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