion.

    Ans: The spinning motion of a body around its axis is called rotatory motion.

    Example:

    • Motion of Earth around its geographical axis
    • Motion of wheel and steering wheel around its axis
    • Motion of a ceiling electric fan
    • Axis of Rotation
    • A line around which a body rotates is called axis of rotation.

    Q.Differentiate between circular motion and rotatory motion
    Ans:

    Circular motion Rotatory motion
    1. The motion of an object in a circular path is known as circular motion.
    2. In circular motion the point about which a body goes around is outside the body.

    3. Examples:

    · Motion of earth around the sun.

    · Motion of moon around the earth.

    1. The spinning motion of a body about its axis is called rotatory motion.
    2. In rotatory motion the line around which a body moves about is passing through the body itself.

    3. Examples:

    · Motion of earth about its geographical axis.

    · Motion of a wheel about its axis.

    Q.8 Define Vibratory motion.

    Ans: To and fro motion of a body about its mean position is known as vibratory motion.

    Examples:

    • Motion of swing back and forth about its mean position
    • Motion of pendulum of wall clock
    • Motion of see – saw
    • Motion of a body attached with a spring.

    Q.9 What do you know about scalar and vector quantities (LHR 2014, 2015)

    Ans: A physical quantity which can be completely described by its magnitude only is called a scalar. The magnitude of a quantity means its numerical value with an appropriate unit.

    Examples:

    Mass, length, time speed, volume, area, energy etc.

    Vector

    physical quantity which can be completely described by its magnitude along with its direction.

    Example:

    Velocity, force, displacement, momentum, torque etc.

    Q.10 How a vector is represented?

    Ans: Symbolical Representation

    A vector is represented symbolically by a letter (an alphabet) with an arrow drawn above or below the symbol as . A vector quantity can also be represented symbolically by using bold letters such as A.

    Graphical Representation

    Graphically, a vector can be represented by a line segment with an arrow head at its one end. The length of line, according to some selected scale, gives the magnitude of the vector and an arrow head at one end of the line gives the direction of the vector. The line AB drawn according to some selected scale with an arrow head represents the vector graphically.

    Q.11 What is Position?

    Ans: The term position describes the location of place or a point with respect to some reference point called origin.

    Example:
    Suppose you want to describe the position of your school from your home. Let the school be represented by S and home by H. The position of your school from your home will be represented by a straight line HS in the direction from H to S as shown in Fig.

    Q.12 What is meant by distance?

    Ans: Distance

    The total length/separation of a path between two points is known as distance between those points.

    Quantity

    It is a scalar quantity

    Unit

    Its SI unit is meter (m).

    Representation

    It is represented by “S”.

    Q.13 What do you know about Displacement?

    Ans: The shortest distance between two points is known as displacement which has magnitude and direction.

    Representation

    It is represented by “ ”.

    Quantity

    It is a vector quantity and it is directed from initial to final point.

    Unit

    Its SI unit is meter (m).

    Q.14 What do you know about speed?

    Ans: The distance covered by an object in unit time is known as its speed.

    Mathematical form

    If a body covers distance ‘S’ in time ‘t’ then its speed ‘v’ can be mathematically written as,

    Speed = Distance covered/Total time

    v = D × t

    Distance = speed x time

    S = v × t

    Quantity

    It is a scalar quantity.

    Unit

    SI unit of speed is meter per second (ms-1).

    Q.15 How you will define the uniform speed?

    Ans: If a body covers equal distances in equal intervals of time, however small the intervals may be, the speed of the body is said to be uniform.

    Q.16 Define variable speed.

    Ans: A body has variable speed if it covers unequal distances in equal intervals of time however short the interval may be.

    Q.17 A body is moving with uniform speed. Will its velocity be uniform?

    Ans: A body moving with uniform speed may have uniform or variable velocity.

    If the direction of the body is not changing then its velocity will also be uniform.

    Example 1

    A car moving with uniform speed in the straight line will have uniform velocity.

    If the direction of the body is changing then its velocity will be variable.

    Example 2

    A car moving with uniform speed in the circular path will have variable velocity because its direction changes at every point on the circle.

    Q.18 What do you know about velocity?

    Ans: The rate of displacement of a body is called velocity.

    Mathematical form

    Here is the displacement of the body moving with velocity in time t.

    Quantity

    It is a vector quantity and its direction is same as the direction of displacement.

    Unit

    SI unit of velocity is same as that of speed that is meter per second (ms-1).

    Q.19 What do you know about uniform velocity?

    Ans: A body has uniform velocity if it covers equal displacement in equal intervals of time however short the interval may be.

    Q.20 Define variable velocity.

    Ans: A body has variable velocity if it covers unequal displacement in equal intervals of timehowever short the interval may be.

    Q.21 Does speedometer of a car measure its velocity?

    Ans: The speedometer of a car measures only magnitude of velocity not the direction. Therefore, we can say that speedometer of the car does not measure its velocity. It measures only speed.

    Q.22 Why a body moving along a circle with uniform speed has variable velocity?

    Ans: A body moving along a circle with uniform speed has variable velocity because its direction is changing at every point on the circular path.

    Q.23 What is meant by the acceleration?

    Ans: The rate of change of velocity of a body is known as acceleration.

    Mathematical form

    If a body is moving with initial velocity ’vi’ and after some time ‘t’ its velocity becomes ‘vf’ then change in velocity will be vf–vi in time t.

    Unit

    SI unit of acceleration is meter per second per second (ms-2).

    Quantity

    It is a vector quantity.

    Q. What is meant by uniform acceleration?
    Ans:     If a body has equal changes in velocity in equal intervals of time, however small the intervals may be, then the acceleration of the body is said to be uniform.

    Q.25 Define variable acceleration.

    Ans: A body has variable acceleration if it has unequal changes in velocity in equal intervals of time however short the interval may be.

    Q.26 What is meant by positive acceleration and negative acceleration?

    Ans: Positive acceleration
    If the velocity of the body is increasing then acceleration will be positive. The direction of positive acceleration is the same in which the body is moving without change in its direction.

    Example:

    If a car is moving in straight line and the driver presses the accelerator the velocity of the car starts to increase. So the acceleration of the body will be positive.

    Negative acceleration or retardation
    If the velocity of the body is decreasing then acceleration will be negative. The direction of negative acceleration is opposite to the direction in which the body is moving. Negative acceleration is also called retardation or deceleration.

    Example:
    If the driver applies brake, the velocity will start to decrease. So acceleration of the body will be negative and direction of acceleration is opposite to the direction of velocity.

    Q. A body moving with uniform velocity. What will be its acceleration?

    Ans: A body is moving with uniform velocity then its acceleration will be zero because acceleration is defined as the rate of change of velocity. When the body is moving with uniform velocity, the change in velocity will be zero and therefore the acceleration will also be zero.

    Q. Can a body moving with certain velocity in the direction of east can have acceleration in the direction of west?
    Ans:     Yes, a body moving with certain velocity in the direction of east can have acceleration in the direction of west. It is the case when the velocity of the body decreases. When velocity decreases, acceleration is produced in opposite direction to the direction of motion.

    Q. What do you know about graph?
    Ans:     Graph is a pictorial way of presenting the information about the relation between various quantities. The quantities used in plotting a graph are called the variables.

    Q. Independent variable quantity

    Ans: The quantity which can be changed with our wish is called independent variable quantity.

    Q. Dependent variable quantity

    Ans: The quantity, value of which varies with the change in independent variable quantity is called the dependent variable quantity.

    Q. What do you know about gravitational acceleration?
    Ans:     If we neglect air resistance, then all the bodies either lighter or heavier will fall down with uniform acceleration. This uniform acceleration of freely falling bodies is known as gravitational acceleration. It is represented by ‘g’. Its value is 9.8ms-2, but for simplicity we shall use the value of g as 10ms-2. For bodies falling vertically downward ‘g’ is positive and for bodies moving vertically upward ‘g’ is negative.

    Q. How can we use equations of motion for bodies, which are falling freely under the gravity?
    Ans: Equations of motion can be used for bodies moving under gravity. In such cases we replace ‘a’ by ‘g’ and S by h. so equations of motion for bodies falling freely can be written as,

    vf = vi + gt

    h = vit + gt2

    2gh = vf2 – vi2

    Q. What are the points kept in mind when bodies are moving freely under gravity?
    Ans:     When bodies are moving in downward direction:

    Initial velocity ‘vi’ of the freely falling body will be zero
    Gravitational acceleration will be positive
    When bodies are moving in upward direction:

    Final velocity ‘vf’ of the body will be zero.
    Gravitational acceleration will be negative.

    Q. When a body is thrown vertically upward, its velocity at the highest point is zero. Why?
    Ans:     When a body is thrown vertically upward, it moves against the force of attraction of the earth. It slows down gradually and on reaching the highest point it comes to rest. That is why the velocity of a body becomes zero at the highest point.

    Download PDF Format

    When preparing for their final exams, students can utilize the 9th-grade Physics assessment paper. Every chapter from the textbook is covered, along with questions that may appear on the exam. These essential questions serve as valuable study aids after students have completed the entire syllabus. By focusing on these key concepts, students can gauge their understanding and boost their confidence, ultimately enhancing their exam performance.

    Class 9 Physics Estimate Paper 2024 for Punjab Board Students

    Physics is often considered a challenging subject. The exam date for Class 9 Physics papers has been released, with all Punjab Boards conducting these papers on Friday. With limited time for preparation, using these important questions can significantly aid in covering the essential topics.

    Additionally, these questions will enhance your knowledge and help you prepare for the crucial questions expected in the exams. One of the standout features of our estimate paper is that it can be downloaded for free, allowing you to print these important questions at no cost.

  • 9th Class Physics Chapter 1: Physical Quantities and Measurement

    9th Class Chapter 1: Physical Quantities and Measurement Short and Simple Question & Answer

    On this page, you will find the Physics Estimate Paper for Class 9 for the year 2024, available in both English and Urdu. We offer two formats for downloading the most important questions for Class 9 Physics. This estimate paper is suitable for all boards in Punjab, including BISE boards in Faisalabad, Lahore, Gujranwala, Dera Ghazi Khan, Sargodha, Sahiwal, Multan, and Jammu Kashmir. Many students have successfully used the Physics Estimate Paper 2024 by Faiz Ul Islam to achieve good results in their exams.

    Q.1 What is Science?
    Ans:     The knowledge gained through observations and experimentations is called science. The word science is derived from the Latin work scientia which mean knowledge.

    Q.2 What Physics?
    Ans:     Physics is that branch of science in which we study matter, energy and their interaction. The laws and principles of physics help us to understand nature.

    Q.3 What are the physical quantities?
    Ans:     All measurable quantities are called physical quantities. These are characteristics of every object which are used to be measured to specify them. These characteristics of the object are known as physical quantities.
    Example:
    Length, time, mass, force, speed, volume, volume, density etc.

    Q.4 What are the basic characteristics of physical quantities?
    Ans:     A physical quantity possesses at least two characteristics in common.
    (i) Numerical magnitude
    (ii) Unit in which it is measured.

    Q.5 What are the base quantities?
    Ans:     The physical quantities which form the foundation for other physical quantities are called base quantities. Base quantities are the quantities on the basis of which other quantities are expressed.
    Example: These are length, time, mass, electric current, intensity of light, quantity of matter, and temperature. These are seven quantities in total.

