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Class 6 Science Chapter 7 – Temperature and Its Measurement | Notes, Solutions & Worksheet

Class 6 Science Chapter 7 Temperature and Its Measurement – easy notes, concepts, NCERT book solutions, important questions, worksheet and answers. Learn about temperature, measuring temperature, thermometers, units of temperature and safe ways to measure temperature in simple language.

Class 6 Science

Chapter 7: Temperature and its Measurement

Easy Notes • Important Concepts • Textbook Questions & Solutions

Chapter at a Glance

In this chapter, we learn how to measure temperature correctly. We understand why our sense of touch is not always reliable, what temperature means, and how to use clinical, laboratory and room thermometers. We also learn about Celsius, Fahrenheit and Kelvin scales, thermometer readings, temperature ranges and correct precautions while measuring temperature.

1. Hot or Cold?

Can we judge temperature only by touching?

No. Our sense of touch can sometimes give us a wrong idea about whether something is hot or cold.

A thermometer gives us a more reliable measurement of temperature.

Can it always be correctly judged, that a person has fever, only by touching the person?
Answer: No. Fever cannot be judged correctly only by touching a person. A thermometer should be used to measure the temperature.

Activity 7.1: Let us investigate

Take three large containers and label them A, B and C. Put warm water in A, tap water in B and ice-cold water in C.

A Warm water B Tap water C Ice-cold water

Fig. 7.1: Feeling hotness or coldness of water by dipping hands

If one hand is first placed in warm water and the other in ice-cold water, then both hands may feel the same tap water differently.

Conclusion: We cannot always rely upon our sense of touch to decide correctly whether a body is hot or cold.

2. Temperature

What is temperature?

Temperature is a reliable measure of how hot or cold a body is.

A hotter body has a higher temperature than a colder body.

What is a thermometer?

A thermometer is a device used to measure temperature.

Clinical Thermometer

Used mainly to measure human body temperature.

Laboratory Thermometer

Used to measure the temperature of substances during experiments.

3. Measuring Temperature

3.1 Clinical Thermometer

A clinical thermometer is used for measuring our body temperature. Digital clinical thermometers show the temperature on a digital display and run on batteries.

37.0°CDigital display Tip / sensor Button Battery

Fig. 7.2: A digital clinical thermometer

Celsius Scale

Clinical thermometers generally use the Celsius scale. The unit is degree Celsius and its symbol is °C.

Digital Thermometers

Earlier, mercury thermometers were commonly used for measuring body temperature. Mercury is toxic, so digital thermometers are safer and easier to read.

Non-contact Thermometers

Infrared thermometers can measure temperature without touching the person’s body. They were especially useful during the COVID-19 pandemic.

During the COVID-19 pandemic, some special thermometers were used, which could measure the temperature of a person from a distance. What were those?
Answer: They were non-contact or infrared thermometers.

Activity 7.2: Let us measure

Let us now use a digital clinical thermometer to measure body temperature. You may measure your own temperature as well as the temperature of some of your friends.

Steps

  1. Wash your hands and the tip of the digital thermometer with soap and water.
  2. Reset the thermometer by pressing the reset button.
  3. Place the thermometer under the tongue and close your mouth.
  4. Wait till the thermometer makes a beeping sound or flashes a light.
  5. Take it out from the mouth and read the temperature on the digital display.
  6. Record the temperature in Table 7.1.
  7. Clean the tip of the thermometer with soap and water, and dry it.
  8. Repeat the above steps for measuring the temperatures of your friends.

Table 7.1: Body temperatures of 10 persons

S. no.NameTemperature (°C)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.

Precautions to be taken while using a digital clinical thermometer

  • Use it after reading the instruction manual.
  • Wash the tip with soap and water before and after use.
  • Keep the digital portion such as the display away from water.
  • Do not hold the thermometer by the tip.

4. Normal Body Temperature

Normal temperature of a healthy human body = 37.0 °C = 98.6 °F

The temperature of every healthy person may not be exactly 37.0 °C. The normal temperature is an average value. Body temperature can change with age, time of day and activity level.

Do small children generally have slightly higher body temperatures as compared to adults?
Answer: Body temperature can vary with age, and small children may have slightly different normal temperatures.
Do old people, even when healthy, generally have lower body temperatures than young adults?
Answer: Body temperature can vary with age. Healthy older people may have slightly different normal temperatures.
I have seen a friend of mine using a digital thermometer that reads temperature on a different scale. It shows the normal temperature of a healthy human body as 98.6 °F. What is the reason for this difference?
Answer: The thermometer is showing the temperature on the Fahrenheit scale. 37.0 °C is equal to 98.6 °F.

The human body normally does not have a temperature below 35 °C or above 42 °C.

