© copyright pearson prentice hall slide 1 of 21 14.1 properties of gases a soccer ball properly...

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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.


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Properties of Gases >14.1


Properties of Gases >

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14.1 Compressibility

Compressibility

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

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Properties of Gases >14.1 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.

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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.

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


Properties of Gases >

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14.1 Factors Affecting Gas Pressure

Factors Affecting Gas Pressure

What are the three factors that affect gas pressure?

•Amount of Gas

•Volume

•Temperature

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Properties of Gases >14.1 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).

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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.

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Properties of Gases >14.1

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

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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.


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If the gas pressure increases until it exceeds the strength of an enclosed, rigid container, the container will burst.


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Aerosol Spray Paint

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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.


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

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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.


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When the Kelvin temperature of the enclosed gas doubles, the pressure of the enclosed gas doubles.


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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

14.1 Section Quiz.

14.1.


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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.


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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 of the gas container.


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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. cm3, kilopascals, and kelvins.

d. liters, atmospheres, and °C.


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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.


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Boyle’s Law: Pressure and Volume


How are the pressure, volume, and temperature of a gas related?


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If the temperature is constant, as the pressure of a gas increases, the volume decreases.


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


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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.

© copyright pearson prentice hall slide 1 of 21 14.1 properties of gases a soccer ball properly...

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