When you inhale, the volume of your chest cavity increases, and air moves into your lungs. When you exhale, the volume of your chest cavity decreases, and air is pushed out of your lungs. Changes in the volume, the temperature, the pressure, and the

1

• When you inhale, the volume of your chest cavity
  increases, and air moves into your lungs. When
  you exhale, the volume of your chest cavity
  decreases, and air is pushed out of your lungs.
  Changes in the volume, the temperature, the
  pressure, and the number of particles have
  predictable effects on the behavior of a gas.

2
Pressure

• What causes gas pressure in a closed container?
• Pressure is the result of a force distributed
  over an area.

Collisions between particles of a gas and the
walls of the container cause the pressure in a
closed container of gas.
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Pressure

• A moving hockey puck exerts pressure on any
  object it hits. A layer of shatterproof glass
  protects spectators.
• The faster the puck is traveling, the greater the
  force of the puck on the glass. A greater force
  means more pressure.
• The smaller the area of impact is, the greater
  the pressure. If the edge of the puck hits the
  glass, it exerts more pressure than if the face
  of the puck hits the glass.

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Pressure

• The SI unit of pressure is derived from SI units
  for force and area.
• Force is measured in newtons (N).
• Area is measured in square meters (m2).
• The SI unit for pressure, the pascal (Pa), is
  shorthand for newtons per square meter.
• Scientists often express larger amounts of
  pressure in kilopascals. One kilopascal (kPa) is
  equal to 1000 pascals.

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Pressure

• The helium atoms in a balloon are constantly
  moving. There are more than 1022 helium atoms in
  a small balloon.
• When many particles collide with the walls of a
  container at the same time, they produce a
  measurable pressure.
• The more frequent the collisions, the greater the
  pressure is.
• The speed of the particles and their mass also
  affect the pressure.

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Factors That Affect Gas Pressure

• What factors affect gas pressure?

Factors that affect the pressure of an enclosed
gas are its temperature, its volume, and the
number of its particles.
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Factors That Affect Gas Pressure

• Temperature

Raising the temperature of a gas will increase
its pressure if the volume of the gas and the
number of particles are constant.
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Factors That Affect Gas Pressure

• The firefighter is using a pressure gauge to
  check the air pressure in a tire on a firetruck.
• If he checks the tire pressure again after a long
  drive on a highway, he will find that the
  pressure has increased.

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Factors That Affect Gas Pressure

• The motion of tires on the highway heats the
  tires and increases tire pressure.
• As the temperature rises, the average kinetic
  energy of the particles in the air increases.
• With increased kinetic energy, the particles move
  faster and collide more often with the inner
  walls of the tires.
• Faster-moving particles hit the walls with
  greater force.
• More collisions and increased force cause the
  pressure of the air in the tires to rise.

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Factors That Affect Gas Pressure

• Volume

Reducing the volume of a gas increases its
pressure if the temperature of the gas and the
number of particles are constant.
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Factors That Affect Gas Pressure

• Twist the cap onto a plastic bottle and then
  squeeze it. What happens?
• The volume of the plastic bottle begins to
  decrease.
• As the volume decreases, the particles of trapped
  air collide more often with the walls of the
  bottle.
• The pressure in the bottle increases.

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Factors That Affect Gas Pressure

• Movement of a muscle called the diaphragm changes
  the volume of your chest cavity.
• The volume increases when you inhale. The
  pressure decreases and air flows to your lungs.
• The volume decreases when you exhale. The
  pressure increases and air flows from your lungs.

Inhaling
Exhaling
Diaphragm contracts. Rib cage is lifted up and
out.
Diaphragm relaxes. Rib cage moves down and in.
Lungs
Rib Cage
Diaphragm
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Factors That Affect Gas Pressure

• Number of Particles

Increasing the number of particles will increase
the pressure of a gas if the temperature and the
volume are constant. The more particles there
are in the same volume, the greater the number of
collisions and the greater the pressure.
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Charless Law

• French physicist Jacques Charles collected data
  on the relationship between the temperature and
  volume of gases. The graph of the data showed a
  direct relationship between the volume of a gas
  and the temperature of the gas.

