Ideal Gases

Question 1

What are the assumptions made in the kinetic model?

Answer 1

1. The gas contains a very large number of molecules/atoms moving in random directions at random speeds.
   2.The atoms/molecules occupy a negligible volume compared with the volume of the gas.
2. The collisions of atoms/molecules and the container walls are perfectly elastic.
3. The time of collisions between atoms/molecules are negligible compared to the time between collisions.
4. Electrostatic forces between atoms or molecules are negligible, except during collisions.

Question 2

Using the assumption made in the kinetic model, how can you explain how the atoms/molecules in an ideal gas cause pressure?

Answer 2

The atoms or molecules in a gas are always moving and when they collide with walls of a container the container exerts a force on them changing their momentum as they bounce of the wall.
When a single atom collides with the container wall elastically. The total change in momentum is -2mu as velocity changes from +u to -u.
Then using F = change in momentum over change in time.
F is force on the atom and time is the time between the collisions.

A large number of atoms/molecules collide randomly with the walls of the container. If the total force they exert on the walls is F then the pressure they exert on the wall is give by P= F/A
Where A is the cross sectional area of the wall.

Question 3

What is Boyles Law?

Answer 3

The pressure of an ideal gas is inversely proportional to its volume, provided that the mass of gas and temperature do not vary.

Question 4

Explain the term Absolute Zero

Answer 4

The temperature at which internal energy is at a minimum. Temperature is -273 degrees or 0K. Lowest possible temperature of a substance.