Class 6 Science · Chapter 7

7. Temperature and its Measurement

Answers to in-text questions, activities and Let us enhance our learning. NCERT Curiosity, Class 6 Science (CBSE).

Activities and In-text Questions

Can it always be correctly judged that a person has fever only by touching the person?

No. Our sense of touch is not reliable. We must use a thermometer to measure temperature.

7.1Dip your right hand in warm water (A) and left hand in ice-cold water (C). Then put both hands in tap water (B). What do you feel?

The right hand (from warm water) feels that water in B is cool.

The left hand (from ice-cold water) feels that the same water in B is warm.

Inference: We cannot always rely on our sense of touch to decide whether a body is hot or cold.

7.2Measure the body temperature of yourself and your friends with a digital clinical thermometer (Table 7.1).

Name	Temperature (°C)
Myself	36.8
Friend 1	37.0
Friend 2	36.9
Friend 3	37.1
Friend 4	36.7

The temperature of every person is not exactly 37.0 °C. Normal temperature is the average body temperature of many healthy people. It depends on age, time of the day and activity.

These are sample readings. Record your own.

A digital thermometer shows the normal temperature of a healthy human body as 98.6 °F. What is the reason for this difference?

It uses a different scale, the Fahrenheit scale. 37.0 °C on the Celsius scale is the same as 98.6 °F on the Fahrenheit scale.

Can a clinical thermometer be used for measuring the temperature of boiling water or ice?

No. The temperatures of boiling water and ice are outside the range of a clinical thermometer. A clinical thermometer is used only for body temperature.

7.3 & 7.4Find the range and the smallest value that the laboratory thermometer in Fig. 7.3 can read.

Lowest temperature = −10 °C. Highest temperature = 110 °C. So the range is −10 °C to 110 °C.

Temperature difference between two bigger marks = 10 °C. Number of small divisions between them = 10.

One small division = 10 ÷ 10 = 1 °C. This is the smallest value it can read.

7.5Why does the level of the liquid begin to fall as soon as you take the thermometer out of warm water?

Outside the water, the thermometer cools down. So the temperature must be read while the thermometer is still in the water.

What are the temperatures of ice and boiling water? Do they change after some time?

Melting ice shows about 0 °C. Boiling water shows about 100 °C.

The temperature of ice remains constant while it is melting. The temperature of water remains constant while it is boiling.

7.6Why are there differences in the boiling water readings of different students?

All the students may not have followed the correct way of reading the thermometer.

The thermometer may have been tilted.
The bulb may have touched the bottom or side of the beaker.
The eye may not have been in line with the level of the liquid.

7.7Do the maximum and minimum air temperatures stay at the same level during these days?

No. They usually vary every day because weather depends on many factors. Temperature generally rises as summer comes and falls in winter.

Let us enhance our learning

1The normal temperature of a healthy human being is close to ____.

(ii) 37.0 °C

237 °C is the same temperature as ____.

(iv) 98.6 °F

3Fill in the blanks.

(i) The hotness or coldness of a system is determined by its temperature.

(ii) The temperature of ice-cold water cannot be measured by a clinical thermometer.

(iii) The unit of temperature is degree Celsius.

4The range of a laboratory thermometer is usually ____.

(ii) −10 °C to 110 °C

5Four students used a laboratory thermometer to measure the temperature of water (Fig. 7.6). Who followed the correct way?

(ii) Student 2

Student 2 held the thermometer vertically. Its bulb was in the water but did not touch the bottom or the sides.

Student 1 held the thermometer tilted.
In Student 3’s case, the bulb touched the bottom of the beaker.
In Student 4’s case, the bulb touched the side of the beaker.

6Colour to show the red column on the drawings of thermometers as per the temperatures 14 °C, 17 °C and 7.5 °C.

Each small division = 1 °C. The red column ends at 14 °C, 17 °C and 7.5 °C.

Each small division is 1 °C. For 14 °C, colour up to the 4th small mark above 10. For 17 °C, colour up to the 7th small mark above 10. For 7.5 °C, colour up to the middle of the 7th and 8th small marks above 0.

7Observe the part of the thermometer shown in Fig. 7.8 and answer.

(i) It is a laboratory thermometer. Its scale starts below 0 °C (from −10 °C).

(ii) The reading is 26 °C.

(iii) There are 10 small divisions between 0 and 10. So it can measure 1 °C.

8A laboratory thermometer is not used to measure our body temperature. Give a reason.

The liquid in a laboratory thermometer starts falling as soon as it is taken out. We cannot read it while it is in the mouth. So it does not give the correct body temperature.

9Study Vaishnavi’s body temperature record (Table 7.4).

(i) Highest recorded temperature: 40.0 °C

(ii) It was recorded on Day One at 7 pm.

(iii) Her temperature returned to normal on Day Three (37.0 °C at 4 pm).

10If you have to measure the temperature 22.5 °C, which of the three thermometers (Fig. 7.9) will you use? Explain.

I will use thermometer (b).

Thermometer (b) has 20 small divisions between 0 °C and 10 °C. So each division is 0.5 °C, and it can read 22.5 °C.

Thermometer (a) reads only 1 °C and (c) reads only 2 °C. They cannot show 22.5 °C correctly.

11The temperature shown by the thermometer in Fig. 7.10 is ____.

(ii) 27.5 °C — the red column ends midway between 27 °C and 28 °C.

12A laboratory thermometer has 50 divisions between 0 °C and 100 °C. What does each division of this thermometer measure?

Each division = 100 °C ÷ 50 = 2 °C

13Draw the scale of a thermometer in which the smallest division reads 0.5 °C. Draw only the portion between 10 °C and 20 °C.

From 10 °C to 20 °C there are 20 small divisions. Each small division = 0.5 °C.

14Komal tells you that she has a fever of 101 degrees. Does she mean it on the Celsius scale or Fahrenheit scale?

She means the Fahrenheit scale.

Human body temperature does not go above 42 °C. 101 °C is not possible. On the Fahrenheit scale, normal is 98.6 °F, so 101 °F means fever.

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