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Unit 28 - Heat And Temperature

Unit 28 - Heat And Temperature



Heat and Temperature

Heat and Temperature



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    Unit 28 - Heat And Temperature Unit 28 - Heat And Temperature Presentation Transcript

    • Heat and Temperature
      Unit 28
    • Temperature
      Temperature is a measure of the average Kinetic Energy of the particles in a substance.
      Remember KE is the energy of motion.
      The higher the average Kinetic Energy, the faster the particles move
      Temperature and Heat are NOT the same thing
      View these sites for more on temperature
      Temperature and Temperature Scales
    • Temperature Scales
      There are 3 Types of Temperature Scales
      Celsius Fahrenheit
    • Fahrenheit Scale
      Most commonly used in United States. (originated in Great Britain)
      Non-metric system scale
      Not usually used in science
      Visit these “cool” web sites
      Converting between oF and oC
      Fahrenheit and Celsius Scales
      History of Fahrenheit Scale
    • How Fahrenheit Works
      Water freezes at 32°F
      Water boils at 212°F
      Zero was based on the lowest they could get water to stay liquid at the time
      (with salt in it).
      100° was based on the highest it was believed humans could survive at the time
    • Celsius Scale
      Based on Metric System Scale
      Most used in the world, including Canada, Europe, and Asia
      Visit these “cool” web sites
      History of Celsius Scale
      Converting between oF and oC
      Anders Celsius
    • How Celsius Works
      Water freezes at 0°C
      Water boils at 100°F
      Absolute zero is -273°C
    • Kelvin Scale
      Actual Metric System scale.
      Most often used in Laboratory settings for calculation purposes.
      There are no negative temperatures.
      A change (Δ) of 1oC = 1 K.
      Converting from oC to K
      William Thomson
      Baron of Kelvin
    • Absolute Zero
      Defined as 0 Kelvin.
      Average temperature of space is 2.7K
      Scientists have gotten within fractions of absolute zero, but it is impossible to ever completely stop the movement of an atom, since that means it has zero energy.
      Boomerang Nebula contains the coldest known temperature in the universe at 1K
      Helium can only become a gas at below 5K
    • Temperature Scale Comparisons
      373 K = 100°C
      37°C = 99°F
      298 K = 25°C
      273 K = 0°C
      -40°C = -40°F
      0 K = -273°C
    • Heat Transfer
      Conduction, Convection, and Radiation
    • Types of Heat Transfer
    • Conduction
      Takes place between solids or solids with liquids
      Particles vibrating or moving faster transfer some of their energy to nearby atoms
    • Conduction
      When particles collide and the faster ones pass some of their energy on to the cooler ones.
      This results in a change in energy for each particle
      This causes the faster ones to slow down and cool
      The slower ones speed up and heat up
    • Examples of Conduction
      Conduction requires direct contact
    • Convection
      Occurs in Fluids (liquids and gases)
      Caused by a change in density due to a change in temperature.
    • Convection con’t
      The warmer fluid expands, becomes less dense and rises.
      The cooler fluid contracts, becomes more dense and sinks.
    • Convection con’t
      Lava Lamps are an example of convection that you have probably seen before.
    • Importance of Convection
      Convection causes warm water vapor to rise, condense into clouds when it cools,
      and then falls back as rain
      Without convection, there would be no rainfall and thus no plants
    • Examples of Convection
      Magma in the mantle rises due to convection.
      The heat from the core heats it and then it rises to form volcanoes on the surface
    • Radiation
      The transfer of energy due to Infrared and other electromagnetic rays.
      Radiation can travel through space.
      All things radiate heat.
    • Why are light bulbs hot?
      They produce infrared radiation in addition to visible light
      Infrared transfers energy to the molecules that makes them vibrate faster (thus hotter)
    • Thermal Expansion
      When objects heat up their particles move faster, hit others harder, and bounce further, creating more empty space between the particles.
      As a result, the entire substance expands.
      This is known as thermal expansion
    • Examples of Thermal Expansion
      Roads crack as they expand in the heat
      On bridges and other sensitive sections, expansion panels allow it to flex.
    • Thermal Expansion continued
      The liquid in a thermometer expands as it warms.
      This causes it to head up the tube and tell you the temperature
    • Heat Transfer
      Heat Conductors
      Good thermal conductors transfer heat rapidly
      Metals are good thermal conductors
      Radiators are metals that transfer the heat in the water to the air
      Frying pans transfer heat from the stove to the food
    • Heat Transfer
      Thermal Insulators
      Poor thermal conductors of heat.
      Asbestos, cork, ceramic, cardboard, and fiberglass are examples of thermal insulators