Grade 7 Mathematics MEASUREMENT – Temperature Notes
MEASUREMENT — Temperature
What is temperature?
Temperature tells us how hot or cold something is. In everyday life we measure temperature to know the weather, check if someone has fever, or cook food safely.
Common units
- Degrees Celsius (°C) — used in Kenya and most of the world. Water freezes at 0°C and boils at 100°C (at sea level).
- Degrees Fahrenheit (°F) — used in some countries (e.g. USA).
- Kelvin (K) — used in science. K = °C + 273.15 (you can use 273 for simple school work).
How to read a thermometer
There are different types: glass (mercury or alcohol), digital, and infrared. For a simple glass thermometer:
- Hold it steady and read the number level with the top of the column (the meniscus).
- Count small marks between numbers if the temperature is between two whole degrees.
- Always read at eye level.
Simple thermometer picture
The red column shows temperature. In this picture the level is about 25°C (near the 20 mark).
Tip: Clinical thermometers are small and read body temperature (~37°C).
Conversion between Celsius and Fahrenheit
Use these formulas:
- Celsius to Fahrenheit: F = C × 9/5 + 32
- Fahrenheit to Celsius: C = (F − 32) × 5/9
- Celsius to Kelvin: K = C + 273.15 (≈ C + 273)
Worked examples
Example 1: Convert 25°C to °F.
F = 25 × 9/5 + 32 = 25 × 1.8 + 32 = 45 + 32 = 77°F
Example 2: Convert 95°F to °C.
C = (95 − 32) × 5/9 = 63 × 5/9 = 315/9 = 35°C
Everyday examples (Kenya)
- Average daytime temperatures in many Kenyan towns: 20°C – 30°C.
- Body normal temperature: about 37°C. Fever is > 38°C.
- Water boils near 100°C at sea level; in high places (like some parts of Kenya) it boils a little lower.
Practice questions
- Read this thermometer: the top of the red column is at 18°C. Write the temperature.
- Convert 30°C to °F.
- Convert 86°F to °C.
- If water freezes at 0°C, what is this temperature in Kelvin?
- A child has a fever of 39°C. What is this in °F?
Answers
- 18°C.
- F = 30 × 9/5 + 32 = 54 + 32 = 86°F.
- C = (86 − 32) × 5/9 = 54 × 5/9 = 30°C.
- K = 0 + 273.15 ≈ 273 K.
- F = 39 × 9/5 + 32 = 70.2 + 32 = 102.2°F (about 102.2°F).
Key points to remember
- Temperature shows how hot or cold something is. Use °C in Kenya for school work.
- Read thermometers at eye level and use the top of the liquid column for glass thermometers.
- Use the conversion formulas when you need to change units.
- Practice with real thermometers (weather or classroom) to become confident.
Prepared for Mathematics — Measurement | Subtopic: Temperature (age 12, Kenyan context)