    Q.6 What are the derive quantities?
    Ans:     All the quantities, which can be described in terms of base quantities, are known as derived quantities. The quantities that are expressed in term of base quantities are called derived quantities.
    Example: Force, area, volume, density etc.

    Q.7 Why a standard unit is needed to measure a quantity correctly?
    Ans:     To measure a quantity, we need to compare it with some standard quantity. While measuring the physical quantity, we have to see that how many times this quantity is bigger or smaller than the standard quantity. Therefore stand unit is needed to measure a quantity correctly.

    Q.8 What do you know about International System of Units (SI)?
    Ans:     With the development in the field of science and technology, the need for commonly acceptable system of units was seriously felt all over the world particularly to exchange scientific and technical information. The eleventh General Conference on weight and Measures held in Paris in 1960 adopted a worldwide system of measurements called International system of units. The International system of units referred as SI.

    Q.9 What are the base units?

    Ans: The units that describe the base quantities are called base units. Each base quantity has its SI unit. There are seven base units. The following table shows the base quantities and its units.

    Q.10 What are derived units?

    Ans: The units used to measure derived quantities, which are derived from base units, are called derived units.

    • Example:
    • Unit of speed is meter per second (ms¹).
    • Unit of force is Newton (N).
    • Unit of volume is meter cube (m³)
    • Unit of charge is coulomb (C)

    Q.11 How numbers are expressed in Scientific Notation?
    Ans:     Very small or very large numbers are expressed conveniently by using the scientific method based as some power of ten multiplied by a number between 1 and 10.
    OR A simple but scientific way to write large or small numbers is to express in some power of
    ten.

    Q.12 What do you know about Meter Rule?
    Ans:     It is an instrument which is used in laboratories to measure the length of an object or distance between two points.
    Scale
    It is one meter long which is equal to 100 centimeters. Each centimeter is divided into 10 small divisions called millimeter (mm).
    Least count
    The least count of meter rule is 1mm. This is the minimum length that can be accurately measured by the meter rule.
    Precautions
    While measuring the length, or distance with the help of meter rule, we should kept the eye vertically above the reading point. The reading becomes doubtful if the eye is positioned either left or right to the reading point.

    Q.13 Explain the statement, “A micrometer screw gauge measures more accurately than a vernier calipers”.

    Ans: A micrometer screw gauge can measure more accurately than a vernier calliper because a micrometer screw gauge can accurately measure up to one hundredth part of a millimeter whereas vernier calipers can only measure accurately up to one tenth part of a millimeter.

    Q.14 What do you know about Lever balance?
    Ans:     A lever balance consists of a system of levers. When lever is lifted placing an object in one pan and standard masses on the other pan, the pointer of the lever system move. The pointer is brought to zero by varying standard masses.

    Q.15 What is electronic balance? What is its range? And how mass is measured by using electronic balance?
    Ans:     It is an instrument used to measure the mass of the body electronically.
    Range
    Electronic balance comes in various ranges; milligram ranges, gram ranges and kilogram ranges.
    Procedure to measure mass
    Before measuring the mass of the body, it is switched on, and its reading is set to zero.
    Next place the object to be weighted.
    The reading on the balance gives you the mass of the body placed over it.

    Q.16 What do you know about Measuring Tape?
    Ans:     Measuring tapes are used to measure length in meters and centimeters. Measuring tapes are used by blacksmith and carpenters.
    Formation:
    A measuring tape consists of a thin long strip of cotton, metal or plastic. It can measure generally 10 m, 20 m, 50 m, 100 m. Measuring tapes are marked in centimeters as well as in inches.

    Download PDF Format

    When preparing for their final exams, students can utilize the 9th-grade Physics assessment paper. Every chapter from the textbook is covered, along with questions that may appear on the exam. These essential questions serve as valuable study aids after students have completed the entire syllabus. By focusing on these key concepts, students can gauge their understanding and boost their confidence, ultimately enhancing their exam performance.

    Class 9 Physics Estimate Paper 2024 for Punjab Board Students

    Physics is often considered a challenging subject. The exam date for Class 9 Physics papers has been released, with all Punjab Boards conducting these papers on Friday. With limited time for preparation, using these important questions can significantly aid in covering the essential topics.

    Additionally, these questions will enhance your knowledge and help you prepare for the crucial questions expected in the exams. One of the standout features of our estimate paper is that it can be downloaded for free, allowing you to print these important questions at no cost.

  • 9th Class Chemistry Chapter 8: Chemical Reactivity

    9th Class Chapter 8: Chemical Reactivity Short and Simple Question & Answer

    We know you are looking for 9th class Chemistry Chapter 8 English medium notes according to the new syllabus for 2020. That’s why we have uploaded comprehensive, easy-to-understand, and precise notes for 9th class Chemistry tailored for the Punjab board session 2020-2021. You can download these notes or view them online. Many students practice 2024 Biology important questions by FAIZ UL ISLAM and get good marks in the exam.

    Q1: Define metal. How metals, can be categorized?

    Ans: Metals are the elements which are electropositive and form cations by losing electrons. Metals can be categorized in followings: a. Very reactive metals b. Moderately metals c. Least reactive metals

    Q2: Write down any two physical properties of metals.

    Ans: Physical properties of metals are: a. Almost all metals are solids. b. All metals have high melting and boiling points.

    Q3: Write down any two chemical properties of metals.

    Ans: Chemical properties of metals are: a. Metals can easily lose electrons and form positive ions b. Metals readily react with oxygen to form basic oxides.

    Q4: Define electropositive character.

    Ans: Metals have the tendency to lose their valence electrons. This property of a metal is called electropositive character or metallic character e.g. NaNa++ le

    Q5: Write down the trends of electropositive character in periodic table.

    Ans: Electropositive character increases down the group and decreases from left to right in a period.

    Q6: Why the 2nd ionization energy of magnesium is very high than the first one?

    Ans: The 2nd ionization energy of magnesium is very high because, it is difficult to remove second electron from the Mg ion as nuclear charge attracts the remaining electrons strongly. As a result of nuclear attraction size of the ion decreases. So, it is difficult to remove 2+ electron from magnesium ion.

    Q7: What type of elements are metals?

    Ans: The elements which are electropositive and form cation by losing electrons. This type of elements are metals.

    Q8: Name the metal which exists in liquid form.

    Ans: Mercury exists in liquid state at room temperature.

    Q9: What is the nature of metallic oxides?

    Ans: The metallic oxides are basic in nature because they change red litmus paper to blue.

    Q10: Which group of metals is highly reactive?

    Ans: Group-1 of the periodic table is highly reactive in nature.

    Q 11: Sodium metal is more reactive than magnesium. Why?

    Ans: Because sodium is oxidized easily and has low ionization energy whereas magnesium is not easily oxidized and has high ionization energy that is why sodium is more reactive.

    Q12: Name the metal which can be cut with knife?

    Ans: Sodium metal can be cut with knife.

    Q13: Name the best ductile and malleable metal.

    Ans: Cesium is the best ductile and malleable metal.

    Q14: Name the metal which is the poorest Conductor of heat?

    Ans: Lead metal is the poorest conductor of heat.

    Q15: What do you mean by malleable and ductile?

    Ans: Malleable means can be hammered into sheets and ductile means can be drawn into wires.

    Q16: What do you mean by metallic character?

    Ans: Metals have the tendency to lose their valence electrons. This property of metal is termed as metallic character.

    Q17: Why metallic character increases in group and decreases in a period?

    Ans: Metallic character increases in group and decreases in a period because top to bottom in a group atomic size increases and left to right in a period atomic size decrease.

    Q18: Define transition elements.

    Ans: The elements in which d-orbital’s are in the process of filling, constitute a group of metals called transition metals.

    Q19: Give the application of silver.

    Ans: Silver has important-applications in mirror industry.

    Q20: Why sliver is not used in pure form?

    Ans: Because, the formation of oxide or sulphide layer on the surface of silver, makes it relatively inactive in nature, therefore, silver is not used in pure form.

    Q21: What do you mean by 24 carat of Gold?

    Ans: Purity of gold is shown by carats. That indicates the number of parts by weight a gold that is present is 24 parts of alloy. 24 carrot gold is pure in nature.

    Q22: Why gold is used to make jewelry?

    Ans: Because of its inertness in atmosphere, it is an ornamental Metal so it is used to make jewelry.

    Q23: Why platinum is used for making jewelry?

    Ans: Platinum is used to make jewelry items because of its unique strength, flexibility and resistance to tarnish.

    Q24: Write down the difference between steel and stainless steel.

    Ans: Difference between steel and stainless steel is: Steel: Pure steels is the alloy of iron with other metals like nickel, tungsten Stainless steel: Stainless steel is the alloy of iron with chromium

    Q25: How platinum is used as a catalyst in automobile and what we advantage of this use?

    Ans: Platinum alloyed with palladium and rhodium is used as catalyst in automobiles as catalytic converter. They convert most of the gases being emitted by vehicles into less harmful carbon dioxide, nitrogen and water vapors.

    Q26: What are non-metals?

    Ans: Non-metals form negative ions (anions) by gaining electronegative in nature and form acidic oxides. electrons In this way non-metals are

    Q27: On what factor non-metallic character depends?

    Ans: The non-metallic character depends upon the electron affinity and electronegativity of the atom.

    Q28: Write down the non-metallic character r in periodic table.

    Ans: Non-metallic character decreases from top to bottom in any group and increases left to right in a period.

    Q29: Write down two physical properties of non-metals.

    Ans: Physical properties of non-metals are: a. Non-metals are non-conductor of heat and electricity. b. Non-metals have low melting and boiling points.

    Q30: Write down two chemical properties of non-metals.

    Ans: Chemical properties of non-metals are: a. Non-metals form ionic compounds with metals and covalent compounds by reacting with one another e.g. CO2, NO2 etc. b. Non-metals usually do not react with water.

    Q31: What are halogens?

    Ans: Halogen means salt former. Elements of group-7 of the periodic table consist of fluorine, chlorine, bromine iodine and astatine. They are collectively called halogens.

    Q32: Write down the physical properties of halogens.

    Ans: Both fluorine and chlorine exist in gases form, bromine exists in liquid form and iodine exists in solid form.

    Q33: Why valency of chlorine is 1?

    Ans: Valency of chorine atom is 1 because it accepts only | electron in its outermost shell.

    Q34: Which factor controls the non-metallic character of the elements?

    Ans: The non-metallic character depends upon the electron affinity and electronegativity of the atom.

    Q35: Why fluorine is more non-metallic than chlorine?

    Ans: Because non-metallic character decreases in a group downward and increases in a period from left to right. Fluorine is the first member of group 17 and non-metallic character decreases down the group that is why fluorine is more non-metallic than chlorine.

    Q36: Iodine exists in solid state; can it be beaten with hammer to form sheets?

    Ans: No, only solid substances or metals that have the ability to change in sheets by beaten with hammer.

    Q37: Can liquids and gases be brittle?

    Ans: No, because it is not the property of liquids and gases.

    Q38: Why the oxygen is called non-metal?

    Ans: Oxygen is non-metal because all non-metals form negative ions by negative ios gaining electrons.

    Q39: Name two non-metals which are both brittle and non-ductile.

