Cbse 8th std physics note sound

 1. Sound is defined as a form of energy that travels through medium in the form of vibrations.

2. A sound can be produced by:

• beating
• rubbing
• blowing
• plucking

3. The movement that produces sound in rapid to and fro motion is called vibration.

4. Sound requires medium to travel. Sound can travel through solids, liquids and gases but not through vacuum.

4. Sound requires medium to travel. Sound can travel through solids, liquids and gases but not through vacuum.

5. Sound travel fastest in solid and slowest in gases.

6. In human beings, the sound is produced by the voice box or the larynx.

7. Voice box is located at the upper end of the windpipe.

8.The eardrum senses the vibration of sound and sends the signal to the brain. This process is called hearing.

9.A vibration has three important characteristics – frequency, amplitude and time period.

10. Frequency is defined as the number of vibrations made by a vibrating body in one second. Its unit is hertz (Hz).

11. Amplitude is defined as the maximum extent to which a vibrating body can vibrate.

12. Time period is defined as the time taken by a vibrating body for one complete vibration.

13. Loudness is the characteristic of sound that enables us to distinguish a loud sound from low sound.

14. Pitch is a characteristic of sound that enables us to distinguish a shrill sound from the grave (hoarse) sound.

15. The term quality is defined as the characteristic of sound by virtue of which we can easily differentiate the two souand of same pitch. 

Important Terms

Amplitude: is defined as the maximum extent to which a vibrating body can vibrate.

Audible: The type of sounds which we are able to hear are called audible sounds.

Eardrum: Eardrum is a thin membrane through which the sound waves passed.

Hertz: The frequency is expressed in hertz (Hz).

Larynx: Larynx is the organ which produces sound in the human being. It is also called voice box.

Loudness: Is the characteristic of sound that enables us to distinguish a loud sound from low sound.

Noise: The sound which are unpleasant to hear are termed as noise

Oscillation: The to and fro motion of the vibrating particles about its mean position is called oscillation.

Pitch: The characteristic of sound by which we distinguish between different sounds of the same loudness is known as pitch.

Shrillness: The property of sound that depends upon frequency of vibrating object is known as shrillness.

Time period: The time taken by the bob of the pendulum to complete one oscillation, is called its time period.

Ultrasonic sound: The sound which have frequencies greater than 20,000 Hz is called ultrasonic sound.

Vibration: The movement of a body from one extreme position to the other is termed as vibration.

Voice box: It is that part by which sound is produced in humans

Oscillation: The to and fro motion of the vibrating particles about its mean position is called oscillation.

Pitch: The characteristic of sound by which we distinguish between different sounds of the same loudness is known as pitch.

Shrillness: The property of sound that depends upon frequency of vibrating object is known as shrillness.

Time period: The time taken by the bob of the pendulum to complete one oscillation, is called its time period.

Ultrasonic sound: The sound which have frequencies greater than 20,000 Hz is called ultrasonic sound.

Vibration: The movement of a body from one extreme position to the other is termed as vibration.

Voice box: It is that part by which sound is produced in humans.

Windpipe: The pipe which connects the larynx with the lungs is called windpipe

Chemistry class 10 chapter 2 part 2

                      CHEMISTRY-X

                           Chapter-2

GAS LAWS AND MOLE CONCEPT

Relationship between Volume and Temperature

Experiment: 1

Materials : Balloon, water, bottle, vessel, flame.

Procedure : Fix the balloon at the mouth of the bottle. Allow the bottle to heat in a water bath.

Observation : Volume of the balloon increases. When temperature is increased, the kinetic energy of the molecules also increases. Hence the volume of gas molecules expand.

 Charles’ Law: At constant pressure, the volume of a definite mass of a gas is directly proportional to the temperature in Kelvin scale. If V is volume and T is temperature, Then V/T will be a constant.

V ∝ T (mass& pressure are constant )

V = a constant × T

V/T = a constant

  Scale: Kelvin (K) is the SI unit of temperature. Other units are degree Celsius& degree Fahrenheit. 

Experiment: 2 (to prove charles’ law)

Materials : Dry bottle with rubber lid, An empty refill tube of a ball pen without nib, Ink, Warm water, ice water.

