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

Rates of Effusion and Effusion Chemistry Matter Gas Temperature Pressure Volume Moles Molar Mass Density Rates of Effusion and Effusion

Compressibility Compressibility Why are gases easier to compress than solids or liquids are?

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. A crash dummy can be used to test the effectiveness of an air bag. Because gases can be compressed, the air bag absorbs some of the energy from the impact of a collision. Air bags work best when combined with seat belts.

Under pressure, the particles in a gas are forced closer together. Compressibility Gases are easily compressed because of the space between the particles in a gas. The distance between particles in a gas 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. There are only a few nitrogen and oxygen molecules in this model of air. At room temperature, the distance between molecules in a container of air at standard pressure is about 10 times the diameter of a molecule.

Factors Affecting Gas Pressure What are the three factors that affect gas pressure? Amount of Gas Volume Temperature

Factors Affecting Gas Pressure Four variables are generally used to describe a gas. The variables and their common units are pressure (P) in kilopascals volume (V) in liters temperature (T) in kelvins the number of moles (n).

Factors Affecting Gas Pressure Amount of Gas You can use kinetic theory 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.

Heat Temperature Pressure Volume Energy transferred due to differences in temperature Temperature Measure of the average kinetic energy of particles composing a material Pressure Force per unit area Volume The amount of space a material occupies

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. If you increase the number of particles it will increase the number of collisions, which is why the gas pressure increases. The volume of this air-filled raft is much larger than its volume before it was inflated. Using a pump to force air into a raft increases the pressure of the air inside the raft. The increased pressure causes the raft to inflate to its intended size.

Factors Affecting Gas Pressure If the gas pressure increases until it exceeds the strength of an enclosed, rigid container, the container will burst. When a gas is pumped into a closed rigid container, the pressure increases as more particles are added. If the number of particles is doubled, the pressure will double. Predicting What would happen to the pressure in the container if the number of particles were tripled? If the number of particles were cut in half?

Factors Affecting Gas Pressure Aerosol Spray Paint The pressure of the gas inside a new can of spray paint is greater than the air pressure outside the can. When gas rushes though an opening in the top of the can, it propels, or forces, paint out of the can. As the can is used, the pressure of the propellant decreases. Relating Cause and Effect What happens when the pressure of the propellant equals the air pressure outside the can?

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.

Factors Affecting Gas Pressure When the volume of the container is halved, the pressure the gas exerts is doubled. A piston can be used to force a gas in a cylinder into a smaller volume. When the volume is decreased, the pressure the gas exerts is increased. Interpreting Diagrams What happens to the gas pressure when the volume is reduced from 1 L to 0.5 L?

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 Pressure When the Kelvin temperature of the enclosed gas doubles, the pressure of the enclosed gas doubles. An increase in temperature causes an increase in the pressure of an enclosed gas. The container can explode if there is too great an increase in the pressure.

14.1 Section Quiz. 14.1.

14.1 Section Quiz. 1. Compared to liquids and solids, gases are easily compressed because the particles in a gas attract each other. are spaced relatively far apart. are very small. repel each other.

14.1 Section Quiz. 2. Gas pressure is affected by temperature, volume, and the amount of the gas. temperature, volume, and the molar mass of the gas. phase diagram, volume, and the size of the container. temperature, phase diagram, and the mass of the gas container.

14.1 Section Quiz. 3. For gases, the SI units for volume (V), pressure (P), and temperature (T) are, respectively, liters, kilopascals, and °C. liters, kilopascals, and kelvins. cm3, kilopascals, and kelvins. liters, atmospheres, and °C.

The Gas Laws This hot air balloon was designed to carry a passenger around the world. You will study some laws that will allow you to predict gas behavior under specific conditions, such as in a hot air balloon.

Boyle’s Law: Pressure and Volume How are the pressure, volume, and temperature of a gas related?

Boyle’s Law: Pressure and Volume If the temperature is constant, as the pressure of a gas increases, the volume decreases.

Boyle’s Law: Pressure and Volume Boyle’s law states that for a given mass of gas at constant temperature, the volume of the gas varies inversely with pressure.

Boyle’s Law: Pressure and Volume The pressure of a gas changes as the volume changes. INTERPRETING GRAPHS a. Observing When the volume is 2.0 L, what is the pressure? b. Predicting What would the pressure be if the volume were increased to 3.0 L? c. Drawing Conclusions Based on the shape of the graph, describe the general pressure-volume relationship.

Boyle’s Law: Pressure and Volume Simulation 15 Examine the relationship between gas, volume and pressure.

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for Sample Problem 14.1 Problem Solving 14.8 Solve Problem 8 with the help of an interactive guided tutorial.