Today’s lesson (Supplement only)

• Relate the change in volume of a gas to change in pressure applied to the gas at constant temperature and use the equation pV = constant at constant temperature.

Pressure in a gas

What is origin of the pressure of a gas?

Volunteers please!

Pressure in a gas

Collisions of the gas particles with the side of a container give rise to a force, which averaged of billions of collisions per second macroscopically is measured as the pressure of the gas

Pressure and Volume at constant temp?

http://phet.colorado.edu/en/simulation/gas-properties

pV = constant

• p1V1 = p2V2 (at constant temp)

This is only true for a constant mass of gas at constant temperature.

Example Question

• A packet of crisps has a volume of 200 cm3 at sea leveL (PRESSURE = 100 KPa). What volume will the packet have on the summit of Mount Everest (Pressure = 30 kPa)?

Example Question• A packet of crisps has a volume of 200 cm3 at sea leveL

(PRESSURE = 100 KPa). What volume will the packet have on the summit of Mount Everest (Pressure = 30 kPa)?

• P1 = 100 kPa, V1 = 200 cm3

• P2 = 30 kPa, V2 = ?

Example Question• A packet of crisps has a volume of 200 cm3 at sea leveL

(PRESSURE = 100 KPa). What volume will the packet have on the summit of Mount Everest (Pressure = 30 kPa)?

• P1 = 100 kPa, V1 = 200 cm3

• P2 = 30 kPa, V2 = ?

• P1 V1 = P2 V2 100x200 = 30V2

Example Question• A packet of crisps has a volume of 200 cm3 at sea leveL (PRESSURE

= 100 KPa). What volume will the packet have on the summit of Mount Everest (Pressure = 30 kPa)?

• P1 = 100 kPa, V1 = 200 cm3

• P2 = 30 kPa, V2 = ?

• P1 V1 = P2 V2 100x200 = 30V2

• 20000 = 30V2

• V2 = 20000/30 = 666 cm3

pV = constant

• p1V1 = p2V2 (at constant temp)

Can you answer the

questions that Mr Porter is giving you?

This is only true for a constant mass of gas at constant temperature.