When you heat something up you are giving it heat energy.
This heat energy raises the temperature of the object that you are heating and so we can say
that the rise in temperature is a good guide to the amount of heat energy that we have put in
– more energy the greater the rise in temperature.
If you do some simple experiments on heating things you will quickly
realise that for the same amount of heat energy put in (say using a certain Bunsen burner for
a certain amount of time) the rise in the temperature of different objects is different. The rise
in temperature will depend on three things:
(a) the amount of heat energy that you put
in
(b) the amount (mass) of the object that you are heating
(c) the material from
which the object is made.
The more massive the object the more heat energy it
needs to raise its temperature by a certain amount. For example it takes twice as much
energy to heat 400 g of water from 20oC to 100oC as it does to heat 200 g of water from 20oC
to 100 oC.
Think about how that affects the material that saucepans
are made from.
The difference between heat energy and temperature is very
obvious if you think about a candle flame and beaker of boiling hot water. The candle flame
is at a much higher temperature (about 900oC) but there is a lot more heat energy 'locked
away' in the beaker of boiling hot water.
Once you have got something hot it is
important to try and keep it hot. It is for this reason that insulation jackets are put round hot
water tanks.
When you heat something steadily its temperature also rises steadily.
However there is always going to be some heat energy lost to the room. The bigger the
difference between the temperature of the object being heated and the temperature of the
room the faster the object will cool.