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Charless Law

• Charles extended the graph beyond the measured
  data to find the temperature that would produce a
  volume of 0 L.
• The temperature at the point where the line
  crossed the x-axis was 273.15C.

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Charless Law

• Charles extended the graph beyond the measured
  data to find the temperature that would produce a
  volume of 0 L.
• The temperature at the point where the line
  crossed the x-axis was 273.15C.

17
Charless Law

• Charles extended the graph beyond the measured
  data to find the temperature that would produce a
  volume of 0 L.
• The temperature at the point where the line
  crossed the x-axis was 273.15C.

18
Charless Law

• Charles extended the graph beyond the measured
  data to find the temperature that would produce a
  volume of 0 L.
• The temperature at the point where the line
  crossed the x-axis was 273.15C.

19
Charless Law

• Charles extended the graph beyond the measured
  data to find the temperature that would produce a
  volume of 0 L.
• The temperature at the point where the line
  crossed the x-axis was 273.15C.

20
Charless Law

• Charles extended the graph beyond the measured
  data to find the temperature that would produce a
  volume of 0 L.
• The temperature at the point where the line
  crossed the x-axis was 273.15C.

21
Charless Law

• Charles extended the graph beyond the measured
  data to find the temperature that would produce a
  volume of 0 L.
• The temperature at the point where the line
  crossed the x-axis was 273.15C.

22
Charless Law

• Charles extended the graph beyond the measured
  data to find the temperature that would produce a
  volume of 0 L.
• The temperature at the point where the line
  crossed the x-axis was 273.15C.

23
Charless Law

• Charles extended the graph beyond the measured
  data to find the temperature that would produce a
  volume of 0 L.
• The temperature at the point where the line
  crossed the x-axis was 273.15C.

24
Charless Law

• This temperature is equal to 0 K on the Kelvin
  temperature scale.
• A temperature of 0 K is called absolute zero.

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Charless Law

• Charless law states that the volume of a gas is
  directly proportional to its temperature in
  kelvins if the pressure and the number of
  particles of the gas are constant.
• T1 and V1 represent the temperature and volume of
  a gas before a change occurs. T2 and V2 represent
  the temperature and volume after a change occurs.

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Boyles Law

• Robert Boyle described the relationship between
  the pressure and volume of a gas. The graph shows
  an inverse relationship between the volume of a
  gas and the pressure of the gas.

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Boyles Law

• Robert Boyle described the relationship between
  the pressure and volume of a gas. The graph shows
  an inverse relationship between the volume of a
  gas and the pressure of the gas.

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Boyles Law

• Robert Boyle described the relationship between
  the pressure and volume of a gas. The graph shows
  an inverse relationship between the volume of a
  gas and the pressure of the gas.

29
Boyles Law

• Robert Boyle described the relationship between
  the pressure and volume of a gas. The graph shows
  an inverse relationship between the volume of a
  gas and the pressure of the gas.

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Boyles Law

• Boyles law states that the volume of a gas is
  inversely proportional to its pressure if the
  temperature and the number of particles are
  constant.
• P1 and V1 represent the pressure and volume of a
  gas before a change occurs. P2 and V2 represent
  the pressure and volume of a gas after a change
  occurs.

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The Combined Gas Law

• The relationships described by Boyles law and
  Charless law can be described by a single law.
  The combined gas law describes the relationship
  among the temperature, volume, and pressure of a
  gas when the number of particles is constant.

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The Combined Gas Law

• The Combined Gas Law
• A cylinder that contains air at a pressure of 100
  kPa has a volume of 0.75 L. The pressure is
  increased to 300 kPa. The temperature does not
  change. Find the new volume of air.

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The Combined Gas Law

• Read and Understand
• What information are you given?

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The Combined Gas Law

• Read and Understand
• What information are you given?
• P1 100 kPa P2 300 kPa V1 0.75 L

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The Combined Gas Law

• Plan and Solve
• What unknown are you trying to calculate?
• What expression can you use?

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The Combined Gas Law

• Plan and Solve
• What unknown are you trying to calculate?
• What expression can you use?

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The Combined Gas Law

• Plan and Solve
• Cancel out the variable that does not change and
  rearrange the expression to solve for V2.
• Replace each variable with its known value.

