Kinetcic theory of gases

Question 1

What is the kentic theory of gases?

Answer 1

• Molecules in a gas are in constant random motion at high speeds
• Random motion means that the molecules are travelling in no specific path and undergo sudden changes in their motion if they collide:
• With the walls of its container
• With other molecules

The random motion of tiny particles in a fluid is known as Brownian motion

Question 2

What does Brownian motion provide evidence for?

Answer 2

That air is made of small particles

This is because when larger particles, such as smoke particles or pollen, are observed floating in the air:
The larger particles move with random motion
This is a result of the larger particles colliding with smaller particles that are invisible to the naked eye

Question 3

What is pressure in gases?

Answer 3

When gases fill their container the pressure is teh force per unit area

Question 4

What happens when a gas is contained in a container?

Answer 4

• As the gas particles move about randomly they collide with the walls of their containers
• These collisions produce a net force at right angles to the wall of the gas container (or any surface)
• Therefore, a gas at high pressure has more frequent collisions with the container walls and a greater force

The higher the pressure, the higher the force exerted per unit area

It is possible for someone to experience this force by closing their mouth and forcing air into their cheeks
The strain on the cheeks is due to the force of the gas particles pushing at right angles to the cheeks

Question 5

What is teh equation for pressure?

Answer 5

Pressure= Force/Area

Pressure (Pa)
Force (N)
Area (m^2)

Another equation that may be usful in questions is fore of 1 molecule x number of molecules
Both equations may be needed in the same question dependig on what is asked.