    Ans: Silicon and graphite are two non-metals which are brittle and non-ductile.

    Q40: Name the most abundant non-metal in the earth crust.

    Ans: Oxygen has the highest percentage in earth s crust i.e. 47% and in ocean 86%

    Q41: Give the non-metallic trend of halogens.

    Ans: Non-metallic character decreases from top to bottom in halogens because of increasing atomic size of atoms.

    Q42: Why do the non-metals accept electrons readily?

    Ans: The non-metals accept electrons readily because non-metals are electronegative in Nature and electron deficient in nature so they form an anion by gaining electrons.

    Q43: Why non-metals do not react with dilute acid while metals do react with acid?

    Ans: The non-metals do not react with dilute acids because non-metals are itself electron acceptor and metals loss electrons readily.

    Q44: How we can distinguish a substance is metal or non-metals with the help of an acid?

    Ans: Yes, we can distinguish a substance is metal or non-metal with the help of an acid as: Metals: Metals react with dilute acids because metals are itself electron donors. Non-Metals: Non-metals do not react with dilute acids because non-metals are itself electron acceptors.

    Q45: Why is HF weak acid?

    Ans: Because HF does not release its proton easily due to presence of hydrogen bonding.

    Q46: Write down the names of very reactive metals.

    Ans: Potassium, sodium, calcium, magnesium and aluminum are the very reactive metals.

    Q47: Write down the names of moderately reactive metals.

    Ans: Zinc, Iron, Tin and Lead are the moderately reactive metals.

    Q48: Write down the names of least Reactive or Noble metals.

    Ans: Copper, mercury, silver and gold are the least reactive metals.

    Q49: Why reactivity of metals increase down the group?

    Ans: The reactivity of metals increases down the group because of increasing atomic size.

    Q50: State the physical properties of metals.

    Ans: The Physical properties of metals are as: a. Metals have high melting and boiling point b. Metals are good conductor of heat and electricity

    Q51: Why nitrogen forms compounds with alkaline earth metals directly?

    Ans: Because alkaline earth metals form stable nitride when heated with nitrogen directly.

    Q52: Why the second ionization energy of magnesium is higher than the first one?

    Ans: It becomes very difficult to remove second electron from the magnesium ion Mg+¹ because nuclear charge attracts the remaining electrons strongly as the result of this attraction size of the ion decreases.

    Q53: How oxygen reacts with group II metals?

    Ans:Alkaline earth metals are less reactive towards oxygen. They form oxides when heated with oxygen. 2Mg+O2→ 2MgO

    Q54: What is the relationship between electro positivity and ionization energy?

    Ans: Electro positivity depends upon the ionization energy which in turn depends upon size and nuclear charge of the atoms. So smaller sized atoms with high nuclear charge have high ionization energy. Atoms having high ionization energy are less electro positive or metallic.

    Q55: Why electro positivity decreases from left to right in a period?

    Ans: Because electropositive character depends upon the size of the atom. Electropositive character decreases across the period due to decrease in atomic size.

    Q56: How electro positivity depends upon the size and nuclear charge of an atom?

    Ans: Electropositive character depends upon the size of the atom, greater the size of the atom, greater will be the electropositive character and less nuclear charge. Smaller the size of the atom, smaller will be the electropositive character and greater nuclear charge

    Q57: Why ionization energies of alkaline earth metals are higher than alkali metals?

    Ans: Ionization energy of alkaline earth metals is high than alkali metals because the atomic size of alkaline earth metals are smaller and greater nuclear charge.

    Q58: Why silver and gold are less reactive?

    Ans: Silver and gold are less reactive because gold and silver are relatively inactive metals and they do re relatively not loss electron easily that’ t’s why gold and silver are less reactive.

    Q59: Can pure gold be used for making ornaments? If not why?

    Ans: No, pure gold cannot be used for making ornaments because gold is too soft and it always used in alloy form with copper, silver ror some other metals.

    Q60: Why copper is used for making electrical wire?

    Ans: Because it is good conductor of heat and electricity.

    Q61: What is the trend of variation of in densities of alkali metals?

    Ans: Densities of alkali metals increase down the group in the periodic table due to increase in atomic mass.

    Q62: Which metal is used for metal work?

    Ans: Metal work means fire work. The metals are used for the metal works or fire work due to its characteristics flame colour when they ignite in air for example sodium gives golden yellow colour and calcium gives red colour flame.

    Q63: Why magnesium is harder than sodium?

    Ans: Magnesium is harder than sodium because magnesium has high ionization energy and stronger metallic bond than sodium,

    Q64: Why calcium is more electropositive than magnesium?

    Ans: Calcium and magnesium are belonged to the same group and electro positivity of metals increases when we move from top to bottom in a group that is why calcium is more electropositive than magnesium.

    Q65: Why ionization energy of sodium is less than magnesium?

    Ans: Because sodium has greater size than magnesium that is why the ionization of sodium is less than magnesium.

    Q66: Why the ionization energy of sodium is more than potassium?

    Ans: Because electro positive character depends upon the ionization energy which in turn depends on size and nuclear charge of the atom. So the electro positive character increases down the group and ionization value decreases, it become easier to lose their electrons. That why ionization energy of sodium is more than potassium.

    Q67: Write down the uses of Sodium.

    Ans: Uses of Sodium are as: a. Sodium-potassium alloy is used as a coolant in nuclear reactor. b. It is used to produce yellow light in sodium vapour lamp. c. It is used as a reducing agent in the extraction of metals like Ti.

    Q68: Write down the uses of Calcium.

    Ans: Uses of Calcium as: a. It is used to remove Sulphur from petroleum products, b. It is used as reducing agent to produce Cr, U, Zr.

    Q69: Write down the uses of Magnesium.

    Ans: Uses of Magnesium are as: a. Magnesium is used in flash lights and in fireworks. in firew b. It is used in the manufacture of light alloys. c. Magnesium ribbon is used in Thermite process to ignite aluminum powder. d. Magnesium is used as anode for prevention of corrosion.

    Download PDF Format

    The 9th class Punjab Textbook of Chemistry is an excellent starting point for your scientific journey. Besides this book, it’s beneficial to gather additional information from various online resources. This post provides you with the 9th Class Notes for Chemistry, including multiple posts for each chapter. Each chapter post contains a variety of questions, including Short Questions, Long Questions, and Multiple-Choice Questions.

    Be sure to like our Facebook page for educational updates from Faiz ul Islam.

    These 9th class notes are prepared according to the syllabus of all Punjab Boards, including Gujranwala Board, Lahore Board, Faisalabad Board, Multan Board, Rawalpindi Board, Bahawalpur Board, Sargodha Board, DG Khan Board, and Sahiwal Board.

  • 9th Class Chemistry Chapter 7: Electrochemistry

    9th Class Chapter 7: Electrochemistry Short and Simple Question & Answer

    We know you are looking for 9th class Chemistry Chapter 7 English medium notes according to the new syllabus for 2020. That’s why we have uploaded comprehensive, easy-to-understand, and precise notes for 9th class Chemistry tailored for the Punjab board session 2020-2021. You can download these notes or view them online. Many students practice 2024 Biology important questions by FAIZ UL ISLAM and get good marks in the exam.

    Q1: What is meant by electrochemistry?

    Ans: The branch of chemistry that deals with the relationship between electricity and chemical reactions is called electrochemistry.

    Q2: Define oxidation.

    Ans: Oxidation is defined as the addition of Oxygen or Removal of Hydrogen or loss of Electron or increase in oxidation number during a chemical reaction. C+O2→ CO₂

    Q3: Define reduction.

    Ans: Reduction is defined as the removal of oxygen 1 or addition of hydrogen or gain of electrons decrease in oxidation number during a chemical reaction. CuO+H₂Cu+H₂O

    Q4: What is meant by Redox?

    Ans: Chemical reactions in which the oxidation state of one or more substances changes are called oxidation-reduction or Redox reactions, H₂S+Cl2→ 2HC1+S

    Q5: What is meant by oxidizing agent? Give examples. Ans: An oxidizing agent is a species that oxidizes a substance by taking electrons from it. The substance (atom or ion) which is reduced itself by gaining electrons is called oxidizing agent. For example a) Concentrated Sulphuric acid H2SO4 b) Potassium permanganate. KMnQ4

    Q6: What is meant by reducing agent? Give examples.

    Ans: Reducing agent is the species that reduces a substance by donating electron to it. The substance (atom or ion) which is oxidized by losing electrons is called reducing agent. For example a) Hydrogen (H) b) Hydrogen sulphide (H2S)

    Q7: What are spontaneous reactions?

    Ans: Spontaneous reactions are those which take place on their own without any external agent.

    Q8: What are non-Spontaneous reactions?

    Ans: Non-spontaneous reactions are those which take place in the presence of external agent.

    Q9: What is meant by Oxidation State?

    Ans: Oxidation state or oxidation number is the apparent charge assigned to an atom of an element in a molecule or in an ion. For example in HCl, the oxidation number of hydrogen is +1 and

    Q10: Define valency.

    Ans: The apparent charge on an atom, ion or molecule is called valency. It is written as their sign. followed by the number i.e., 2+ OR The combining power of an atom to another atom is called its valency

    Q11: What is meant by electrochemical cell?

    Ans: Electrochemical cell is a system in which two electrodes are dipped in the solution Of an electrolyte which is connected to the Battery. OR Electrochemical cell is an energy storage device in which either a chemical reaction takes place by using electric current or chemical reaction produces electric current.

    Q12: What are electrolytes?

    Ans: The substances, which can conduct electricity ity in the in their solutions or molten states, are called electrolytes. For example, solutions of salts, acids or bases are good electrolytes.

    Q13: What are strong electrolytes?

    Ans: The electrolytes which ionize completely i in aqueous solution and produces more ions, are called strong electrolytes. For example, NaCl, NaOH, H_{2}*S*O_{4} are strong electrolytes.

    Q14: What are weak electrolytes?

    Ans: The electrolytes which ionize to a small extent when dissolved in water and could not produce more ions are called weak electrolytes. For example, C*H_{3}*COOH Ca (OH) 2 etc.

    Q15: What are non-Electrolytes?

    Ans: The substances, which do not ionize in solution and do not allow the current to pass through their solutions, are called non-electrolytes. For example, sugar solution, benzene etc.

    Q16: What is meant by electrolytic cell?

    Ans: The type of electrochemical cell in which a non-spontaneous chemical reaction takes place when electric current is passed through the solution, is called an electrolytic cell c.g. Down’s cell.

    Q17: Define Cation.

    Ans: Chemical specie which carries a positive charge. e.g., N a^ + . K ^ + etc.

    Q18: Define Anion.

    Ans: Chemical specie which carries a negative charge. e.g. mathcal ,O ^ 2 ^ – ,C Gamma^ – etc

    Q19: What is meant by galvanic cell?

    Ans: The electrochemical cell in which a spontaneous chemical reaction takes place and generates electric current is called galvanic or voltaic cell. For example, Daniel cell

    Q20: What is half cell?

    Ans: A galvanic cell consists of two cells one having cathode while the other having anode end and which are connected with a salt bridge. Each of these known as shalf cell

    Q21: What is meant by salt bridge?

