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Everyday maths 1

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# 5.2 Understanding temperature

Using the right temperature is often a matter of safety. For example, a piece of machinery may not be able to operate properly below a minimum temperature or above a maximum temperature, or a jar of tablets may include advice on its label about what temperature it should be stored at.

Figure 41 Warning labels

Temperatures used to be shown in degrees Fahrenheit. You will still see these measures sometimes. For example:

Figure 42 Temperatures in Celsius and Fahrenheit

Note: Fahrenheit is still used in the USA.

Here are some temperatures in Celsius and Fahrenheit:

Celsius Fahrenheit
–18 0
0 32
10 50
20 68
30 86
40 104
50 122

Take a look at the example below for comparing temperatures.

## Example: Safe storage

You have instructions with chemicals sent from the USA that they must be stored at between 50 and 70°F. The thermometer on the storage tank shows the temperature in degrees Celsius.

Figure 43 Using a thermometer in safe storage

Are the chemicals stored safely?

### Method

Looking at the temperature comparison chart, 13°C falls in the following range:

• 10°C = 50°F
• 20°C = 68°F

13°C falls between 10°C and 20°C, meaning that it is also in the range between 50°F and 68°F. The chemicals are stored safely.

Now try the following activity. Remember to check your answers once you have completed the questions.

## Activity 13: Celsius and Fahrenheit

1. A recipe for meringue says you must cook it at 150°C. Your cooker shows temperatures in Fahrenheit. What should you set it to? (Use the conversion chart below to help you.)
Celsius Fahrenheit
100 212
150 302
200 392
250 482
300 572
350 662
1. The thermometer on an old freezer shows the temperature in degrees Fahrenheit.
Figure 44 Converting temperatures on old thermometers

A pack of food has a warning that it must be stored between –12°C and –25°C. Is the food stored safely? (Use the conversion chart below to help you.)

Celsius Fahrenheit
–30 –22
–20 –4
–15 5
–10 14
–5 23
0 32
10 50
1. A machine must be turned off if the temperature rises above 600°F. Using a Celsius thermometer, you find out that the temperature of the machine is:
Figure 45 A thermometer

Is it safe to leave it turned on? (Use the conversion chart below to help you.)

Celsius Fahrenheit
0 32
50 122
100 212
150 302
200 392
250 482
300 572
350 662
400 752