Temperature
Reading a Thermometer (°C)
Temperature is measured with a thermometer in degrees Celsius (°C). Water freezes at 0°C and boils at 100°C. Normal body temperature is about 37°C.
The higher the number, the hotter it is; the lower the number, the colder it is.
Example 1: At what temperature does water boil?
Water boils at 100°C.
Example 2: At what temperature does water freeze?
Water freezes at 0°C.
Quick recap
- Temperature is measured in degrees Celsius (°C).
- Water freezes at 0°C and boils at 100°C; body ≈ 37°C.
✓ Quick check
Normal body temperature is about ___ ?
Normal body temperature is about 37°C.
Ice melts at ___ ?
Ice melts (water freezes) at 0°C.
Difference in Temperature
The difference between two temperatures is found by subtracting the lower from the higher. If it is 35°C in the afternoon and 20°C at night, the difference is 35 − 20 = 15°C.
Example 1: Find the difference between 35°C and 20°C.
35 − 20 = 15°C.
Example 2: The temperature goes from 5°C to 25°C. By how much did it rise?
25 − 5 = 20°C.
Quick recap
- Difference = higher temperature − lower temperature.
- A rise increases the temperature; a fall decreases it.
✓ Quick check
What is the difference between 40°C and 28°C?
40 − 28 = 12°C.
What is 30°C − 18°C?
30 − 18 = 12°C.
Rise & Fall Problems
When the temperature rises, add the change; when it falls, subtract it. If it is 25°C and falls by 10°C, the new temperature is 25 − 10 = 15°C.
Example 1: The temperature is 25°C and falls by 10°C. What is the new temperature?
25 − 10 = 15°C.
Example 2: The temperature is 18°C and rises by 7°C. What is the new temperature?
18 + 7 = 25°C.
Quick recap
- Rise: add the change. Fall: subtract the change.
✓ Quick check
The temperature is 20°C and rises by 5°C. What is it now?
20 + 5 = 25°C.
The temperature is 12°C and falls by 4°C. What is it now?
12 − 4 = 8°C.
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