Heat vs. Temperature

Heat
Temperature

Do NOT confuse the two - they are linked but NOT the same.

Input of heat to a system usually results in an increase of temperature but NOT where there is a change of state involved - see latent heat

High temperature of an object does not necessarily mean a lot of heat has been given to it. Heat a thimble of water until it boils and then give the same amount of heat to a bath of water - you won't even detect a change in temperature in the bath of water!

How much heat energy is needed to raise the temperature of 1kg of a substance is called the specific heat capacity. The SHC helps us compare how easy it is to heat up different substances.

Experiments that investigate heat transfer between substances is called calorimetry

Heat is a form of energy. Temperature is a measure of how hot or cold things are.
Difference in temperature makes heat energy move from a hot part to a cold part of an object.
It is measured in joules (J).

It is measured in degrees.

The Celsius and kelvin scales of temperature are used in science but there are others such as centigrade and fahrenheit.

Try the Dalek temperature scale!

  Pure ice melts at 0oC or 273K
  Pure water boils at 100oC or 373K at Sea Level - see here for what happens at different altitudes
It can be measured with a joule-meter or a combination of instruments, the readings of which can be used to perform a calculation to establish the value. It is measured with a thermometer.
 

There are many different kinds of thermometer, their range, sensitivity and constuction varies widely.

A thermometer can be made from anything which responds to temperature change.

You should know about the liquid in glass thermometer in detail. This uses expansion of liquids with temperature rise.

Heat always flows from hot areas to cold areas (See U-values )  
The bigger the difference in temperature between two objects the faster the heat will move (See the pressure cooker )  
The bigger the area of contact between the two objects the faster the heat transfer will happen  
Heat moves easily through good conductors of heat (such as metals) and very slowly through heat insulators (such as trapped air pockets, wood or plastic). See double glazing and cavity wall insulation. The temperature of an object made of a good conductor of heat tends to be the same throughout the object but an insulator will be much hotter near the heat source than it is elsewhere.
Heat radiation is absorbed/emitted readily by dark, dull, rough surfaces and less easily by light, shiny, smooth surfaces.
The temperature of dark, dull, rough surfaces will rise quickly if irradiated with infra red heat radiation and light, shiny, smooth surfaces will not respond as quickly. The hot surfaces will then cool at a similar rate to the way they rose in temperature when the heat source is taken away.
There are three methods of heat transfer: conduction, convection and radiation As temperature rises an object usually expands. Click here for a question sheet on expansion.





The Laws of Thermodynamics 

Heat is often an unwanted product of energy changes in a device. Click here to find out about 'heat sinks' or 'cooling fins'.

Now revise the topic from flash cards I have written for: