Temperature is a measure
of the level of heat.
We all know what heat
feels like. You probably will say that you also know what cold
feels like, but cold is really just the absence of heat.
Temperature measures the level of heat and when the level is very low, we say it is
Heat is a form of
In any object that
possesses heat, the tiny particles of which it is made are in a state of vibration, constantly moving against
If you touch a piece of
hot metal, the vibrations in its molecules, those tiny particles, are transferred to your hand, which feels the
If we heat a kettle of
water, the molecules in the water vibrate more and more violently until they can no longer hold together as
water and turn into vapour, or steam.
If we put water into a
freezer, the molecules vibrate more and more slowly and lose their heat until the water turns into
You can see why we say
that heat is a form of energy.
If you were asked to
find out how much heat was in something, you would probably want to use a thermometer to measure its
however, does not tell us the amount of heat. It simply tells us the level of
heat. If you take two equal amounts of two liquids such as water
and mercury at the same temperature and heat them equally, the temperature of both of them will
The temperature of the
mercury, however, will rise 30 times more than the temperature of the water.
Whatever liquid you
choose, you will find that the same amount of heat will make its temperature rise faster than the temperature of
In other words, water
needs to be given more heat in order to raise its temperature. The
opposite is also true; water gives off heat without dropping very much in temperature.
of water and our climate
All day long the oceans
of our world are taking in heat from the sun’s rays, absorbing far more heat than any other substance
During the night, when
the temperature of the air above the oceans falls, they give some of this heat back to the air. Heat always flows from the warmer to the cooler
In the same way, some of
the heat which the seas absorb during the summer months is stored and slowly given back in the
The British Isles, for
example, are surrounded by water and the temperatures are much more even through summer and winter than those of
places surrounded by land.
The sea around the
British Isles acts like a great hot-water bottle, saving the islands from the extremely cold temperatures of
many places in Europe and Asia closer to the equator.
level of heat with a thermometer
If you are interested in
the weather, it is a good idea to keep a weather diary. Each day
write down what the weather was like (wet, dry, windy, sunny, cloudy) and make a note of the
temperature. You should take the temperature at the same time each
For this you will need
an outdoor thermometer. You must hang it in the shade so that the
sun’s rays do not touch it. You are measuring the level of heat in
the surrounding air, not the level of heat in the sun’s rays!
The temperature can be
read in one of two scales, the Fahrenheit scale, or the Celsius (sometimes called centigrade)
The freezing point of
water on the Celsius scale is 0
°(written as 0
°C.) and the freezing point of water on the Fahrenheit
scale is 32
°(written as 32
If you keep this record
for a whole year, you will be able to see what the extremes of
temperature are where you stay, that is, what the highest and lowest temperatures are over one
year. The thermometer below is showing the temperature on a warm
summer day. Can you see what the temperature