NCERT Solutions Curiosity Chapter 7 .3.2 Laboratory thermometer — Activity 7.3: Let us observe
Book page 1307 Updated on2026-09-05
Q1.
Note down the following: — What is the lowest temperature it can measure?
Answer
For the laboratory thermometer shown in Fig. 7.3a, the lowest mark on the scale is –10 °C.
To find it on your own thermometer, hold it upright and look at the bottom end of the scale, just above the bulb. The first number printed there is the lowest temperature it can measure.
A laboratory thermometer. The scale runs from –10 °C to 110 °C, so its range is 120 °C. Each small division here stands for 2 °C.
Check it yourself: Not every laboratory thermometer is the same. Some start at 0 °C, some at –10 °C, a few at –20 °C. Always read the actual scale of the thermometer in your hand before you use it.
Q2.
What is the highest temperature it can measure?
Answer
For the thermometer in Fig. 7.3a, the highest mark on the scale is 110 °C.
It is found at the top end of the scale, farthest from the bulb.
Why 110 °C and not 100 °C: water boils at about 100 °C. The scale is carried a little past that so that boiling water — and steam just above it — can still be measured without the liquid running off the end of the scale.
Q3.
So, the range of this thermometer is _______ . Now look at the thermometer shown in Fig. 7.3a carefully. Can you tell its range?
Answer
The range of a thermometer is written as “lowest mark to highest mark”.
Lowest temperature = –10 °C Highest temperature = 110 °C Range = –10 °C to 110 °C Size of this range = 110 °C – (–10 °C) = 110 °C + 10 °C = 120 °C
So the thermometer of Fig. 7.3a can measure any temperature from –10 °C to 110 °C, and no temperature outside it.
Tip: Do not confuse range with smallest value. Range tells you how far the thermometer reaches; the smallest value tells you how finely it can read. This thermometer reaches 120 °C wide and reads to the nearest 1 °C.