Procedure : Fix the empty refill through the rubber lid. Insert a drop of ink into the

 lower end of the tube and close the bottle with the lid. Dip this arrangement in 

 warm water. Then keep this arrangement in ice water.

Observation : The ink drop rises when the bottle placed in warm water. The ink drop moves in downward direction when the bottle kept in ice water

Conclusion : Charles’ Law: At constant pressure the volume of a definite mass of a gas  is directly proportional to its temperature on Kelvin scale.

Complete the table

Situations related to Charles’ Law 

1. The size of the inflated balloons used for celebrations increases and burst in sun.

 2.The tyres of the vehicles parked in sun have more chance to puncture.

Relationship between Volume and Number of Molecules.

Experiment

Material : Balloon

Procedure : Inflate the balloon. Allow the air to flow out from the balloon slowly.

Observation : The volume of the balloon increases when the balloon is inflated. Because the number of air molecules increases. When the air is removed from the balloon its volume decreases.

Conclusion :

 Avogadro’s Law: At constant temperature and pressure the volume of a gas is directly proportional to number of molecules.

V∝n

Situations related to Avogadro’s Law.

 1.Inflating of balloon. 

 2.The filling of air in the tyres of vehicles.

3.Filling of air in air bed.

 

 

 

Chemistry 10 chapter 2 part 1

 CHEMISTRY-X

Chapter-2

GAS LAWS AND MOLE CONCEPT

Difference between Solid, Liquid and Gas molecules

CHARACTERISTICS OF GASES

 Each gas contains numerous minute molecules.

 When compared to the total volume of a gas, the real volume of molecules is very less.

 The molecules of a gas are in a state of rapid motion in all directions.

 During the random motion of gas molecules, they collide with each other and also collide with the 

walls of the container in which it is kept.

 The collision of the gas molecules with the wall of the container, creates the pressure of the gas.

 As the collisions of molecules are perfectly elastic in nature, there is no loss of energy.

 There is no attraction between gas molecules and with the wall of the container.

Q)Complete the Table (ON THE BASIS OF ABOVE PROPERTIES)

VOLUME OF A GAS AND PRESSURE

 Volume of a gas is the volume of the container which it occupies.

 During the random motion of gas molecules, they collide with each other and also collide with the walls of the container in which it is kept. This collision with the walls accounts for the pressure of a gas.

 Force exerted per unit area is called pressure.

 Force on unit area(pressure)= 

  Total force exerted on the surface/surface area

         Unit - atomsphere (atm)   

                        

Temperature of a gas

1. Which is the energy gained due to the movement of the molecules?

 Kinetic energy

2. When a gas is heated, temperature is increased. What happens to the movement of molecules if the temperature of the gas is increased?

  When the freedom of movement of gas molecules increases the energy of the molecules also increases

Temperature 

 Temperature  is the average kinetic energy of molecules in a substance.

Unit- kelvin (K)

Activity 1

 Pull the piston of a syringe backwards. Press the piston after closing the nozzle of the syringe. What will happen to the volume of thesubstance

Observation: Volume of the balloon decreases.

Relationship between Volume and Pressure of a gas

Activity 2

 Definite mass of a gas is kept in a closed cylinder A. Suppose the gas is transferred to the other cylinder B without changing the Temperature. Is there any change in the number of molecules? What happens to the pressure when the volume is decreased?

 Observation: No change in number of molecules.

 When the pressure is increased the volume of gas decreases.

BOYLE'S LAW

 At a constant temperature, volume of a definite mass of gas is inversely proportional to its pressure. If p is pressure and v is volume then p×v is a constant.

V ∝1/p

V=a constant × 1/p

P × V = a constant

1. Find p×v

2.Which gas law is related to this.

3.what will be the volume of the gas if the pressure is changed to 2atm under the same conditions?

Q) The size of the air bubbles rising from the bottom of an aquarium increases. Can you explain the reason?

The pressure is very high in depth of water. This high pressure reduces the volume of the air bubbles. The size of the air bubbles increases as the pressure decreases when the bubbles move upwards.

Real life examples of BOYLE'S LAW

 1.Syringe

2. Human lungs 

3. Bicycles pump

4. Air bubbles on the surface of water