specific heat capacity

  • Created by: tia5sos
  • Created on: 06-12-20 21:09
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  • specific heat capacity
    • specific heat capacity relates temperature and energy
      • 1. heating a substance increases the energy in it's thermal energy store. You may sometimes see this referred to as the internal energy of a substance.
      • 2. in kinetic theory, temperature is a way of measuring the average internal energy of a substance.
      • 3. it take more energy to increase temperature of some materials than others.
        • eg. you need 4200J to warm 1kg of water by 1    , but only 139J to warm 1kg of mercury by 1
          • materials which need to gain lots of energy to warm up also release lots of energy when they cool down again.
            • they store lots of energy for a given change in temperature
      • 4. the change in the energy stored in a substance when you heat it is related to the change in its temperature by its specific heat capacity.
        • the specific heat capacity off a substance is the change in energy in the substance's therml store needed to raise the temperature of 1kg of that substance by 1
          • e.g. water has a specific heat capacity of 4200j/kg        this is high!!!
      • 5. you need to know how to use the equation relating temperature, energy, mass and specific heat capacity.
    • you can find the specific heat capacity of a substance (practical)
      • you can use this experiment to find the SHC of a liquid, e.g. water, or a solid e.g. a metal cylinder
      • 1. use a mass balance to measure the mass of your substance
      • 2. set up the experiment shown below. make sure the joulemeter reads zero.
      • 3. measure the temperature of the substance you're investigating, then turn on the power
      • 4. keep an eye on the thermometer. When the temperature has increased by e.g. 10 degrees, stop the experiment and record the energy on the joulemeter, and the increase in temperature.
      • 5. you can then calculate the specific heat capacity of your substance by rearranging the equation and plugging in your measurements
      • 6. repeat the whole experiment at least 3 times, then calculate the mean specific heat capacity of your substance
      • 7. you need to watch out for systematic errors due to energy escaping from your experiment.
        • the insulating container helps by reducing the amount of energy that escapes from the sides and the bottom of the substance you're investigating .
          • you could recue these energy loses further by adding a lid to the container.


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