14 1 Properties of Gases A soccer ball

14. 1 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. Slide 1 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > Chemistry Temperature Matter Rates of Effusion and Effusion Pressure Gas Density Volume Moles Molar Mass Slide 2 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > Compressibility Why are gases easier to compress than solids or liquids are? Slide 3 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > 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. Slide 4 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > 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. Slide 5 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > Compressibility At room temperature, the distance between particles in an enclosed gas is about 10 times the diameter of a particle. Slide 6 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > Factors Affecting Gas Pressure What are three factors that affect gas pressure? • Amount of Gas • Volume • Temperature Slide 7 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > 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). Slide 8 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > 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. Slide 9 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > Heat 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 Slide 10 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > 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. Slide 11 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > Factors Affecting Gas Pressure If the gas pressure increases until it exceeds the strength of an enclosed, rigid container, the container will burst. Slide 12 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > Factors Affecting Gas Pressure Aerosol Spray Paint Slide 13 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > 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. Slide 14 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > Factors Affecting Gas Pressure When the volume of the container is halved, the pressure the gas exerts is doubled. Slide 15 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > 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. Slide 16 of 21 © Copyright Pearson Prentice Hall

14. 1 Properties of Gases > Factors Affecting Gas Pressure When the Kelvin temperature of the enclosed gas doubles, the pressure of the enclosed gas doubles. Slide 17 of 21 © Copyright Pearson Prentice Hall

14. 1 Section Quiz. Assess students’ understanding of the concepts in Section 14. 1. Continue to: -or- Launch: Section Quiz Slide 18 of 21 © Copyright Pearson Prentice Hall

14. 1 Section Quiz. 1. Compared to liquids and solids, gases are easily compressed because the particles in a gas a. attract each other. b. are spaced relatively far apart. c. are very small. d. repel each other. Slide 19 of 21 © Copyright Pearson Prentice Hall

14. 1 Section Quiz. 2. Gas pressure is affected by a. temperature, volume, and the amount of the gas. b. temperature, volume, and the molar mass of the gas. c. phase diagram, volume, and the size of the container. d. temperature, phase diagram, and the mass Slide of the gas container. 20 of 21 © Copyright Pearson Prentice Hall

14. 1 Section Quiz. 3. For gases, the SI units for volume (V), pressure (P), and temperature (T) are, respectively, a. liters, kilopascals, and °C. b. liters, kilopascals, and kelvins. c. cm 3, kilopascals, and kelvins. d. liters, atmospheres, and °C. Slide 21 of 21 © Copyright Pearson Prentice Hall

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. Slide 22 of 21 © Copyright Pearson Prentice Hall

Boyle’s Law: Pressure and Volume How are the pressure, volume, and temperature of a gas related? Slide 23 of 21 © Copyright Pearson Prentice Hall

Boyle’s Law: Pressure and Volume If the temperature is constant, as the pressure of a gas increases, the volume decreases. Slide 24 of 21 © Copyright Pearson Prentice Hall

Boyle’s Law: Pressure and Volume a. Boyle’s law states that for a given mass of gas at constant temperature, the volume of the gas varies inversely with pressure. Slide 25 of 21 © Copyright Pearson Prentice Hall

Boyle’s Law: Pressure and Volume Slide 26 of 21 © Copyright Pearson Prentice Hall

Boyle’s Law: Pressure and Volume Simulation 15 Examine the relationship between gas, volume and pressure. Slide 27 of 21 © Copyright Pearson Prentice Hall

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for Sample Problem 14. 1 Problem Solving 14. 8 Solve Problem 8 with the help of an interactive guided tutorial. © Copyright Pearson Prentice Hall Slide 32 of 21