    Ans: Salt bridge is a U-shaped glass tube which consists of a saturated solution of strong electrolyte supported in a jelly type material. The ends of the U-shaped glass tube are sealed with a porous material like glass wool. The function of the salt bridge is to keep the solutions of two half cells neutral by providing a pathway for migration of ions.

    Q22: Define corrosion.

    Ans: It is a Redox reaction that takes place by the action of air and moisture with the metals. For example rusting of iron.

    Q23: What is meant by rust?

    Ans: It is a Redox reaction that takes place when iron is exposed to air and moisture. The chemical formula of rust is. F*e_{2}*O_{3} n*H_{2}*O

    Q24: Define electroplating.

    Ans: Electroplating is depositing of one metal over the other by means of electrolysis.

    Q25: Define alloy.

    Ans: Alloy is a homogenous mixture of one metal with one or more other metals or non-metals. For example stainless steel is an alloy of iron, chromium arid nickel.

    Q26: Name different types of electrochemical cells.

    Ans: The types of Electrochemical Cells are: i. Electrolytic cell. ii. Galvanic or voltaic cell.

    Q27: How the oxidation number and valency are assigned?

    Ans: Oxidation Number: While assigning oxidation number the sign precedes the number i.c. +2. For example, the oxidation number of Sodium is +1 Valency: While assigning valeney the sign followed by the number i.e. 2+, For example, the valency of sodium is 1+

    Q28: Write construction of an electrolytic cell?

    Ans: An electrolytic cell consists of a solution of an electrolyte, two electrodes (cathode and anode) that are dipped in the electrolytic solution and connected to the battery. The electrode connected to positive terminal is called anode and electrode connected to the negative terminal is called cathode.

    Q29: Who was A. Volta?

    Ans: Volta (1745-1827) was an Italian physicist known especially for the development of the first electric cell in 1800.

    Q30: Write construction of Down’s cell?

    Ans: This electrolytic cell is a circular furnace. In the center there is a large block of graphite, which acts as an anode while cathode around it is made of iron.

    Q31: Differentiate between Spontaneous and non-spontaneous reactions.

    Ans: Spontaneous reactions: Those reactions which takes place on their own without any external agent Example: Galvanic cell. Non-spontaneous reactions: Those reactions which takes place in the presence of an external agent. Example: Electrolytic cell

    Q32: Give overall reaction for the preparation of sodium hydroxide.

    Ans: 2NaCl + 2H2O→ H2 + Cl2 + 2NaOH

    Q33: Why the process of rusting does only occur on iron and not on the surface of aluminum?

    Ans: Aluminum corrodes but it does not rust. Rust refers only to iron and steel corrosion. A very hard material aluminum oxide protects the aluminum from further corrosion. In comparison to that when iron corrodes. Its color changes and produces large red flakes known as rust. Unlike aluminum oxide, the expanding and flaking of rust exposes new metal to further rusting.

    Q34: Differentiate between Strong and Weak electrolytes.

    Ans: Strong Electrolytes: The electrolyte which ionizes completely in solution is called Strong Electrolyte. It produces less ions in water Examples: NaOH, HCl etc. Weak Electrolytes: The electrolyte which do not ionize completely in solution is called Weak Electrolyte. It produces more ions in water. Examples: CH-COOH, Ca(OH)2

    Q35: What is meant by stainless steel?

    Ans: It is an alloy which is made up of iron, chromium and nickel. Which does not corrode.

    Q36: What is meant by galvanizing?

    Ans: The process of coating a thin layer of zinc on iron is called galvanizing.

    Q37: How galvanizing process takes place?

    Ans: This process is carried out t by dipping a clean iron sheet in a zine chloride bath and then heating it. After this iron sheet is removed, rolled into molten zine metal bath and finally air cooled.

    Q38: Write advantages of galvanizing.

    Ans: A major advantage of galvanizing is that zinc protects the iron against corrosion even after the coating surface is broken.

    Q39: What is the principle of electroplating?

    Ans: The principle of electroplating is to establish an electrolytic cell in which anode is made of the metal to be deposited and cathode of the object on which metal is to deposit. The electrolyte is an aqueous solution of a salt of the respective metal.

    Q40: Differentiate between Electrolytes and non-electrolytes.

    Ans: Electrolytes: The substances, which can conduct electricity in their solutions or molten states, are called electrolytes. Examples: NaOH, HCI etc. Non-Electrolytes: The substances, which cannot conduct, electricity in their solutions or molten states, are called non-electrolytes. Examples: Glucose solution, Benzene etc

    Q41: Write a note on zinc electroplating.

    Ans: A target metal is cleaned in alkaline detergent type solutions, and it is treated with acid, in order to remove any rust or surface scales. Next, the zinc is deposited on the metal by immersing it in a chemical bath containing electrolyte zinc sulphate. A current is applied which results in zine being deposited on the target metal i.e., cathode

    Q42: Write a note on tin electroplating.

    Ans: Tin usually electroplated on steel by placing the steel into a container containing a solution of tin salt. The steel is connected to an electrical circuit acting as cathode. While the 4 other electrode made of tin metal acts as anode. When an electrical current passes through the circuit, tin metal ions present in the solution deposit on steel.

    Q43: Which material is used to make cathode in electroplating?

    Ans: The cathode is made up of the object that is to be electroplated like some sheet made up of iron.

    Q44: Why is the anode made up of a metal to be deposited during electrolysis?

    Ans: When current is passed, the metal from anode dissolves in the solution and metallic ions migrate to the cathode and discharge or deposit on the cathode. ution a

    Q45: What is the difference between corrosion and rusting?

    Ans: Corrosion is slow and continuous eating away of a metal by the surrounding medium. It is a Redox chemical reaction that takes place by the action of air and moisture with metals. While, rusting is an example of corrosion. The condition for rusting is the moist air (air having water vapors in it).

    Q46: What happen to iron in the rusting process?

    Ans: The rusting process continues until all the pieces of iron is eaten up.

    Q47: Explain the role of O₂ in rusting?

    Ans: The free electrons move through iron sheet, until they reach to a region of relatively high oxygen concentration, near the surface surrounded by water layer. This region acts as cathode and electrons reduce the oxygen molecule in the presence of H ions. O2+4H++4e-2H₂O

    Q48: State the best method for protection of metal from corrosion.

    Ans: The best method for protection against the corrosion of metals exposed to acidic conditions is coating the metal. Corrosion resistant metals like Zn, Sn and Cr are used for this method.,

    Q49: Why tin-plated iron is rusted rapidly when tin layer is broken?

    Ans: When tin layer is broken and iron is exposed to the air and water, iron rusts. rapidly. a galvanic cell is established and

    Q50: Name the metal which is used for galvanizing iron?

    Ans: Zinc metal is used for galvanizing iron.

    Q51: Anode of Down’s cell is made of a non-metal, wha sits name? What is the function of this anode?

    Ans: In Down’s cell anode is made up of carbon (graphite). The CI- ions are oxidized to give Cl the anode. gas at

    Q52: Where does the sodium metal His collected in Down’s cell?

    Ans: In Down’s cell Nations are reduced at cathode and molten sodium metal floats on the denser medium salt mixture from where it is collected in a side tube.

    Q53: What is the name of the by-product produced in the Down’s cell?

    Ans: Chlorine gas is produced as a by-product in the Down’s cell.

    Q54: Are anodes of Down’s cell and Nelson’s cell made of same element? If yes, what is its name?

    Ans: Yes, anodes of both Down’s cell and Nelson’s cell are made up of same element known as graphite.

    Q55: What is the shape of cathode in Nelson’s cell? Why is it perforated?

    Ans: In Nelson’s cell, cathode is internally lined with asbestos diaphragm. Cathode is a U-shaped perforated iron from where sodium hydroxide solution slowly percolates in a catch basin.

    Q56: Which ions are discharged at cathode in Nelson’s cell and what is produced, at cathode? Ans: Cl- are discharged at cathode in Nelson’s cell and chlorine gas is evolved from that electrode.

    Q57: Why are the strong electrolytes termed as good conductors?

    Ans: Strong electrolytes are termed as good, conductors because they ionize completely in their

    Q58: Does Non-electrolyte form ions in solution?

    Ans: No, non-electrolytes do not ionize in Solution and do not allow the current to pass, through their solutions.

    Q59: Identify a strong or weak electrolyte among the following compounds.

    Ans. CuSO4 (Strong electrolyte) b. H_{2}*C*O_{3} (Weak electrolyte) c. Ca (OH) 2 (Weak electrolyte) d. HCI (Strong electrolyte) e. AgNO3 (Strong electrolyte)

    Q60: Which force drives the non-spontaneous reaction to take place?

    Ans: Non-spontaneous reactions are those which take place in the presence of external agent. This external agent is known as electrical energy.

    Q61: Which type of chemical reaction takes place in electrolytic cell?

    Ans: Non-spontaneous chemical reaction takes place with the help of electricity in electrolytic cell.

    Q62: What type of reaction takes place at anode in electrolytic cell?

    Ans: The process of oxidation takes place at anode in electrolytic cell.

    Q63: Why the positively charged electrode is called anode in electrolytic cell?

    Ans: The electrode connected to positive terminal of the battery is called anode.

    Q64: In the electrolysis of water, towards which terminal H ^ + ions move?

    Ans: In the electrolysis of water, H ^ + ions move towards cathode and reduced to hydrogen gas and liberates.

    Q65: In the electrolysis of water, where is the oxygen produced?

    Ans: In the electrolysis of water, oxygen is produced at anode electrode.

    Q66: Towards which electrode of the electrolytic cell moves the cations and what do they do there?

    Ans: In electrolytic cell, cations move towards cathode electrode and they are reduced there.

    Q68: How the half cells of a galvanic cell are connected? What is function of salt bridge?

    Ans:The half cells of a galvanic cell are connected electrically by a salt bridge. It is used to keep the solutions of two half cells neutral by providing a pathway for migration of ions.

    Q69: In the following reaction, how can you justify that H_{2}*S is oxidized and S*O_{2} is reduced? S*O_{2} + 2H_{2}*S -> 2H_{2}*O + 3S

    Ans: As hydrogen is removed from H_{2}*S therefore H_{2}*S is oxidized, while removal of oxygen takes place in S*O_{2} therefore S*O_{2} reduced.

    Q70: The reaction between MnO2 and HCl is a Redox reaction written as balance chemical equation as: MnO2 + 4HC1→ MnCl2 + 2H2O + Cl2 Then find out. a) The substance oxidized b) The substance reduced c) The substance which acts as oxidizing agent d) The substance which acts as reducing agent

    Ans: In the given balanced Chemical Equation: a) Cl is oxidized b) Mn is reduced c) MnO2 is oxidizing agent d) HCl is reducing agent

    Q71: The following reactions are Redox reaction. Find out the element which has been reduced and the element which has been oxidized. a) Zn + CuSO4→ ZnSO4 + Cu b) Cu+2AgNO3 → Cu(NO3)2 + 2Ag c) H_{2}*S + C*l_{2} -> 2HCl + S

    Ans: The Reduced and Oxidized elements are as: a) Zn. is oxidized and Cu is reduced b) Cu is oxidized and Ag is reduced c) Sulphur (s) is oxidized and Cl is reduced

    Q72: Why the following reaction is not a redox reaction, Explain with reasons? NaOH+HCI NaCl+H₂O

    Ans: Because, acid & base reactions are considered to be neutralization reactions. Whenever, acid reacts with bases, they form salt and water.

