Today’s lesson (Supplement only)

1. 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.

2. Pressure in a gas What is origin of the pressure of a gas? Volunteers please!

3. 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

4. Pressure and Volume at constant temp? http://phet.colorado.edu/en/simulation/gas-properties

5. pV = constant • p1V1 = p2V2 (at constant temp) This is only true for a constant mass of gas at constant temperature.

6. 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)?

7. 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 = ?

8. 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

9. 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

10. pV = constant This is only true for a constant mass of gas at constant temperature. Can you answer the questions that Mr Porter is giving you? p1V1 = p2V2 (at constant temp)