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The Combined Gas Law

• Plan and Solve
• Cancel out the variable that does not change and
  rearrange the expression to solve for V2.
• Replace each variable with its known value.

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The Combined Gas Law

• Look Back and Check
• Is your answer reasonable?

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The Combined Gas Law

• Look Back and Check
• Is your answer reasonable?
• Volume should decrease as pressure increases. The
  pressure tripled from 100 kPa to 300 kPa. The
  answer, 0.25 L, is one third the original volume,
  0.75 L.

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The Combined Gas Law

• 1. A gas has a volume of 5.0 L at a pressure of
  50 kPa. What happens to the volume when the
  pressure is increased to 125 kPa? The temperature
  does not change.

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The Combined Gas Law

• 2. Gas stored in a tank at 273 K has a pressure
  of 388 kPa. The safe limit for the pressure is
  825 kPa. At what temperature will the gas reach
  this pressure?

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The Combined Gas Law

• 3. At 10ºC, the gas in a cylinder has a volume of
  0.250 L. The gas is allowed to expand to 0.285 L.
  What must the final temperature be for the
  pressure to remain constant? (Hint Convert from
  degrees Celsius to kelvins using the expression
  ºC 273 K.)

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The Combined Gas Law

• Balloons like this one are used by scientists to
  gather data about Earths atmosphere. The balloon
  is filled with hydrogen or helium. It carries a
  package of weather instruments up into the
  atmosphere.

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The Combined Gas Law

• The gas laws explain the behavior of the gas in
  the balloon.

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Assessment Questions

• What causes the pressure to increase if more gas
  particles are added to a closed container?
• an increase in the number of collisions between
  the gas and the container walls
• a decrease in the volume of the container
• a decrease in the size of each particle as the
  number of particles increases
• an increase in the number of collisions between
  air particles and the outside of the container

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Assessment Questions

• What causes the pressure to increase if more gas
  particles are added to a closed container?
• an increase in the number of collisions between
  the gas and the container walls
• a decrease in the volume of the container
• a decrease in the size of each particle as the
  number of particles increases
• an increase in the number of collisions between
  air particles and the outside of the
  containerANS A

48
Assessment Questions

• When first blown up, a balloon is firm because of
  the air pressure inside it. However, after time,
  the balloon becomes soft as the air pressure
  inside drops. What could have caused the air
  pressure to decrease?
• increase in air temperature
• decrease in the balloon's volume
• decrease in the number of air particles as they
  leaked out of the balloon
• a chemical reaction between the air particles and
  the balloon

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Assessment Questions

• When first blown up, a balloon is firm because of
  the air pressure inside it. However, after time,
  the balloon becomes soft as the air pressure
  inside drops. What could have caused the air
  pressure to decrease?
• increase in air temperature
• decrease in the balloon's volume
• decrease in the number of air particles as they
  leaked out of the balloon
• a chemical reaction between the air particles and
  the balloon
• ANS C

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Assessment Questions

• A gas has a volume of 15 L, a temperature of
  300 K, and an unknown initial pressure. Then, the
  gas expands to 30 L, remains at 300 K, and has a
  pressure of 300 kPa. What was the initial
  pressure of the gas?
• 150 kPa
• 600 kPa
• 330 kPa
• 570 kPa

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Assessment Questions

• A gas has a volume of 15 L, a temperature of
  300 K, and an unknown initial pressure. Then, the
  gas expands to 30 L, remains at 300 K, and has a
  pressure of 300 kPa. What was the initial
  pressure of the gas?
• 150 kPa
• 600 kPa
• 330 kPa
• 570 kPaANS B

52
Assessment Questions

• According to Charless law, the relationship
  between the temperature and the volume of a gas
  is
• direct.
• inverse.
• exponential.
• inverse square.

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Assessment Questions

• According to Charless law, the relationship
  between the temperature and the volume of a gas
  is
• direct.
• inverse.
• exponential.
• inverse square.ANS A

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Assessment Questions

• When the temperature of the gas in closed
  container is increased, the pressure
  increases.TrueFalse

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Assessment Questions

• When the temperature of the gas in closed
  container is increased, the pressure
  increases.TrueFalse
• ANS T