Drill Quiz

C3H8 + 5O2 3 CO2 + 4H2O

If 65.0g of C3H8 are burned,… of CO2 at STP will be produced.

Objective

Swbat: Explore the different properties of gas

pressure in order to identify the factors that affect it.

SAT Enrichment

C3H8 + 5O2 3 CO2 + 4H2O If 106g of CO2 were produced from burning

C3H8,…of water would also be produced.

a. 32.5 gramsb. 57.8 gramsc. 61.0 gramsd. 79.5 gramse. 141 grams

Demonstration Pour out the Fire

Questions: 1. What caused the flame to go out? A gas was being poured onto the flames.2. Why was a cylinder needed? To force the gas to move downward to the flame.3. What gas was produced by the flame? CO24. What are some properties of the gas that are different from

the solid and liquid used in the demonstration? The gas is not visible, it escapes into the air easily, etc.

Properties of Gases

What makes a Gas a Gas?

Properties of Gases• In organized soccer, a ball that

is properly inflated will rebound faster and travel farther than a ball that is under-inflated. If the pressure is too high, the ball may burst when it is kicked. You will study variables that affect the pressure of a gas.

Compressibility

Compressibility is a measure of how much the volume of matter decreases under pressure.

When a person collides with an inflated airbag, the compression of the gas absorbs the energy of the impact.

Compressibility

Gases are easily compressed because of the space between the particles in a gas. The distance is much greater than the

distance between particles in a liquid or solid.

Under pressure, the particles in a gas are forced closer together.

Compressibility

At room temperature, the distance between particles in an enclosed gas is about 10 times the diameter of a particle.

Factors Affecting Gas Pressure

Four variables are generally used to describe a gas. The variables and their common units are pressure (P) in kilopascals (kPa) volume (V) in liters (L) temperature (T) in Kelvins (K) number of moles (n) in moles (mol)

Factors Affecting Gas Pressure

Amount of Gas

Kinetic theory can be used to predict and explain how gases will respond to a change of conditions.

If you inflate an air raft, for example, the pressure inside the raft will increase.

Factors Affecting Gas Pressure

Collisions of particles with the inside walls of the raft result in the pressure that is exerted by the enclosed gas. Increasing the number of particles increases

the number of collisions, which is why the gas pressure increases.

Factors Affecting Gas Pressure If the gas pressure increases until it exceeds

the strength of an enclosed, rigid container, the container will burst.

Factors Affecting Gas Pressure

Aerosol Spray Paint

Factors Affecting Gas Pressure Volume

You can raise the pressure exerted by a contained gas by reducing its volume.

The more a gas is compressed, the greater is the pressure that the gas exerts inside the container.

When the volume of the container is halved, the pressure the gas exerts is doubled.

Factors Affecting Gas Pressure Temperature

An increase in the temperature of an enclosed gas causes an increase in its pressure.

As a gas is heated, the average kinetic energy of the particles in the gas increases.

Faster-moving particles strike the walls of their container with more energy.

Factors Affecting Gas PressureWhen the Kelvin temperature of the enclosed gas doubles, the pressure of the enclosed gas doubles.

No Heat

Small amount of heat Double amount

Of heat

Class Activity

Investigating Phase change mini lab. How does the temperature of Lauric acid

change as it cools?

30 min

Extension

Organizing the States of Matter Using the words on the worksheet create a

concept map of the states of matter. One has been started for you on the back of

the worksheet.

Summary

1. Did we accomplish the objective? Explain.2. Identify the four variables that affect gas

pressure.3. Compare and contrast the effect on gas

pressure when temperature and volume are increased. Decreased.

4. Give an example of how gas pressure would be important for you to know during your everyday life.

Homework

“Fast Enough For You” wksheet.