    Q73: Why the oxidation number of Oxygen in O*F_{2} is 2′

    Ans: The oxidation number of Oxygen on O*F_{2} is +2, because fluorine has. a high electronegative value as compared to oxygen. Therefore, fluorine will carry negative (-1) charge while oxygen will carry (+2) charge on it.

    Q74: An element X, has oxidation state 0. What will be its oxidation state when it gains three electrons?

    Ans: When X will gain three electrons in its valence shell its oxidation state will become X-3

    Q75: An element in oxidation state +7 gains electrons to be reduced many electrons did it accept? ed to to oxidation state +2, How

    Ans: When an element in oxidation state +7 gains electrons and reduced to that it has accepted +5 electrons in its valence shell. duced to to oxidation state +2, it shows

    Q76: If the oxidation state of an element changes from 5to – 3 Has it been reduced or oxidized? How many electrons are involved in this process?

    Ans: When the oxidation state of an n element changes from +5 to -3, it is considered to be reduced, there are eight electrons involved in this process.

    Q77: How can you justify that a reaction between magnesium and oxygen i bety while the reaction shows only addition of oxygen (oxidation)? is a Redox reaction, 2Mg + O_{2} -> 2MgO

    Ans: The above reaction is a Redox one, because oxygen tends to gain electron which is known as reduction, while magnesium tends to remove electrons which is known as oxidation. The simultaneous oxidation-reduction process is known as Redox.

    Q78: An element M reacts with another element X to form M*X_{2} in terms of loss or gain of electrons, identify the element which is oxidized and which is reduced.

    Ans: When an element M loses its electron, oxidation process takes place. When this electron is gained by element X, reduction process takes place. Therefore, element M is oxidized while element X is reduced.

    Q79: How can you justify that the following reaction is not only an oxidation reaction but also a complete Redox reaction? FeO + CO→ Fe + CO2

    Ans: When FeO reacts with CO, oxygen is removed from FeO which shows reduction process. On the other hand when oxygen is added to CO it shows oxidation process. Therefore, it is a complete redox reaction.

    Q80: Write applications of galvanic cell?

    Ans: As a result of Redox reaction, electric current is electric cur produced. The. batteries which are used for starting automobiles, running calculators and toys and to lit the bulbs work on the same principle.

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    The 9th class Punjab Textbook of Chemistry is an excellent starting point for your scientific journey. Besides this book, it’s beneficial to gather additional information from various online resources. This post provides you with the 9th Class Notes for Chemistry, including multiple posts for each chapter. Each chapter post contains a variety of questions, including Short Questions, Long Questions, and Multiple-Choice Questions.

    Be sure to like our Facebook page for educational updates from Faiz ul Islam.

    These 9th class notes are prepared according to the syllabus of all Punjab Boards, including Gujranwala Board, Lahore Board, Faisalabad Board, Multan Board, Rawalpindi Board, Bahawalpur Board, Sargodha Board, DG Khan Board, and Sahiwal Board.

  • 9th Class Chemistry Chapter 6: Solutions

    9th Class Chapter 6: Solutions Short and Simple Question & Answer

    We know you are looking for 9th class Chemistry Chapter 6 English medium notes according to the new syllabus for 2020. That’s why we have uploaded comprehensive, easy-to-understand, and precise notes for 9th class Chemistry tailored for the Punjab board session 2020-2021. You can download these notes or view them online. Many students practice 2024 Biology important questions by FAIZ UL ISLAM and get good marks in the exam.

    Q1: Define solution.

    Ans: A homogeneous mixture of two or more substances is called solution e.g. sugar dissolved in water is an example of solution.

    Q2: What are physical states of solutions?

    Ans: Solutions are found in three physical states depending upon the physical state of solvent e.g. brass is a solid solution of Zn and Cu, sea water is liquid solution and air is a gaseous solution. Liquid solutions are the most common solutions because of the most common solvent water.

    Q3: How a solution and a pure liquid is distinguished?

    Ans: A solution is distinguished from a pure liquid by evaporation the pure liquid leaves no residue, while a liquid which leaves behind a residue on evaporation is s solution.

    Q4:Brass and bronze cannot be separated by y physical means, yet it is considered a mixture why?

    Ans: Brass and bronze cannot be separated by y physical means, yet it is considered a mixture why? Because Brass or bronze shows the properties of its components and it has a variable composition.

    Q5: Why suspension and solutions do not show tyndall effect while colloids do?

    Ans: Because particles of colloids are big enough to scatter the beam of light but there is no scattering of light by particles of solution because they are so small they cannot scatter the rays but particles of suspensions are so big that light is blocked.

    Q6: What is the reason for the difference between solutions, colloidal and suspensions?

    Ans: In solution particles are very small. In colloidal solution particles are larger than solution but not enough larger as in suspension.

    Q7: Why does not the suspension form a homogeneous mixture?

    Ans: Particles in suspension remain un-dissolved and settle down after some time. Therefore suspension does not form a homogeneous mixture.

    Q8: How will you test whether given solution is colloidal solution or not?

    Ans: If there is scattering of light inside the solution, is colloidal solution. If solution does not show the tyndall effect. Then it is not colloidal solution.

    Q9: Classify the following into true solution and colloidal solution. Glucose solution, copper sulphate solution, silver nitrate solution, Blood, starch solution, toothpaste.

    Ans: True solution: Glucose solution, copper sulphate solution, silver nitrate solution Colloidal solution: Blood, starch solution, toothpaste.

    Q10: Why we stir paints thoroughly before using?

    Ans: Because paint is suspension. In suspension particles remain undissolved and settle down

    Q11: Which of the following will scatter light and why? Sugar solution, Soap solution, Milk of Magnesia.

    Ans: Sugar Solution: Sugar solution will not scatter light because particles of solution are so small they cannot scatter light. Soap Solution: Soap solution scatter the light because it is colloidal solution and its particles are enough large they can scatter light. Milk of Magnesia: Milk of magnesia cannot scatter the light because it is suspension and its particles are so big that light is blocked.

    Q12: What do you mean, like dissolves like? Explain with examples.

    Ans: Like dissolves like means polar substances are soluble in polar solvents and non-polar substances are soluble in non-polar solvents. Tonic solids and polar covalent solids are soluble in water e.g. KCl and sugar is soluble in water. Non polar substances are soluble in non-polar substances e.g. grease is soluble in ether.

    Q13: How does nature of attractive forces of solute-solute and solvent-solvent affect the solubility?

    Ans: Solubility is greater if the attractive forces between solvent-solvent are stronger similarly if the attractive forces become weaker in solute-solute then, solubility will be greater.

    Q14: How you can explain the solute-solvent interaction to prepare NaCl solution?

    Ans: When NaCl is added in water it dissolves readily because the attractive interaction between ions of NaCl and polar molecules of water are strong enough to overcome attractive forces between Na and CI in solid NaCl. In this way NaCl dissolve in water.

    Q15: Justify with example that solubility increases with increase in temperature.

    Ans: When salt like KNO3 is dissolved in water, heat is absorbed. It means heat is required to break the attractive. forces between ions of solute. Therefore, solubility of such salt increases with Increases of temperature

    Q16: What do you mean by volume/volume %?

    Ans: It is the volume in cm³ of a solute per 100cm³ of the solution.

    Q17: What is aqueous solution?

    Ans: The solution which is formed by dissolving a substance in water is called an aqueous solution.

    Q18: What is difference between solute and solvent?

    Ans: Solute: The component of solution which is present in smaller quantity is called solute. Solvent: The component of a solution which is present in larger quantity in solution is called

    Q19: Define saturated solution.

    Ans: A solution containing maximum amount of solute at a given temperature called saturated solution.

    Q20: Define unsaturated solution.

    Ans: A solution which contains lesser amount of solute than that which is required to saturate it at a given temperature is called unsaturated solution.

    Q21: Define supersaturated solution.

    Ans: The solution that is more concentrated than a saturated solution is known as supersaturated solution.

    Q22: What is difference between dilute and concentrated solution?

    Ans: Dilute Solution: Dilute solutions are those which contain relatively small amount of dissolved solute in the solution. Concentrated Solution: Concentrated solutions are those which contain relatively large amount of dissolved solute in the solution are called concentrated solutions.

    Q23: What is concentration?

    Ans: Ratio of amount of solute to the amount of solution or amount of solute to the amount of solvent.

    Q24: Define solubility.

    Ans: Solubility is defined as the number of grams of the solute dissolved in 100g of solvent to prepare a saturated solution at a particular temperature.

    Q25: Define colloid.

    Ans: Colloids are solutions in which the solute particles are larger than those present in the true solution but not large enough to be seen by naked eye, for example blood.

    Q26: Define suspension.

    Ans: Suspension is a heterogeneous mixture of undissolved particles in a given medium, for Example Chalk in water.

    Q27: Why solubility of L*I_{2}*S*O_{4} and C*e_{2}(S*O_{4}) decreases with the increase of temperature?

    Ans: L*I_{2}*S*O_{4} and C*e_{2}(S*O_{4}) dissolve in water with the evolution of heat, therefore solubility of such salts decreases with the increases of temperature.

    Q28: Why solution is considered mixture?

    Ans: Because components of solution can be separated by physical means.

    Q29: Distinguish between the following pairs as compound or solution. Water and salt solution Carbonated water and acetone Vinegar and benzene

    Ans: Water and salt solution, water is compound and salt solution is solution Vinegar is solution and benzene is compound Carbonated water is solution and acetone is compound

    Q30: What is the major difference between a solution and a mixture?

    Ans: A solution is always homogeneous but mixture may be homogeneous or heterogeneous.

    Q31: Why alloys are considers solutions?

    Ans: Because alloys are also homogeneous mixture

    Q32: Dead sea is so rich with salt that it forms crystals when temperature lowers in winter. Can you comment why is it named as dead sea?

    Ans: Because it does not support life.

    Q33: Does the percentage calculation require the chemical formula of the solute? requ

    Ans: No. chemical formula is not required.

    Q34: You are asked to prepare 15 percent (w / w) solution of common vale How much amount of water will be required to prepare this solution.

    Ans: 85g of water is required to prepare this solution.

    Q35: How much water should be mixed with 18c * m ^ 3 of alcohol so as to obtain 18% (v / v) alcohol solution?

    Ans: 18c * m ^ 3 of alcohol is dissolved in sufficient amount of water so that the total volume of the solution become 100c * m ^ 3

    Q36: Which one of the following is more concentrated one molar or three molars?

    Ans: Three molars

    Q37: What will happen if the solute-solute forces are stronger than those of solute-solvent forces?

    Ans: Solute will not dissolve in the solvent.

    Q38: When solute-solute forces are weaker than those of solute-solvent forces? Will solution form?

    Ans: Solute will dissolve and solution will form.

    Q39: Why is iodine soluble in CCl4 and not in water?

    Ans: Because iodine is non-polar in nature and CCl4 is also non-polar but water is polar. Q40: Why test tube become cold when KNO; is dissolved in water? Ans: Because when KNO3 is dissolved in water heat is s absorbed from the surrounding. om the s

    Q41: What is difference between colloid and suspension?

    Ans: Colloid: In colloid particles are larger than those present in the true solution. Suspension: Suspension is a heterogeneous mixture of undissolved particles in given medium.