Temperature in the Armpit

For small children or old people, a digital thermometer may also be placed in the armpit. The reading obtained this way is usually about 0.5 °C to 1 °C lower than the actual body temperature.

5. Temperature Scales

Celsius Scale

Unit: degree Celsius

Symbol: °C

Fahrenheit Scale

Unit: degree Fahrenheit

Symbol: °F

Kelvin Scale

Unit: kelvin

Symbol: K

SI Unit

The SI unit of temperature is kelvin (K).

Temperature in Kelvin scale = Temperature in Celsius scale + 273.15

Therefore, 37.0 °C = 310.15 K.

Writing temperature correctly:
  • Write °C for degree Celsius.
  • Write °F for degree Fahrenheit.
  • Write K for kelvin.
  • Do not write the degree sign with K.
  • Leave a space between the number and the unit, for example 37.0 °C.

More to know

Celsius scale, Fahrenheit scale and Kelvin scale are named in honour of the scientists associated with their development.

How was fever detected before thermometers were developed?
Answer: Fever was sometimes judged using pulse rate and other signs. However, pulse rate alone is not a reliable indicator of fever.
Can a clinical thermometer be used for measuring the temperature of boiling water? Or for measuring the temperature of ice?
Answer: No. The temperatures of boiling water and ice are outside the suitable range of a clinical thermometer.
How can we measure temperatures beyond the range of a clinical thermometer?
Answer: We can use a suitable laboratory thermometer or another thermometer designed for that temperature range.

6. Laboratory Thermometer

A laboratory thermometer has a long, narrow glass tube and a bulb containing a liquid. It has a Celsius scale. The liquid column rises or falls when the temperature changes.

110 °C 80 °C 50 °C 20 °C -10 °CBulb Liquid column

Fig. 7.3: Laboratory thermometer — simplified diagram

Typical range: –10 °C to 110 °C

Activity 7.3: Let us observe

Take a laboratory thermometer and observe it carefully.

  • What is the lowest temperature it can measure?
  • What is the highest temperature it can measure?
  • So, the range of this thermometer is ______.
Answer for the thermometer shown in the textbook: Its range is from –10 °C to 110 °C.

Activity 7.4: Let us observe and calculate

Let us now try to find the smallest value that a given laboratory thermometer can read.

How to find the smallest division

First find the temperature difference between two bigger marks. Then count the number of small divisions between them.

Value of one small division = Temperature difference ÷ Number of divisions

For the thermometer shown in the textbook, the difference between 0 °C and 10 °C is 10 °C and there are 10 divisions.

Therefore: 10 ÷ 10 = 1 °C

So the smallest value that this thermometer can read is 1 °C.

7. Correct Way of Using a Laboratory Thermometer

Warm water in beakerThermometer held vertically Bulb immersed in water Bulb does not touch bottom or sides

Fig. 7.4: Measuring temperature of warm water

Important rules

  • The bulb should be immersed in the water.
  • The bulb should not touch the bottom or sides of the beaker.
  • The thermometer should be held vertically.
  • The temperature should be read while the thermometer is still immersed.
  • The eye should be directly in line with the level of the liquid column.

Activity 7.5: Let us measure

Take some warm water in a beaker. Dip the thermometer in water so that the bulb is immersed in water. Observe the rise of liquid column in the thermometer. Wait till the column stops rising and note the temperature.

Can we use a laboratory thermometer for measuring body temperature of a person?
Answer: No. A laboratory thermometer is not designed for measuring human body temperature. A clinical thermometer should be used for this purpose.

Activity 7.6: Let us compare

NameTemperature of boiling water (in °C)
Phiban97.8
Shemphang98.0
Onestar97.9
Kloi98.0
Bandarisha98.1
Why are there differences in their readings? Discuss the possible reasons amongst yourselves.
Answer: Small differences may happen because the thermometer may not have been positioned correctly, the reading may have been taken differently, or the eye may not have been at the correct level.

Caution

Experiments involving boiling water and burners should be performed strictly under the supervision of the teacher. Do not touch the experimental setups.

What are the temperatures of ice and boiling water?
Answer: Under standard conditions, melting ice is about 0 °C and boiling water is about 100 °C.
Read the temperatures of ice and boiling water again after some time. Are the temperatures same or have changed?
Answer: While ice is melting and water is boiling, the temperature remains nearly constant under the same conditions.

8. Air Temperature

Room Thermometer

Room thermometers give an approximate idea of room temperature. They may be found in schools, hospitals, clinics and other places.

40 °C 30 °C 20 °C 10 °C Room thermometer

Fig. 7.5: Room thermometer — simplified diagram

Activity 7.7: Let us analyse

Read or listen to the weather reports for a place for 10 successive days. Record the maximum and minimum air temperature for each day in Table 7.3. Analyse the data.

