Chemistry

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Chemistry

• Gas Pressure

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Crush the Can Demo What Crushed the Can?

• A pop can containing a small amount of water is
  heated until the water boils.
• The can is then submerged in a pan of cold water
• Crunch the can is crushed

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Crush the Can Demo Energy Transfer
Q
Ek
Ei
Ech
Ek
Ei
Ech
Ek
Ei
Ech
Water
Water
Water in Can Before Heating
Water Boiling
Water in Can in Cold Water
Q
Liquid Water
Water Vapor (Gas)
Liquid Water
Q
- Q
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Crush the Can Demo Kinetic Theory of Matter
Particles in the Can
Water vapor condenses and collects at the bottom
of can. No particles occupy the remaining space
of the can
Water vapor particles fill volume of can pushing
air particles out
Particles of liquid water are close, but free to
flow. Gaseous air particle fill remaining volume
of can
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Crush the Can DemoAir Pressure
Gas particles in the air push down of the can.
At first this air pressure is balanced by the
air pressure inside the can. However, when the
water vapor condenses, the air pressure inside
the can is decreased dramatically.
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Crush the Can Demo Air Pressure Crushes the Can
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Pressure (P)

• The force of collisions on a certain area.
• Pressure Force Exerted / Area
• Variety of units psi, pascal, torr, mm of Hg,
  and atmospheres are some common examples.
• Pressure can be measured by pressure gages /
  sensors, barometers, or manometers.

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Atmospheric (Air) Pressure

• Standard pressure at sea level is 760mm of Hg, or
  101.3kPa.
• Atmospheric pressure varies with weather
  conditions and altitude.

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Measuring Pressure

• Describe what happen to the water level in the
  manometer when the containers pressure is less
  than atmospheric pressure. Label the area of
  high pressure and the area of low pressure.

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Measuring Pressure

• Describe what happened to the water level in the
  manometer when the containers pressure is
  increased above atmospheric pressure.

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Factors that Affect Gas Pressure

• Temperature of the Gas
• Volume of the Gas
• Amount (mass) of the Gas
• Altitude
• Weather Conditions

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Factors that Affect Gas Pressure Altitude and
Weather

• Altitude and weather are two environmental
  conditions that would be difficult to test in the
  classroom.
• To reduce the chance these factors might
  influence our results, we will conduct the
  investigation on the same day (same weather
  conditions) and at the same altitude.

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Factors that Affect Gas Pressure Mass (Amount
of Gas)

• Mass or the amount of gas present is also
  difficult to test in the lab.
• During our investigation, the amount of gas
  (mass) will be kept constant by sealing the
  system to prevent any gas from escaping.

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Factors that Affect Gas Pressure Temperature

• The affect of gas temperature on the pressure of
  a gas can be determined by using a pressure and
  temperature sensor
• How does a change in temperature affect the
  pressure of a gas?

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Factors that Affect Gas Pressure Volume

• The affect of gas volume on the pressure of the
  gas can be determined by using a syringe (marked
  in cc) and a pressure sensor.
• How does a change in volume affect the pressure
  of a gas?

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Pressure, Volume, and Temperature Lab

• Make a two Vee diagrams for this lab
• The first Vee diagram should focus on testing the
  affect of temperature on pressure
• The second Vee diagram should focus on testing
  the affect of volume on pressure

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Know
Found
Focus Question
Background
Value Claims
I.V D.V C. Hypothesis
Science Concepts
Knowledge Claims
Methods
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Temperature (T) vs. Pressure (P)

• Linear Relationship
• Pressure is directly proportional to Temperature
  (constant Volume)
• P?T

Pressure (kpa)
Temperature (C)
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Volume (V) vs. Pressure (P)

• Inverse Relationship
• Pressure is Inversely proportional to Volume
  (constant Temperature)
• P?1/V

Pressure (kpa)
Volume (cc)
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Why do gases behave this way?

• Make a whiteboard to explain the results of the
  lab
• Include diagrams of the gas particles and a
  description of the motion of the particles

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Volume vs. Pressure
Pressure (kpa)
Volume (cc)
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Volume vs. Pressure

• Use the inverse relationship to fill in the
  missing volume and pressure measurements.

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Volume vs. Pressure

• Multiplying the volume by the corresponding
  pressure results in a constant.

Etc
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Boyles Law

• States the pressure of a gas is inversely
  proportional to the volume of the gas if
  temperature remains constant
• Since both equations equal the same constant, you
  can set them equal to each other

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Pressure vs. Temperature

• What is the significance of the y-intercept?
• To eliminate the y-intercept we must adjust our
  temperature scale so that zero temperature zero
  pressure

Pressure (kpa)
Temperature (C)
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Pressure vs. Temperature

• The Kelvin temperature scale sets zero
  temperature at zero pressure.
• 0 K is called absolute zero
• 0 C 273K

Pressure (kpa)
Temperature (K)
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Pressure vs. Temperature
Pressure (kpa)
Temperature (K)
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Pressure vs. Temperature

• Use the linear relationship to fill in the
  missing temperature and pressure measurements.

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Pressure vs. Temperature

• Multiplying the initial temperature by the final
  pressure equals a constant

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Pressure vs. Temperature

• Since both equations equal the same constant, you
  can set them equal to each other
• Volume remains constant

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Volume vs. Temperature

• Solve the first equation for P1
• Solve the second equation for P2

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Charles's Law

• Since the two pressures are equal, you can set
  the two equations equal to each other
• Divide each side by pressure

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Charles's Law

• States the volume of a gas is directly
  proportional to the temperature of the gas if the
  pressure remains the same.