    Q42: Can colloids be separated by filtration, if not why?

    Ans: Not, because particles are not so big.

    Q43: Why are the colloids quite stable?

    Ans: Because particles do not settle down for a long time.

    Q44: Why does the colloid show tyndall effect?

    Ans: Because their particles scatter the path of light rays.

    Q45: What is tyndall effect and on for what factor it depends?

    Ans: The scattering of beam of light by particles of colloids is called tyndall effect. It depends up the size of particles.

    Q46: Identify as colloids or suspension from the following: Paints, milk, milk of magnesia, soap solution.

    Ans: Suspension: Paints, milk of magnesia Colloids Soap solution, milk

    Q47: How can you justify that milk in colloid?

    Ans: Milk is colloid because it shows tyndall effect.

    Download PDF Format

    The 9th class Punjab Textbook of Chemistry is an excellent starting point for your scientific journey. Besides this book, it’s beneficial to gather additional information from various online resources. This post provides you with the 9th Class Notes for Chemistry, including multiple posts for each chapter. Each chapter post contains a variety of questions, including Short Questions, Long Questions, and Multiple-Choice Questions.

    Be sure to like our Facebook page for educational updates from Faiz ul Islam.

    These 9th class notes are prepared according to the syllabus of all Punjab Boards, including Gujranwala Board, Lahore Board, Faisalabad Board, Multan Board, Rawalpindi Board, Bahawalpur Board, Sargodha Board, DG Khan Board, and Sahiwal Board.

  • 9th Class Chemistry Chapter 5: Physical States of Matter

    9th Class Chapter 5: Physical States of Matter Short and Simple Question & Answer

    We know you are looking for 9th class Chemistry Chapter 5 English medium notes according to the new syllabus for 2020. That’s why we have uploaded comprehensive, easy-to-understand, and precise notes for 9th class Chemistry tailored for the Punjab board session 2020-2021. You can download these notes or view them online. Many students practice 2024 Biology important questions by FAIZ UL ISLAM and get good marks in the exam.

    Q1: Define flatter.

    Ans: For Everything which occupies some space and has mass is called matter Air, Wood, H2SO4 etc

    Q2: Write down the names of different states of matter.

    Ans: There are three states of matter i) Solid ii) Liquid iii) Gas

    Q3: Describe gaseous state of matter.

    Ans: Matter in gaseous state does not have definite shape and volume. Therefore, cases occupy all the available space. Gases have very weak intermolecular forces.

    Q4: Define Diffusion. On what factor diffusion of gases depends?

    Ans: Diffusion is spontaneous mixing up of molecules by random motion and collisions to form a homogeneous mixture. Factors: Rate of diffusion depends upon the molecular mass of the gas.

    Q5: Define Effusion. On what factor it depends?

    Ans: It is escaping of gas molecules through a tiny hole into a space with lesser pressure. Example: when a tyre gets punctured air effuses out. Factor: Effusion depends upon the molecular masses of gases.

    Q6: Define Pressure. Writes down its Sl unit.

    Ans: Pressure: The force (F) exerted per unit surface area (A) S.I unit of pressure: The SI unit of force is Newton and that of area is m². Hence pressure has Sl unit of Nm². It is also called Pascal (Pa):

    Q7: Write down the name of instruments with the help of, we measure the pressure?

    Ans: There are two instruments with the help of we measure the pressure: Barometer: Barometer is used to measure the atmosphere pressure ii) Manometer: It is used to measure the pressure in laboratory.

    Q8: Define standard atmospheric pressure.

    Ans: It is defined as the pressure exerted by mercury column of 760mm height of sea level. It is sufficient pressure to support a column of mercury in height at sea level.

    Q9: How Cases are compressible?

    Ans: Cases are highly compressible due to empty spaces een their molecules.

    Q 10: Describe the mobility of gas molecules.

    Ans: Gas molecules are always in state of continuous motion. They can move from one place to another because gas molecules possess very high kinetic energy. of continue

    Q 11: Describe the density of gases.

    Ans: Density is the ratio of mass and volume (m/v). Gases have low density than liquid and solids. Density of gases is expressed in grams per dm³

    Q 12: Why the rate of diffusion of gases is rapid than that of liquid?

    Ans: Because gas molecules have insignificant intermolecular forces as compared to liquid. So the rate of diffusion of gases is rapid than that of liquid.

    Q 13: What do you mean by Pascal? How many Pascal are equal to 1-atm?

    Ans: Pascal is the SI unit of pressure One Pascal=1 Nm-2

    Q 14: Whether the density of a gas decrease on cooling.

    Ans: The density of gases increases by cooling because their volume decreases. For example, at nominal atmospheric pressure the density of oxygen gas is 1.4 gdm³ at 20 deg * C mid 1.5 gdm³ at 0 deg * C

    Q 15: Why is the density of gas measured in gmdm³, while that of a liquid is expressed in gcm³?

    Ans: Gases have low densities due to light mass and more volume occupied by the gas molecules. That is why gas density is expressed in grams per d * m ^ 3 whereas liquid and solid densities are expressed in gram per c * m ^ 3 because liquids and solid are 1000 times denser than gases.

    Q 17: Define Boyle’s law.

    Ans: Volume of a given mass of a gas is inversely proportional to its pressure provided the temperature remains constant

    Q18: Who was Robert Boyle?

    Ans: Robert Boyle (1627-1691) was natural philosopher, chemist, physicist and inventor. He is famous for Boyle’s law of gases.

    Q 19: Is the Boyle’s law applicable to liquids?

    Ans: No, Boyle’s law only applicable on gas.

    Q 20: Is the Boyle’s law valid at very high temperature?

    Ans: No. it is only valid at constant temperature.

    Q 21: What will happen if the pressure on a sample of gas is raised three times and its temperature is kept constant’?

    Ans: If the pressure on a simple gas is raised three times s at constant temperature, the volume will also decrease three times of its original volume.

    Q 22: Who was J. Charles?

    Ans: J. Charles (1746-1823) was a French inventor, described in 1802, how gases tend to expand mathematician and balloonist. He heated.

    Q 23: Define Charles law.

    Ans: J. Charles in 1789 presented his law that “the volume of a given mass of a gas is directly proportional to the absolute temperature if the pressure is kept constant”.

    Q 24: What is absolute temperature scale?

    Ans: Lord Kelvin introduced absolute temperature scale or Kelvin scale. This scale of temperature starts from O-K (-273.15°C) which is given the name of absolute zero. It is the temperature at which an ideal gas would have zero volume.

    Q 25: Which parameters are kept constant in Charles’s Law?

    Ans: In Charles law pressure remains constant.

    Q 26: Why volume of gas decreases with increase of pressure?

    Ans: The volume of gas decreases with increase of pressure because pressure and volume both are inversely proportional to each other so when we increase pressure, volume will decrease and when volume increases, pressure decreases.

    Q 27: Does Kelvin scale show a negative temperature?

    Ans: The Kelvin scale does not show negative value as O-K = -273°C

    Q 28: When a gas, is allowed to expand, what will be its effect on its temperature?

    Ans: Temperature will be increased because volume and temperature is directly proportional to each other.

    Q 29: Can you cool a gas by increasing its volume?

    Ans: Yes, by sudden increasing the volume of a gas, it gives the cooling effect.

    Q 30: In which units body temperature is measured?

    Ans: Body temperature is measured in Fahrenheit and is equivalent to 37°C. This temperatu temperature. Normal body temperature is 98.6F. close to average normal atmospheric

    Q 31: What is meant by liquid.

    Ans: Matter that has indefinite shape but a definite volume is called liquid. For example, Water, milk etc.

    Q 32: Define evaporation. On which factors it depends.

    Ans: The Process of escaping molecules spontaneously mom the surface of a liquid is called evaporation. It depends upon following factors. 1.Temperature 2.Surface tension 3.intermolecular forces

    Q 33: Explain evaporation causes cooling.

    Ans: When the high kinetic energy molecules vaporize the temperature of remaining molecules falls down. To compensate this deficiency of energy, the molecules of liquid absorb energy from the surrounding. As a result, the temperature of surrounding decreases and we feel cooling.

    Q 34: Define vapour pressure.

    Ans: The pressure exerted by the vapour of a liquid at equilibrium with the liquid at a particular temperature is called vapour pressure of a liquid.

    Q 35: Write down the names of factors on which vapour pressure depends.

    Ans: There are following factors: i) Nature of liquid ii) Size of molecule iii) Temperature

    Q 36: Define boiling point.

    Ans: The temperature at which the vapour pressure on its surface is called boiling point. dis equal to atmospheric pressure

    Q 37: Write down the names of factors which boiling point depends.

    Ans: The factors on which boiling point depends are: Nature of liquid Intermuscular forces External pressure.

    Q 38: Define freezing point.

    Ans: Freezing point of a liquid is that temperature at which vapour pressure of liquid phase is equal to the vapour pressure of the solid phase. At this temperature liquid and solid coexist in dynamic equilibrium with one another.

    Q 39: Define diffusion. In which factors diffusion of liquid depends?

    Ans: “The spontaneous movement of molecules from the region tit higher concentration of the region of lower concentration is called diffusion” Factors: diffusion depends upon following factors. 1.intermolecular forces 2.Size of molecules 3.Shape of molecules

    Q 40: Describe density of liquid.

    Ans: The density of liquid depends upon its mass and volume. Liquid are denser than gases because molecules of liquids are closely packed anal spaces between their molecules all negligible. The density of liquid is expressed in the gram per cm³.

    Q 41: Why does evaporation increase with increase in temperature?

    Ans: the evaporation increases with increase in temperature because kinetic energy of the molecules increases with increase in temperature. This K.E is so high that they overcome the intermolecular forces and evaporation rapidly.

    Q 42: What do you mean by condensation?

    Ans: The process of moving the molecules from the is called condensation. pours phase back into the liquid phase

    Q 43: Why the vapour pressure eis higher at high temperature?

    Ans: At high temperature the vapour pressure is higher than aa low temperature. When temperature increases the kinetic energy of the molecules increases enough to enable them to vaporize and exerts pressure so the vapour pressure increases at high temperature

    Q 44: Why the boiling point of water is higher than of alcohol?

    Ans: The boiling Point of water is higher than of alcohol because water has stronger inter molecular forces.

    Q 45: What do you mean by dynamic equilibrium?

    Ans: When the rate of evaporation becomes equal to rate of condensation at stage, the number of molecules evaporating will be equal to the number of molecules coming back to liquid. This state is called dynamic equilibrium.

    Q 46: Why arc the rate of diffusion in liquid slower than that of gas?

    Ans: The rate of diffusion in liquid slower than that of gas because liquid has stronger intermolecular forces, as compared to gases so the rate of diffusion is slower than that of gases.

    Q 47: Why does the rate of diffusion increase with increase in temperature?

    Ans: Diffusion increases by increasing temperature because at high temperature the intermolecular forces are weak, so rate of diffusion increases.

    Q 48: Why liquids are mobile.

    Ans: The ease of flow of liquid is called mobility. Because the ease of flow of liquid depends upon the strength of intermolecular attractive forces, the weaker the strength of these forces, the more mobile is the liquid and vice versa. Due to this mobility of molecules, liquid can be poured from one vessel in another ves

    Q 49: What is meant by solid?

