Chapter 15 - Ideal Gases

Question 1

What are the assumptions made about ideal gases?

Answer 1

• Gas contains very large number of atom/molecules moving in random directions and speeds.
• Atoms/molecules occupy negligible volume compared to the volume of gas.
• Collisions of atoms/molecules with each other and the wall is perfectly elastic.
• Electrostatic forces between atoms/molecules are negligible except during collisions.

Question 2

How is pressure created in a container?

Answer 2

• Momentum of atoms/molecule changes when they collide with wall.
• Newton II and III
• Pressure exerted by all atoms = total force/cross-sectional area.

Question 3

State Boyle’s Law.

Answer 3

Pressure is inversely proportional to volume.

Question 4

Investigating Boyle’s Law.

Answer 4

Gas in sealed tube (fixed mass).
Use pump to increase level of oil.
Pressure gauge measures the pressure.
Plot pressure against volume of gas.

Question 5

What is the relationship between pressure and temperature of an ideal gas?

Answer 5

They are directly proportional (when V and m are constant).

Question 6

Experiment to estimate absolute zero.

Answer 6

Dry air in flask, connected to pressure gauge.
Place in water bath and record increase in pressure when temperature is increased.

At absolute zero, particles are not moving.
Plot P against θ and extrapolate back to P=0.

Question 7

Internal energy in an ideal gas

Answer 7

Assume that electrostatic forces between atoms/molecules is negligible except during collisions.

Therefore all IE in an ideal gas is kinetic energy.