Universal Gas Law

Gas Laws

Section 3.2

Breathing Exercise

Put your hand in front of your chest.

Inhale deep.

Exhale deep.

Describe your experience.

Open Ended

Define PRESSURE.

Multiple Choice

All of the following are units of pressure except one. Which is it?

• $$\frac{N}{m^2}$$  
  

• Pascal

• mm Hg

• kg

Pressure

• Force exerted by molecules in a given area.

• Units:  $\frac{N}{m^2}$  or Pa or mm Hg or atm or bar

• Collisions between particles of a gas and the walls of the container cause the pressure in a closed container of a gas.

Factors Affecting Gas Pressure (in an enclosed container)

• Temperature

• Volume

• Number of particles

A. Temperature

• Definition: The measure of the average kinetic energy of molecules of a substance.

• Raising the temperature of a gas will increase its pressure if the volume of the gas and the number of particles are CONSTANT.

Multiple Choice

What will happen if you to the pressure of the molecules in an enclosed container if you heat it?

• It will increase.

• It will decrease.

• It will remain the same.

• Heat has no effect on pressure.

B. Volume

• Definition: Amount of matter in a substance.

• Reducing the volume of a gas increases its pressure if the temperature of the gas and the number of particles are CONSTANT.

Multiple Choice

As volume increases, the pressure decreases at constant temperature and number of particles. What is the relationship between volume and pressure?

• directly proportional

• inversely proportional

• no relationship

• direct square relationship

Multiple Choice

As volume increases, the pressure decreases at constant temperature and number of particles. What is the relationship between volume and pressure?

• directly proportional

• inversely proportional

• no relationship

• direct square relationship

Open Ended

Will the pressure INCREASE or DECREASE if you add more particles (contant temperature and volume)?