    Ans: Matter that has a definite shape and plastic etc. is called solid. for example, wood, coal,

    Q 50: Define melting point.

    Ans: The temperature at which a solid substance is converted into a liquid is called melting point of the solid substance.

    Q 51: Explain the rigidity of solid.

    Ans: The particles of solids are not mobile. They have fixed positions. Therefore, solids are rigid in their structure.

    Q 52: Explain density of solid.

    Ans: Solids are denser than liquids and gases because solid particles are closely packed and do not have empty space between their particles. So, they have high density as compare to liquid and gases.

    Q 53: Define amorphous solids. Give example.

    Ans: Amorphous solids means shapeless solid in which the particles are not regularly arranged or their regular shapes are destroyed.

    Q 54: Define crystalline solids. Give example.

    Ans: Solids in which particles are arranged in a definite three dimensions pattern are called crystalline solids. Example: Diamond, sodium chloride etc.

    Q 55: Define allotropy and give any two examples.

    Ans: The Phenomenon in which an element exists in different forms having different physical properties but same chemical properties is called allotropy. Examples: (i) Carbon has three allotropic forms e.g., Diamond, Graphite and Bucky balls. (ii) Sulphur has two allotropic forms e.g. Rhombic sulphur and Monoclinic sulphur.

    Q 56: Define transition temperature.

    Ans: The temperature at which one allotrope changes into another is called transition temperature.

    Q 57: In which form of sulphur exists at room temperature?

    Ans: Rhombic Sulphur exists on room temperature.

    Q 58: Why is white tin available at room temperature?

    Ans: The transition temperature of two allotropic forms of tin is 18°C. So, this temperature indicates white tin is more stable above 18°C.

    Q 59: Why the melting point of a solid is considered its identification characteristics?

    Ans: Because the solid particle possess only vibrational kinetic energy. When solids are heated their vibrational energies increases and particles vibrate at their mean position with a high speed.

    Q 60: Which is lightest one, aluminum or gold?

    Ans: Aluminum is lighter than gold because the density of aluminum is lesser than gold. For example, density of aluminum is 2.70 gcm³ and gold is 9.3 gcm³.

    Q 61: Write the molecular formula of a sulphur molecule?

    Ans: Formula of sulphur molecule is Sg.

    Q 62: Which allotropic form of carbon is stable at room temperature (25°C)?

    Ans: Diamond, graphite and Bucky balls are Stable forms of carbon at room temperature. Among these allotropic forms, graphite is energetically slightly more stable than diamond.

    Q 63: State whether allotropy is shown by elements or compounds or both.

    Ans: Allotropy is shown by only elements because the existence of tin element in more than one forms in same physical state, tan the other hand compound do not show this property her hand

    Q 64: What is diffusion? Explain with an example.

    Ans: The spontaneous movement of molecules from the region of higher concentration to the region of lower concentration is called diffusion. Example: For example, when a few drops of ink are added in a beaker of water, ink molecules move around and after a while spread in whole of the beaker.

    Q 65: Define standard atmospheric pressure. What are its units? How it is related to Pascal?

    Ans: It is the pressure exerted by the atmosphere at the sea level. It is the pressure exerted by a mercury column of 760mm height at sea level.

    Q 66: What do you mean by evaporation? How it is affected by surface area? Ans: The press of a liquid into a gas phase is called evaporation. Evaporation is a surface phenomenon. Greater is the surface area greater is evaporation and vice versa.

    Q 67: In which form sulphur exists at 100°C

    Ans: Sulphur exists in monoclinic form at 100°C.

    Q 68: What is the relationship between evaporation and boiling point of a liquid?

    Ans: A figured having higher boiling point will have slow evaporation due to stronger inter interlecular forces. A liquid having low boiling point will have faster evaporation.

    Download PDF Format

    The 9th class Punjab Textbook of Chemistry is an excellent starting point for your scientific journey. Besides this book, it’s beneficial to gather additional information from various online resources. This post provides you with the 9th Class Notes for Chemistry, including multiple posts for each chapter. Each chapter post contains a variety of questions, including Short Questions, Long Questions, and Multiple-Choice Questions.

    Be sure to like our Facebook page for educational updates from Faiz ul Islam.

    These 9th class notes are prepared according to the syllabus of all Punjab Boards, including Gujranwala Board, Lahore Board, Faisalabad Board, Multan Board, Rawalpindi Board, Bahawalpur Board, Sargodha Board, DG Khan Board, and Sahiwal Board.

  • 9th Class Chemistry Chapter 4: Structure of Molecules

    9th Class Chapter 4: Structure of Molecules Short and Simple Question & Answer

    We know you are looking for 9th class Chemistry Chapter 4 English medium notes according to the new syllabus for 2020. That’s why we have uploaded comprehensive, easy-to-understand, and precise notes for 9th class Chemistry tailored for the Punjab board session 2020-2021. You can download these notes or view them online. Many students practice 2024 Biology important questions by FAIZ UL ISLAM and get good marks in the exam.

    Q1. Why atoms form a chemical bond?

    Ans: Atoms form a chemical bond to achieve stability by acquiring inert gas electron configuration.

    Q2. Why noble gases are non-reactive in nature?

    Ans: The noble gases do have 2 or 8 electrons in their valence shells. It means that all the noble gases have their valence shell completely filled. Their atoms do not have vacant space in their valence shell to accommodate extra electrons. Therefore, noble gases do not gain, lose or share electrons. That is why they are non-reactive, at ordinary conditions.

    Q3. How an atom can accommodate eight electrons in its valence shell?

    Ans: An atom can accommodate eight electrons in its valence shell in three ways: a) By giving valence shell electrons (if they are less than four) to other atoms. b) By gaining electrons from other atoms (if the valence shell has five or more electrons in it. c) By sharing valence electrons with ectrons toms.

    Q4. When atoms are considered to be unstable?

    Ans: The atoms having less than 2 or 8 electrons in their valence shells are unstable.

    Q5. What is the mode of reaction of an atom with reference to their group?

    Ans: Mode of reaction of an atom depends upon its number of valence shell electrons. For example, group I has only | electron in its valence shell and group 17 has 7 electrons in its valence shell.

    Q6. What is meant by a chemical bond?

    Ans: A force of attraction between atoms that holds them together in a molecule is called a chemical bond.

    Q7. What is meant by duplet rule?

    Ans: The attaining of two electrons in the outermost shell by sharing, by losing or by gaining electrons is called duplet rule.

    Q8. What is meant by octet rule?

    Ans: The attaining of eight electrons in the outermost shell by sharing, by losing or by gaining electrons is called octet rule.

    Q9. What would be the effect, when two approaching atoms come closer to each other?

    Ans: When two approaching atoms come closer, the attractive as well as repulsive forces become operative.

    Q10. What is the effect of attractive and repulsive forces in the formation of a chemical bond?

    Ans: If attractive forces become dominate, the decrease in the energy of the system takes place, due to which chemical bond is formed. While, if repulsive forces become dominate, the increase in the energy of the system takes place, due to which no chemical bond is formed.

    Q 11. What is meant by bonding electrons?

    Ans: The valence electrons, which are involved in chemical bonding, are termed as bonding electrons.

    Q 12. Name different types of chemical bonds

    Ans: These are types of Chemical bonds a) Ionic bond. b) Covalent bond c) Co-ordinate covalent bond d) Metallic bond

    Q 13. Define ionic bond.

    Ans: The bond formed by the complete transfer of electrons from one atom to another is called ionic bond.

    Q 14. What is meant by covalent bond?

    Ans: The bond formed by the mutual sharing of pairs of electrons is called covalent bond.

    Q 15. What is meant by single covalent bond? Give example.

    Ans: When one electron is contributed by each bonded atoms, one bond pair is formed and it forms a single covalent bond. It is represented by (-). A few examples of molecules with single covalent bonds are hydrogen, chlorine, hydrochloric acid, methane etc.

    Q 16. What is meant by double covalent bond? Give example.

    Ans: When each bonded atom contributes two electrons, two bond pairs are shared and a double covalent bond is formed. It is represented by (=). A few examples of molecules with double covalent bonds are oxygen, ethene etc.

    Q 17. What is meant by triple covalent bond? Give example.

    Ans: When each bonded atom contributes three electrons, three bond pairs are involved in bond formation. This type is called triple covalent bond. It is represented by (=). A few examples of molecules with triple covalent bonds are nitrogen, ethyne etc.

    Q 18. What is meant by bond pair?

    Ans: The electrons that pair up to form a chemical bond is called bond pair electrons.

    Q 19. What is meant by lone pair?

    Ans: A non-bonded electron pair available on an atom is termed as lone pair of electron.

    Q 20. Describe Lewis structure diagram.

    Ans: The electronic configuration of the valence shells of atoms is shown in small ‘dots’ or ‘crosses’ around the symbol of the element. Each dot or cross represents an electron. This is a standard method of Lewis to describe the electronic configuration of valence shell of an atom. It is called Lewis structure diagram.

    Q 21. Define coordinate covalent bond.

    Ans: A type of covalent bond in which the bond pair of electrons only is called coordinate covalent or dative covalent bond

    Q 22. What is meant by non-polar covalent bond? Give example. Ans: If a covalent bond formed between two similar atoms, the shared pair of electrons is attracted by both atoms equally. Such type of bond is called non-polar covalent bond. A few examples of molecules with non-polar covalent bonds are hydrogen, chlorine, nitrogen etc.

    Q 23. What is meant by polar covalent bond? Give example.

    Ans: If a covalent bond formed between two different types of atoms, then the bond pair of electrons will not be attracted equally by the bonded atoms. Such type of bond is called polar covalent bond. A few examples of molecules with polar covalent bonds are hydrochloric acid, water etc.

    Q 24. What is meant by electronegative atom?

    Ans: The atom will attract the bond pair of electrons more strongly than the other one during polar covalent bond formation. This atom will be called as more electronegative atom as compared to the other bonded atom. For example, in HCI molecule Cl is more electronegative atom as compared to H atom.

    Q 25. Give the formation of polar covalent bond in HCI molecule.

    Ans: The difference between electro-negativities of hydrogen and chlorine is 1.0. As the electronegativity of chlorine is more, it attracts the shared pair of electron towards itself with a greater force. A partial negative charge is therefore created on chlorine and in turn a partial positive charge on hydrogen due to electronegativity difference. It creates polarity in the bond and is called a polar covalent bond.

    Q 26. What do you mean by delta sign and why it develops?

    Ans:The delta (8) sign indicates partial positive or partial negative charge that is developed due to unequal sharing pair or bonded pair of electrons.

    Q27. What is the effect of electronegativity in the formation of an ionic bond?

    Ans: By using electronegativity values, it is possible to predict whether a chemical bond will be ionic or a covalent in nature. A bond formed between elements of high electronegativity (halogen group) and elements of low electronegativity (alkali metals) are ionic in nature.

    Q 28. How electronegativity values help p us us to to predict predic the formation of a chemical bond?

    Ans: If the difference of electronegativities between two elements is more than 1.7 the bond between them will be predominately ionic bond and if it is less than 1.7, the bond between two atoms will be predominately covalent.

    Q 29. What is meant by metallic bond?

    Ans: A bond formed between metal atoms (positively charged ions) due to mobile or free electrons is called metallic bond.

