P1a- Heating Houses

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Temperature

Measurement of how hot something is using an abitrary/chosen scale. Unit of measuremt is degrees Celsius (°C)- can be Fahrenheit (°F) or Kelvin (°K).

The temperature of an object is a measurement of the average kinectic energy of the particles in the object.

Can be represented by colours in a thermogram- hottest areas are white/yellow/red; coldest areas are black/dark blue/purple.

Heat is a measurement of absolute energy, joules (j).

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Temperature Change

If a difference in temperature occurs between an object and its surroundings, heat energy will flow from the hotter region to the cooler region.

  • if temperature rises, it is taking in heat energy from surroundings until it reaches ambient temperature- room temp.
  • if temperature falls, it is giving out heat energy to surroundings until it reaches ambient temperature.

An object that has a very high temperature will cool down very quickly; as the temperature drops, it will fall at a slower rate.

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Measuring Heat Energy

The amount of energy needed to raise the temperature of an object depends on:

  • the mass of the object
  • the change in temperature required
  • the material it's made from

Total energy supplied= energy supplied per second x number of seconds.

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Specific Heat Capacity

Each material has a value of how much energy it can hold.

Specific heat capacity is the energy needed to raise the temperature pf 1Kg of materila by 1°C.

Energy(J)= Mass(Kg) x Specific Heat Capacity(J/Kg°C) x Temperature Change(°C)

Specific Heat Capacity=                  Energy                 

                                           Mass x Temperature Change

You may be required to rearrange this equation.

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Melting and Boiling

Energy is needed to melt or boil substances. This is why the temperature of a material doesn't change when it reaches the point of boiling, melting, or freezing (i.e. changing state)

This is was happens when an ice cube is melted:

  • Temp rises sharply at the start.
  • Once at 0°C, the temp stops rising as all the energy is being used to change state from solid to liquid. The temp will stay at 0°C until all of the ice has melted.
  • The temp then rises to 100°C.
  • The temp remains constant again whilst the water turns state from liquid to gas (steam)

Water temp will never be above 100°C, no matter how long it has been boiled for, but the temp of gas produced can rise.

During melting and boiling, the energy is use to break intermolecular bonds as the liquid changes state. This explains why the temp of the material doesn't change.

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Specific Latent Heat

The amount of heat energy required to melt/boil 1Kg of a material.

It depends on the material and the state.

The energy required can be found using this equation:

Energy (J) = Mass (Kg) x Spaecific Latent heat (J/Kg)

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