S.no.DateMaximum air temperatureMinimum air temperature
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Does the maximum and minimum temperature stay at the same level during these days?
Answer: No. They usually change from day to day because weather depends on several factors.

Weather and Temperature

Air temperature is an important weather parameter. Weather stations measure air temperature and other weather conditions to help prepare weather forecasts.

More to know: Anna Mani

Anna Mani (1918–2001) was an Indian scientist, also known as the “Weather Woman of India”. She worked on weather measurement instruments and explored wind and solar energy.

9. Summary

  • The temperature of a body tells us how hot or cold it is.
  • The three most-used scales of temperature are Celsius, Fahrenheit and Kelvin.
  • The units are degree Celsius (°C), degree Fahrenheit (°F) and kelvin (K).
  • The SI unit of temperature is kelvin.
  • A clinical thermometer is used for measuring body temperature.
  • Normal temperature of a healthy human adult is taken to be 37.0 °C or 98.6 °F.
  • Laboratory thermometers typically have a temperature range from –10 °C to 110 °C.

10. Keywords

Analyse Investigate Discuss Compare Infer Measure Observe Precaution Kelvin Air Temperature Degree Fahrenheit Kelvin scale Clinical thermometer Celsius Scale Degree Celsius Fahrenheit scale Laboratory thermometer Temperature Predict Record SI unit of temperature Calculate

11. Let Us Enhance Our Learning – Textbook Solutions

Question 1

1. The normal temperature of a healthy human being is close to .
(i) 98.6 °C
(ii) 37.0 °C
(iii) 32.0 °C
(iv) 27.0 °C
Answer: (ii) 37.0 °C
The normal temperature of a healthy human being is taken to be about 37.0 °C.

Question 2

2. 37 °C is the same temperature as .
(i) 97.4 °F
(ii) 97.6 °F
(iii) 98.4 °F
(iv) 98.6 °F
Answer: (iv) 98.6 °F
37 °C is equal to 98.6 °F.

Question 3

3. Fill in the blanks:
(i) The hotness or coldness of a system is determined by its .
(ii) The temperature of ice-cold water cannot be measured by a thermometer.
(iii) The unit of temperature is degree .
Answers:
(i) temperature
(ii) clinical
(iii) Celsius

Question 4

4. The range of a laboratory thermometer is usually .
(i) 10 °C to 100 °C
(ii) –10 °C to 110 °C
(iii) 32 °C to 45 °C
(iv) 35 °C to 42 °C
Answer: (ii) –10 °C to 110 °C
A laboratory thermometer has a wider range and can measure temperatures from about –10 °C to 110 °C.

Question 5

5. Four students used a laboratory thermometer to measure the temperature of water as shown in Fig. 7.6:

Who do you think followed the correct way for measuring temperature?
(i) Student 1
(ii) Student 2
(iii) Student 3
(iv) Student 4
Student 1 Bulb touches bottom Student 2 Correct method Student 3 Thermometer tilted Student 4 Bulb not properly immersed

Fig. 7.6: Simplified illustration of the four methods

Answer: (ii) Student 2
Student 2 follows the correct method. The thermometer is held vertically, the bulb is immersed in water and it does not touch the sides or bottom.

Question 6

6. Colour to show the red column on the drawings of thermometers (Fig. 7.7) as per the temperatures written below:

14 °C     17 °C     7.5 °C
Answer:
For 14 °C, colour the liquid column up to the 14 °C mark.
For 17 °C, colour the liquid column up to the 17 °C mark.
For 7.5 °C, colour the liquid column halfway between 7 °C and 8 °C.

Question 7

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

(i) What type of thermometer is it?
(ii) What is the reading of the thermometer?
(iii) What is the smallest value that this thermometer can measure?
(i) Answer: It is a clinical thermometer.

(ii) Answer: The reading is 26 °C.

(iii) Answer: The smallest value is -10 °C.

Question 8

8. A laboratory thermometer is not used to measure our body temperature. Give a reason.
Answer: A laboratory thermometer is designed for laboratory experiments and has no suitable arrangement for safely retaining a body-temperature reading. A clinical thermometer is designed for measuring body temperature.

Question 9

9. Vaishnavi has not gone to school as she is ill. Her mother has kept a record of her body temperature for three days as shown in Table 7.4.
DAY7am10am1pm4pm7pm10pm
One38.0 °C37.8 °C38.0 °C38.0 °C40.0 °C39.0 °C
Two38.6 °C38.8 °C39.0 °C39.0 °C39.0 °C38.0 °C
Three37.6 °C37.4 °C37.2 °C37.0 °C36.8 °C36.6 °C

(i) What was Vaishnavi’s highest recorded temperature?

Answer: Vaishnavi’s highest recorded temperature was 40.0 °C.