    Q 30. What is meant by intermolecular forces?

    Ans: A weak force of attractions formed between two molecules is called intermolecular forces

    Q 31. What is meant by Van der Waals forces?

    Ans: All intermolecular forces, which are collectively called Van der Waals forces, are electrical in nature. They result from the attractions of opposite charges which may be temporary or permanent.

    Q 32. How dipole-dipole interactions are found in HCl molecule?

    Ans: When partial positive and partial negative charges exist at different positions in a molecule, the adjacent molecules will arrange themselves in such a way that negative portion of that molecule come near to positive portion of other molecule. It results in net forces of attraction between oppositely charged portions of two adjacent molecules. These attractive forces are called dipole-dipole interactions as represented in HCl are as:

    Q 33. What is meant by hydrogen bonding?

    Ans: A bond formed between partially positive hydrogen atom of one molecule with partially negative atom of the other molecule is called hydrogen bonding.

    Q 34. What are ionic compounds? Give example, e

    Ans: Those compounds which contain ionic bond NaCl, KCI etc. ionic bon in them are known as ionic compounds. e.g.,

    Q 35. Write any two properties of ionic compounds.

    Ans: Two important properties of ionic compounds are as: 1. They are made up of positively and negatively charged ions. ii. They are are consist of ions not the molecules.

    Q 36. Ionic solids are good conductors of electricity. Why?

    Ans: Ionic solids are good conductors of electricity only in solution and in the molten form due to the presence of free ions in them.

    Q 37. When covalent compounds are considered to be a good conductor of electricity?

    Ans: They are considered to be good conductors of electricity due to having polar character in their bonding when they are dissolve in polar solutions.

    Q 38. Why coordinate covalent compounds do not form ions in water?

    Ans: They do not form ions in water because the nuclei in these compounds are held by shared electrons.

    Q 39. What is meant by malleability and ductility?

    Ans: Malleability is the property by virtue of which a metal can be drawn into sheets, while ductility is the property by value of which a metal can be drawn into wires.

    Q 40. Name polymers or resins used in synthetic adhesives.

    Ans: Polymers or resins used in synthetic adhesives are: i. Thermoplastics ii. Thermosets

    Q 41. Give composition of epoxy.

    Ans: Epoxy is polymer that is formed from two different chemicals i) Resin. ii) Hardener.

    Q 42. Give uses of adhesives.

    Ans: These highly performance adhesives are used in the constru n of Aircrafts, Automobiles, Bicycles, Boats, Golf clubs etc

    Q 43. What are the applications of epoxy adhesives?

    Ans: They can be made flexible or rigid, transparen setting. opaque, colored as well as fast or slow

    Q 44. What properties show presence of different types of chemical bond between atoms of of different metals?

    Ans: The different properties shown by metals such as high melting and boiling points, good conductions of heat and electricity, hard and heavy nature, suggest existence of different type of chemical bond between atoms of metals.

    Q 45. How metallic bond is formed?

    Ans: In metals, the hold of nucleus over the outermost electrons is weak because of large sized atoms and greater number of shells in between nucleus and valance electrons. Because of low ionization potentials, metals have the tendency to lose their outer electrons easily. Due to which, these loose or free electrons of all metal atoms move freely in the spaces between atoms of a metal. The nuclei of metal atoms appear submerged in sea of free mobile electrons. These mobile electrons are responsible for holding the atoms of metals together forming a metallic bond.

    Q 46. Why does sodium form a chemical bond with chlorine?

    Ans: Sodium forms a chemical bond with chlorine due to the following reasons: i. Sodium has the tendency to lose one electron and chlorine has the tendency to gain one electron. This favors the transference of electrons and hence ionic bond is formed. ii. Sodium is electropositive and is at high energy state whereas chlorine is electronegative and is sat low energy state. This energy difference favors the formation of ionic bond between them.

    Q 47. Why sodium does lose an electron and attains +1 charge?

    Ans: Sodium has the electronic configuration as followst n * 1Na = 1s ^ 2 2s ^ 2 2p ^ 6 3s ^ 1 Hence, it is better and easier for sodium to lose one electron and complete its valence shell rather than gaining seven electrons to complete its octet.

    Q 48. How do atoms follow octet rule?

    Ans: Most of the atoms or elements in the periodic table gain stability by having eight electrons in their valence shell. They do so it by gaining, sharing or losing electrons. This is how they follow octet rule. They attain the electronic configuration of nearest noble gas

    Q 49. Which electrons are involved I in chemical bonding?

    Ans: Only the electrons present in the valence shell of an atom are involved in chemical bonding. All the other electrons do not take part in chemical bonding

    Q 50. Why does group 1 elements prefer to combine with group 17 elements?

    Ans: Group elements are good losers of electrons and have low ionization energies. Group-17 elements are good gainers of electrons and have high electron affinities. Therefore, as these parameters favor the formation of bond between the two a strong ionic bond is formed between group-1 and group-17 elements

    Q 51. What type of elements have tendency of sharing of electrons?

    Ans: The elements with electronegativity values less than 1.7 show tendency of sharing electrons between them.

    Q 52. If repulsive forces dominate to attractive forces, will a covalent bond form?

    Ans: When the repulsive forces dominate the attractive forces, a bond will not be formed. This is due to the fact that repulsive forces account for increase in energy. Bond is formed when the atoms are at a state of minimum energy. As repulsive force will increase energy, so a covalent bond will not be formed.

    Q 53. Considering the electronic configuration of nitrogen atom, how many electrons are involved in bond formation and what type of covalent bond is formed?

    Ans: The electronic configuration of Nitrogen is / V / N = 1s ^ 2, 2s ^ 2, 2p ^ 3 The valence shell of nitrogen is deficient of three electrons. These two nitrogen atoms share their three valence electrons each to form a triple covalent bond with three pairs of electrons and six electrons as a total shared.

    Q 54. Point out the type of covalent bonds in the following molecules C*H_{4} C_{2}*H_{4} H_{2} N_{2} and O_{2}

    Ans: C*H_{4} : Single covalent bond C_{2}*H_{4} : Double covalent bond H_{2} : Single covalent bond N_{2} : Triple covalent bond O_{2} : Double covalent bond

    Q 55.What is lone pair? How many lone pairs of electrons are present in nitrogen and ammonia?

    Ans: The pair of electrons in the valence shell of an atom which does not take part in chemical bonding is called lone pair electrons. In nitrogen there are two lone pairs and on each atom a lone pair is present. In ammonia, there is only one lone pair present on nitrogen atom while hydrogen does not have any lone pair.

    Q 56. What types of electron pairs make a molecule good donor?

    Ans: Lone pair of electrons makes a molecule a good donor. Since, they are not involved in bonding, so they can be used as form further bonds e.g. In ammonia, there is one lone pair on nitrogen which forms a coordinate covalent bond with another hydrogen forming ammonium ion.

    Q 57. What is the difference between bonded and lone pair of electron and how many bonded pair of electrons is present in NH3 molecule?

    Ans: Valence shell electron pair involved in chemical bonding is a bond pair and one not involved is the lone pair of electrons and can form further bonds in certain cases. Three pairs of bonded electrons are present in NH3 as there are three single covalent bonds in ammonia molecule between one nitrogen and three hydrogen atoms.

    Q 58. Why does oxygen molecule not form a polar covalent bond?

    Ans: In oxygen molecule (O2) two oxygen atom are covalently bonded to each other. As the atoms are similar, the electronegativity difference is zero, and the electron pairs are equally shared between them. Hence, there is no polarity in the bond.

    Q 59. Why water molecule form a polar covalent bond?

    Ans: Oxygen is a highly electronegative atom as compared to hydrogen. So, during the mutual sharing, the electron pair is attracted more towards oxygen and it acquires a partial negative charge and a partial positive charge develops on hydrogen. Hence, poles are created and he covalent bond becomes polar.

    Q 60. What type of elements form metallic bonds?

    Ans: Metallic bonds consist of sea of mobile electrons with positive ions. They are present in elements which have loosely bound electrons that do not remain in the valence shell and leave the atom to form a sea of electrons. Such a structure is observed usually in metals e.g., sodium, iron in metals.

    Q 61. Why in metals the hold of nucleus over the outermost electrons is weak? Give reason.

    Ans: The hold of nucleus on the outermost electrons in metals is very weak because of the increased screening effect or shielding effect between the intervening electrons which tend to decrease the force of attraction between nucleus and the electrons. Distance also plays the same role. As the electrons are at a greater distance from nucleus, the force of attraction becomes weak. ]

    Q 62. Why the electrons move freely in metals?

    Ans: Because, the hold of nucleus over the outermost electrons is weak because of large sized atoms and greater number of shells in between nucleus and valence electrons. Furthermore, because of low ionization potentials, metals have the tendency to lose their outer electrons’ easily. Resultantly, these loose or free electrons of all metal atoms move freely in free space between atoms of a metal.

    Q 63. Which types of electrons are responsible for holdings the atom together in metals?

    Ans: The mobile electrons are responsible for holding the atoms of metals together forming a metallic bond.

    Q 64. Why a dipole develops in a molecule?

    Ans: The unequal sharing of electrons between two different types of atoms make one end of molecule slightly positive and other end slightly develops in a molecule. tively charged. Hence a dipole

    Q 65. What do you mean by dipole induced forces?

    The positive end of polar molecule attracts the mobile electrons of the nearby neén- polar molecule. In this way polarity is introduced i in non-polar molecule and both become dipoles. These forces are called e called dipole induced forces.

    Q 66. Why dipole forces of attraction are not found in halogen molecules?

    Ans: Halogen molecules form a non-polar covalent ‘bond between them. In order to make non- polar bonds, no electronegative difference of elements is required, due to which dipole forces do not formed in halogen molecules:

    Q 67. What types of attraction forces exist between HCI molecules? Ans: Weak intermolecular forces exist between HCI molecules.

    Q 68. Why ionic compounds have high melting and boiling points?

    Ans: As ionic compounds are made up of positive and negative ions, there exist strong electrostatic forces of attraction between oppositely charged ions. So, a great amount of energy is required to break these forces, therefore ionic compounds have high melting and boiling points.

    Q 69. Why ionic compounds are easily soluble in water?

    Ans: Water has high dielectric constant that weakens the attraction between the ions of ionic compounds due to which they are easily soluble in water

    Q 70. What type of attractive forces exists in ionic compounds?

    Ans: Ionic bond exists in ionic compounds.

    Q 71. Why the covalent compounds of bigger size molecules have high melting points?

    Ans: Bigger molecules with three dimensional bonding forms covalent crystals which are very stable and hard due to which they have high melting and boiling points.

    Download PDF Format

    The 9th class Punjab Textbook of Chemistry is an excellent starting point for your scientific journey. Besides this book, it’s beneficial to gather additional information from various online resources. This post provides you with the 9th Class Notes for Chemistry, including multiple posts for each chapter. Each chapter post contains a variety of questions, including Short Questions, Long Questions, and Multiple-Choice Questions.

    Be sure to like our Facebook page for educational updates from Faiz ul Islam.

    These 9th class notes are prepared according to the syllabus of all Punjab Boards, including Gujranwala Board, Lahore Board, Faisalabad Board, Multan Board, Rawalpindi Board, Bahawalpur Board, Sargodha Board, DG Khan Board, and Sahiwal Board.