Ideal Gas

Air is contained in a volume with a piston.The piston is pushed down to half of the original height while the temperature is held constant by a surrounding

ice bath. By which factor does the force of the air against the piston change?

a) 1/2

b) 1

c) 2

d) 4

150 K

Air at 150 K is contained in a can with a lose piston. The temperature is increased to 300 K. Where will the

piston be?

a) At ½ height

b) At twice the height

c) No change

d) No change, but the pressure will be half

An Air compressor increases the pressure from 1 atm to 5 atm. Enough time is given for the temperature to

adjust back to the surrounding temperature.If the density of the outside air is 1.2 kg/m3, what is the

density of air inside of the air compressor?

6 kg/m3

The tank holds a volume of 50 L.By how much does the weight of the tank change, if

the density is increased from 1.2 kg/m3 to 6 kg/m3?

Compare the density of dry air at a summer temperature of 30 C to the density of dry air at -20 C by finding the ratio of density summer/winter.

If the atmospheric pressure on a 15 C is equal to 1002 hPa, how much mass of air is contained in a room the size of the class room (20m by 20 m by 3 m)?

How much pressure will the weight of this air exert onto the floor of the room

(20m by 20 m by 3 m)?

How much mass of air is

located in an air column of

1 square meter cross

sectional area, in order to

cause normal atmospheric

pressure with its weight?

Constant density:

1.225 kg/m3

Constant pressure

1000 mbarNeeds a force equivalent to the weight of the air

1000 m

1000 mbar1000 m

100 mbar

Releasing a slice of 1/10 of mass on top

Density and pressure drop – why?

1000 mbar1000 m

100 mbar

Releasing another slice of 1/10 of mass

100 mbar

200 mbar

1000 mbar1000 m

Releasing a third slice of 1/10 of mass

100 mbar

200 mbar

100 mbar

200 mbar

300 mbar

1000 mbar1000 m

Releasing a 4th slice of 1/10 of mass100 mbar

200 mbar

300 mbar

100 mbar

400 mbar

Continuous atmosphere

2000 m800 mb80% above

0 m1000 mb100% above

5500 m500 mb50% below

12000 m200 mb80% below

The density of air

dry moist

Nitrogen replaced by water molecules:

M(nitrogen)=28 to M(water)=18

Which of these air parcels will have the lower density?