(ii) On which day and at what time was Vaishnavi’s highest temperature recorded?

Answer: It was recorded on Day One at 7 pm.

(iii) On which day did Vaishnavi’s temperature return to normal?

Answer: Her temperature returned to normal on Day Three, when it reached 37.0 °C at 4 pm.

Question 10

10. If you have to measure the temperature 22.5 °C, which of the following three thermometers will you use (Fig. 7.9)? Explain.
Answer: Thermometer (b)
A temperature of 22.5 °C needs a thermometer that can measure 0.5 °C differences. Thermometer (b) has the required smaller divisions.

Question 11

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

(i) 28.0 °C
(ii) 27.5 °C
(iii) 26.5 °C
(iv) 25.3 °C
Answer: (ii) 27.5 °C
The liquid level shown in the figure corresponds to 27.5 °C.

Question 12

12. A laboratory thermometer has 50 divisions between 0 °C and 100 °C. What does each division of this thermometer measure?
Solution:
Temperature difference = 100 °C − 0 °C = 100 °C
Number of divisions = 50

100 ÷ 50 = 2 °C

Answer: Each division measures 2 °C.

Question 13

13. Draw the scale of a thermometer in which the smallest division reads 0.5 °C. You may draw only the portion between 10 °C and 20 °C.
Answer: Divide every 1 °C interval into two equal parts. Each small division will then represent 0.5 °C.

Question 14

14. Komal tells you that she has a fever of 101 degrees. Does she mean it on the Celsius scale or Fahrenheit scale?
Answer: She most likely means 101 °F. A body temperature of 101 °C is impossible for a human body.

12. Learning Further

Activity 1: Body Temperature of Animals

Gather information from the Internet and find out how the body temperature of animals, such as a cat, dog, horse, camel, cow and buffalo is measured. If there is any veterinary hospital in your vicinity, you may visit to see the body temperature of animals being measured.
Suggested answer:
The body temperature of animals is generally measured using a suitable digital veterinary thermometer. The thermometer is used according to the animal and the instructions given by the veterinarian.

Activity 2: Coldest and Hottest Places in India

Find out which places in India are usually regarded to be the coldest and hottest. Also, find out the minimum and the maximum temperatures recorded for these places.
Suggested activity:
Use a reliable weather or government source and prepare a table containing:

Place | Minimum temperature | Maximum temperature | Source

Students should record the date and source because temperature records can change with time.

Activity 3: Temperatures of Planets

Various planets in our Solar System are at different distances from the Sun. Search the Internet and make a table with the planets, their distances from the Sun (in increasing order) and their temperatures written. Does the average temperature of planets decrease as their distance from the Sun increases? If it is not true for any planet, find out for which planet and why.
Suggested answer:
Generally, planets farther from the Sun receive less solar energy, but distance from the Sun is not the only factor affecting temperature. For example, a planet’s atmosphere can strongly affect its temperature.

Activity 4: Measuring Water and Room Temperature

Hang a room thermometer in your classroom. Set up the apparatus, as shown in Fig. 7.11, near the thermometer hung on the wall. Take the readings of thermometers 1 and 2 three times during the day, say, first period, lunch break, and last period. Record your readings. Compare the readings and draw your conclusions. Repeat this for two weeks.
TimeThermometer 1: Room temperatureThermometer 2: Water temperatureObservation
First period
Lunch break
Last period

13. More to Know

The temperature at the core of the Sun reaches as high as 15 million degrees Celsius.

There is a limit to how low temperature can go. The lowest possible temperature is close to –273.15 °C, which is called absolute zero.

Absolute zero is equal to approximately 0 kelvin.

14. Quick Concept Revision

ConceptEasy Meaning
TemperatureA measure of how hot or cold a body is.
ThermometerAn instrument used to measure temperature.
Clinical thermometerUsed mainly to measure body temperature.
Laboratory thermometerUsed for measuring temperatures during experiments.
CelsiusA commonly used temperature scale with symbol °C.
FahrenheitA temperature scale with symbol °F.
KelvinThe SI unit of temperature; symbol K.
Temperature rangeThe lowest to highest temperature a thermometer can measure.
Smallest divisionThe smallest temperature value that a thermometer can read.
Air temperatureThe temperature of the surrounding air.

15. Important Formulas

One small division = Temperature difference ÷ Number of divisions
Kelvin temperature = Celsius temperature + 273.15
37.0 °C = 98.6 °F

16. Important Precautions

17. One-Page Memory Map

TEMPERATURE Thermometers Temperature Scales Measurement Clinical Laboratory Celsius Fahrenheit Kelvin Range Smallest division Measure correctly = Accurate result
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Class 6 Science • Chapter 7: Temperature and its Measurement
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