Temperature and its Measurement — Class 6 Science (Curiosity)
1. About This Chapter
Chapter 7 starts with Lambok and his sister Phiban — Lambok might have a fever, and they use a thermometer to check. This simple story sets the stage for understanding temperature: what it means, how we measure it, and why our sense of touch alone is not reliable. The chapter covers clinical and laboratory thermometers, the Celsius scale, and real-world applications.
2. Hot and Cold — Touch Is Not Reliable
Our sense of touch can mislead us about temperature:
The Three-Bowl Activity:
- Bowl 1: Hot water
- Bowl 2: Lukewarm water (room temperature)
- Bowl 3: Cold water
Put one hand in hot water and the other in cold water for a minute. Then put BOTH hands in Bowl 2 (lukewarm). The hand that was in hot water feels cold; the hand that was in cold water feels warm. Same water, different sensations!
This proves we need instruments — thermometers — for accurate temperature measurement.
3. What Is Temperature?
Temperature is a measure of how hot or cold an object is. It tells us the degree of hotness or coldness, not just a feeling.
The Celsius Scale:
- Unit: degree Celsius (°C)
- Water freezes at 0°C
- Water boils at 100°C
- Normal human body temperature: 37.0°C
4. Clinical Thermometers
Clinical thermometers measure body temperature:
Features:
- Range: typically 35°C to 42°C (relevant for body temperature)
- Has a kink — prevents mercury/alcohol from falling back immediately
- Digital thermometers are now more common — safer and easier to read
How to Use:
- Wash the tip before and after use
- Place under the tongue or in the armpit
- Wait for the reading to stabilize
- Read at eye level
Non-Contact Thermometers:
Used during the COVID-19 pandemic — they measure temperature from a distance using infrared technology.
5. Laboratory Thermometers
Laboratory thermometers are different from clinical ones:
| Feature | Clinical | Laboratory |
|---|---|---|
| Range | 35°C to 42°C | -10°C to 110°C |
| Liquid | Mercury/Alcohol | Alcohol or mercury |
| Use | Body temperature only | Science experiments |
| Kink | Present | Absent |
Safety:
- Handle with care — they are fragile
- Never use a clinical thermometer for boiling water — it will break!
6. Different Temperature Scales
While Celsius (°C) is commonly used, other scales exist:
- Fahrenheit (°F) — used in some countries like the USA. Water freezes at 32°F, boils at 212°F
- Kelvin (K) — the scientific (SI) unit. 0 K is absolute zero (−273.15°C), the coldest possible temperature
The chapter introduces these scales so students understand that temperature can be expressed in different ways.
7. Recording and Analysing Temperature Data
Students are encouraged to:
- Record daily maximum and minimum air temperatures over 10 days
- Observe patterns — which days are warmer, which are cooler
- Understand the importance of air temperature in weather reports
8. Key Concepts Summary
| Concept | Description |
|---|---|
| Temperature | A measure of how hot or cold something is |
| Celsius (°C) | Water freezes at 0°C, boils at 100°C |
| Clinical Thermometer | For body temperature (35°C–42°C), has a kink |
| Laboratory Thermometer | For experiments (−10°C to 110°C), no kink |
| Normal Body Temp | 37.0°C |
9. Important Vocabulary
- Temperature: A measure of hotness or coldness of an object
- Thermometer: An instrument used to measure temperature
- Celsius Scale: Temperature scale where water freezes at 0°C and boils at 100°C
- Clinical Thermometer: Thermometer designed to measure body temperature
- Laboratory Thermometer: Thermometer for experimental use with a wider range
10. Worked Questions
Q: Why can't we rely on touch to judge temperature accurately? Our sense of touch is relative. The same lukewarm water feels warm to a cold hand and cold to a warm hand. We need a thermometer for an objective, accurate measurement.
Q: What happens if you use a clinical thermometer to measure boiling water? The clinical thermometer's range is only up to 42°C. Boiling water at 100°C will cause the liquid inside to expand rapidly and the thermometer will break.
Q: What is normal human body temperature? Normal human body temperature is about 37.0°C (98.6°F). It can vary slightly — a reading above 38°C generally indicates fever.
11. Conclusion
Temperature and its Measurement teaches students that science relies on precise instruments, not just human senses. The chapter builds practical skills (how to read a thermometer), scientific concepts (Celsius scale, different thermometer types), and data analysis habits (recording and interpreting temperature data) — all essential for future science education.
