Heat
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Heat. The motion of the particles of matter. Heat Transfer. Heat flows from an area of high heat to an area low in heat. Three methods of heat transfer. Conduction: Transfer from one substance to another by direct contact of molecules. Example: When you touch a hot stove. Convection:

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Heat

Heat

The motion of the particles of matter


Heat transfer

Heat Transfer

  • Heat flows from an area of high heat to an area low in heat.


Three methods of heat transfer

Three methods of heat transfer

Conduction:

  • Transfer from one substance to another by direct contact of molecules. Example: When you touch a hot stove.

  • Convection:

    • Heat carried from one place to another in a liquid or gas as molecules move in currents caused by density differences. Example: Warm air rising.

  • Radiation:

    • Heat carried through empty space in the form of infrared rays. Example: When you face the sun and feel warmth on your face.


  • Temperature

    Temperature:

    • A measure of the average kinetic energy of molecules.

    • The faster the molecules of a substance are moving, on average, the higher the temperature.

    • Thermometer - An instrument for measuring temperature.


    How do you set a temperature scale watch the videos below

    How do you set a temperature scale? (watch the videos below!)

    • How Fahrenheit made his Temperature scale-

    • The Celsius Scale

    • Fahrenheit based it on his own body temperature (100°F) and the freezing point of saturated salt water.

    • Celsius based it on the boiling point of water (100°C) and the freezing point of water.

    • Kelvin has the same degree scale as Celcius, but starts at absolute zero.—no negative temperatures!


    Temperature scales

    Temperature Scales:

    • Celsius -

      • Most common scale world wide - Used in all scientific measurements.

      • Freezing point of water is 0o C.

      • Boiling point of water is 100o C.

    • Kelvin -

      • An "absolute" scale used for kinetic theory calculations.

      • Zero on this scale, 0 K, is the lowest possible temperature.

      • Note the way the temperature is written, 0 K. This is read as "zero kelvins", without using the word degrees.

      • To convert Celsius degrees to kelvins, add 273 to the Celsius temperature.

    • Fahrenheit -

      • The temperature scale generally used in the United States.

      • Freezing point of water is 32 oF.

      • Boiling point of water is 212 oF.

      • While converting between oC and oF is not stressed in this class, a "ball park" conversion would be oC = (oF - 30) / 2. While this gives a Celsius temperature that is a little low, it is a quick way to compare the two scales.


    Absolute zero

    Absolute Zero

    • - The lowest possible temperature.

    • The temperature would be 0 K or about -273 oC.


    Calorie

    Calorie:

    • The unit of heat.

    • The amount of heat needed to raise the temperature of one gram of water one degree Celsius.

    • A "Food Calorie" is 1000 calories, or a Kilocalorie


    Specific heat

    Specific Heat

    • The ability of a substance to absorb heat.

    • Number of calories needed to raise the temperature of one gram of the substance one Celsius degree.

    • The units of Specific Heat are - calories per gram Celsius degree.


    Equation

    EQUATION

    Q = cm DT

    DT = final T – initial T

    • Heat gain/lost =(mass) (change in Temp) (spec. heat)

    • Specific heat of water

      c = 1 calorie/gram°C


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