Post on 02-Jan-2016
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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
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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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Properties of Gases >14.1 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.
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Properties of Gases >14.1 Compressibility
At room temperature, the distance between particles in an enclosed gas is about 10 times the diameter of a particle.
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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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Properties of Gases >14.1 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.
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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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Properties of Gases >14.1 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.
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Properties of Gases >14.1 Factors Affecting Gas Pressure
If the gas pressure increases until it exceeds the strength of an enclosed, rigid container, the container will burst.
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Properties of Gases >14.1 Factors Affecting Gas Pressure
Aerosol Spray Paint
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Properties of Gases >14.1 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.
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Properties of Gases >14.1 Factors Affecting Gas Pressure
When the volume of the container is halved, the pressure the gas exerts is doubled.
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Properties of Gases >14.1 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.
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Properties of Gases >14.1 Factors Affecting Gas Pressure
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
Boyle’s Law: Pressure and Volume
How are the pressure, volume, and temperature of a gas related?
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Boyle’s Law: Pressure and Volume
If the temperature is constant, as the pressure of a gas increases, the volume decreases.
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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.
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Boyle’s Law: Pressure and Volume
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Boyle’s Law: Pressure and Volume
Simulation 15
Examine the relationship between gas, volume and pressure.
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14.1
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14.1
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14.1
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14.1
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for Sample Problem 14.1
Problem Solving 14.8
Solve Problem 8 with the help of an interactive guided tutorial.