Measuring Temperature
Class 6 Science · Chapter 7: Temperature and its Measurement · NCERT Curiosity section 7.3
Learn
Tenzin has a fever. His mother uses a clinical thermometer, made for measuring body temperature. Its scale goes only from 35 °C to 42 °C, because a human body temperature stays in this range. Each small mark is 0.1 °C.
Normal body temperature is about 37 °C. Tenzin's reading is 38.4 °C: higher than normal, so he has a fever. A clinical thermometer has a kink that stops the liquid from falling back, so you can read it after taking it out. Digital thermometers show the number on a screen.
To measure hot water or the air, we use a laboratory thermometer, about −10 °C to 110 °C. It has no kink, so read it while the bulb is still in the liquid, with your eye level with the top of the liquid. Never use a clinical thermometer for hot water: it can break!
Explore: use the thermometers.
- Show a normal body temperature: 37.0 °C.
- Show a fever of 38.6 °C.
- Put the steps for using a clinical thermometer in order.
Remember
- Clinical thermometer: 35–42 °C, for body temperature. Laboratory thermometer: about −10 to 110 °C.
- Normal body temperature is about 37 °C; read a lab thermometer with its bulb still in the liquid.
Quick check
Which thermometer should you use to measure the temperature of boiling water?
- A laboratory thermometer
- A clinical thermometer
- Either one
- Your hand
Answer
A laboratory thermometer. A clinical thermometer only goes to 42 °C and could break.
Think about it
Why is a clinical thermometer shaken before use, but a laboratory thermometer is not?
One answer
The kink in a clinical thermometer stops the liquid from falling back on its own, so it must be shaken down below 35 °C before the next reading. A laboratory thermometer has no kink; its liquid falls by itself.
Practice
Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.