When the temperature decreases, the alcohol contracts and causes the metal marker on the minimum side of the tube to ‘retreat’ so that it marks the lowest temperature reached.
Average
2 Temperature
Temperature is measured in degrees Celsius/ Centigrade (°C) using an instrument called a thermometer. A special type of thermometer called a maximum and minimum thermometer (figure 3) is used in weather stations.
Centigrade: the old name for ‘Celsius’.
How a Maximum and Minimum Thermometer Works
The maximum and minimum thermometer is a U-shaped glass tube on which temperature readings are marked. The tube contains alcohol on its ‘minimum’ side, a vacuum (space) on its ‘maximum side’ and mercury in between. It also contains two metal markers inside the tubing on either side of the mercury. The metal markers show the maximum and minimum temperatures reached.
MIN °C
–10 –15 –20 –25
–8
0 5
3. A maximum and minimum thermometer
24 22 26 24 22 26 22 21 21
THIS AFTERNOON Temp (°C)
178
10 15 20 25 30 35 40
Alcohol Vacuum
Reset button
Metal markers
MAX °C
10 15 20 25 30 35 40
0 5
–5 –10 Mercury
–15 –20 –25
When the temperature increases, the alcohol expands and causes the metal marker on the maximum side of the tube to be pushed up so that it marks the highest temperature reached.
Being numerate:
What are the maximum and minimum readings shown on the maximum and minimum thermometer in figure 3? (Readings are taken from the bottom of the metal markers.)
Temperature on a Weather Map
On a weather map, average (mean) temperature for an area is displayed in the form of a number.
According to the weather map, what is the highest average temperature/s being experienced by Ireland on this particular afternoon, and where is it recorded? (Refer back to the map of weather stations on page 174 to help you if need be.) Which counties are experiencing the lowest temperatures? Why might this be the case?
