heat13mix

EnergyHeatradiationconductionconvection
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heat13mix

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  1. Heat and Heat Technology

    Slide 1 - Heat and Heat Technology

    • Chapter 10
  2. How do you get your body warmer?

    Slide 2 - How do you get your body warmer?

  3. Temperature

    Slide 3 - Temperature

    • Temperature: Measures averagekinetic energy; the more kinetic energy the warmer the object
  4. Thermometer

    Slide 4 - Thermometer

    • Instrument used to measure temperature
    • Usually filled with alcohol or mercury
    • Degree is the unit used to measure temperature
  5. Temperature Scales

    Slide 5 - Temperature Scales

    • Fahrenheit scale commonly used in the U.S.
    • Freezing is 32° and boiling is 212°
    • Celsius scale is used in science
    • Freezing is 0° and boiling is 100°
    • Kelvin scale is based upon absolute zero, no negative temperatures
    • Freezing 273 K and boiling 373 K
    • Scientist use this scale because 0 K is the lowest temperature possible, it has never been reached (theoretical)
  6. Temperature Conversions

    Slide 6 - Temperature Conversions

    • C is Celsius F is Farenheit 
    • C = 5/9 (F-32) F = 9/5 (C+32
    • Let's try converting 68 degrees Farenheit to celsius 5/9(68-32)
    • Step 1: 68 less 32 is 36Step 2: 5 divided by 9 is 0.5555555555555Step 3: multiply the repeating decimal by 36Step 4: your solution is 20
    • Now, convert 20 degrees Celsius to Farenheit to check your work.
    • 9/5C +32Step 1: 9 divided by 5 is 1.8Step 2: 1.8 multiplied by 20 is 36Step 3: 36 plus 32 = 68
    • C to K C = K + 273
  7. Thermal Expansion

    Slide 7 - Thermal Expansion

    • Most substances (all phases) expand when the temperature is increased
    • However; water expands as it cools from 4° C to 0° C. Ice becomes less dense than liquid water
  8. Thermostat

    Slide 8 - Thermostat

    • Thermostat is used to change temperature of a heater
    • Bimetallic strip is used inside to sense the change in temperature. Two metals are joined together, each having its own rate of expansion. It coils or uncoils reaction to heat turning the electric circuit on or off
  9. Heat

    Slide 9 - Heat

    • Is the energy transferred between objects that are at different temperatures
  10. Thermal Energy

    Slide 10 - Thermal Energy

    • The sum of the potential energy and the kinetic energy of all the molecules in an object measured in joules
  11. Heat Transfers: Conduction

    Slide 11 - Heat Transfers: Conduction

    • Heat is transferred through a substance by direct contact
    • Works best in solids because all the atoms are touching
  12. Thermal conductors and thermal insulators

    Slide 12 - Thermal conductors and thermal insulators

    • Conductors- iron, aluminum, copper, and silver
    • Insulators- wood, plastic, rubber, and air
  13. Convection

    Slide 13 - Convection

    • Takes place in liquids and gases
    • It is the up and down movement called convection currents
    • Heated material rises because it is less dense
  14. Radiation

    Slide 14 - Radiation

    • Heat is transferred through empty space
    • Ex: heat from the sun, an open fire, or heater
  15. Specific Heat

    Slide 15 - Specific Heat

    • The amount of heat required to raise the temperature of 1 gram of a substance by 1° C, expressed as calories/gram
    • Water 1.00 cal/gr
    • Aluminum 0.22 cal/gr
    • Mercury 0.03 cal/gr
  16. Calculating Heat Energy

    Slide 16 - Calculating Heat Energy

    • Heat gained or lost =
    • mass * T * Specific heat
    • ( T change in temperature either + or -)
    • How much energy would it take to raise the temperature of 4 grams of aluminum from 0° to 5°?
    • 4g * 5° * 0.22 = 4.4 cal
  17. Phase Changes

    Slide 17 - Phase Changes

    • A change in phase requires heat energy but temperature does not rise until the phase change is complete
    • ice melts to water
    • water vaporizes to a gas
  18. Slide 19

    • Heat of Fusion from a solid to a liquid
    • Freezing point of water is 0° C and the melting point of ice is 0°
    • Heat of vaporization from a liquid to a gas
    • Vaporizing point of a liquid in 100° C and the condensation point of a gas
    • is 100° C
    • During a phase change there is only a change in energy not temperature
  19. Calories

    Slide 20 - Calories

    • The scientific "calorie" is spelledwith a lower-case "c".One "calorie" = 4.184 Joules---------------------------------------------The "dieter's" calorie is spelledwith an upper-case "C".One "Calorie" = 1000 calories
    • Calorie is the quantity of heat required to raise the temperature of 1 gram of liquid water 1 degree Celsius
    • 1 calorie = 4.2 joules
  20. Heating Systems

    Slide 21 - Heating Systems

    • Hot water can be used to heat a room by the heat being radiated through pipes
    • Warm air heating, a furnace heats the air and it is circulated through the room
    • Solar energy collectors are placed on the roof and collect the energy in water
  21. Heat Engines

    Slide 22 - Heat Engines

    • External heat engines
  22. Slide 23

    • Internal heat engine
  23. Slide 24

    • Cooling systems