1. Temperature

2. DEFINITION
Temperature is the degrees of “HOTNESS” or
“COLDNESS” of a body.
If something measuring temperature reads 100°C, this does not say how
much heat is present, only its level of HOTNESS.
10 litres of water at 100°C would contain more heat than 1 litre of water at
100°C.
Scales
Fahrenheit Not used as much now
Celsius
Kelvin
Sometimes called centigrade, usually written as “C”
0K = Absolute Zero
At 0K a gas would be reduced to nothing.

3. Temperature measuring tools
To produce a temperature scale, a minimum of two fixed points is required.
The two fixed points on the Celsius scale of temperature are:
• melting point of ice
• boiling point of water.
A tool which is used to measure low temperatures is called a thermometer.
Most substances expand when heated and contract when cooling.
One of the most common ways of measuring temperature is to use this fact.

4. Glass thermometer
100°C
0°C
Sealed tube
containing
mercury or alcohol
Mercury and alcohol are used in
thermometers. They expand
with a rise in temperature.
They contract with a fall
in temperature
The range between the freezing and
boiling temperature is large. Mercury
freezes at -39°C and boils at 375°C.
Alcohol freezes at –112°C and boils at
78°C. Mercury thermometers are used
to measure high temperatures.

5. The SI unit of temperature is the A temperature of one Kelvin is
exactly equal to one degree Celsius. The diagram shows the relationship
between the temperature scales.
“KELVIN”.
The scales are different but
the temperature intervals
(each single degree) are the
same.
Kelvin
Celsius/
Centigrade Fahrenheit
273K Freeze Point
of water
0K
0°C 32°F
-273°C
100°C 212°F373K
180Divisions
100Divisions

6. Temperature conversion
chart
The point -40°C and -40F
meet. This gives a quick
way of converting.
0
212
32
100-40
Degree C
Degree F

7. These are the scales at atmospheric pressure (1013mb)
TEMPERATURE SCALES
Celsius
Centigrade
Fahrenheit
Freezing Point
Boiling Point
0K = -273°C absolute zero
273K = -0°C the ice point of water (change of state)
373K = 100°C the steam (gas) point (change of state)
0 32
212100

8. Changing scales
Both scales are still widely used and conversion from one to the other is
sometimes necessary. To convert:
Centigrade to Fahrenheit = °C x 9/5 + 32
Fahrenheit to Centigrade = (°F - 32) x 5/9
An “rough” method of conversion:
Centigrade to Fahrenheit =
Fahrenheit to Centigrade =
°C x 2 + 30
°F - 30
2

9. By using your conversion formulas, complete the following table.
°F °C
Freezing point of water 32
Boiling point of water 100
Hot water storage temperature 60
Normal room temperature 70
Normal showering temperature 40
Melting point of lead 327
0
212
140
21
104
620

10. Temperature can be measured using a number of tools. Name
TWO.
1)
2)
Name TWO tools used to control the
temperature of water in a central heating system.
1)
2)
THERMOMETER
THERMOCOUPLE
CYLINDER THERMOSTAT
BOILER THERMOSTAT

11. Convert these temperatures:
 -60°C to F
 8°C to F
 2°C to F
 120°F to C
 15°F to C

12. ANSWERS
 -60°C to F = 76°F
 8°C to F = 46.4°F
 2°C to F = 35.6°F
 120°F to C = 48.8 °C
 15°F to C = -9.4 °C