Chapter

7 Temperature and
its Measurement

Wrong measurements are worse than

no measurements at all.
— Anna Mani

Lambok and his elder sister

Phiban live in Shillong. One day
they came home from school.
Their parents were away at
work and Lambok complained
that he was feeling feverish.
Phiban touched his forehead
and felt that he might be
having a fever. To confirm this,
she took out the thermometer
kept in the almirah. She
washed its tip with soap and
water, and measured Lambok’s
temperature. To her relief, she
found that his temperature
was normal. She washed the
thermometer tip again, dried

it and put it back. She then asked Can it always be

?
Lambok to change his school correctly judged, that
uniform, eat his lunch, and rest for a person has fever,
some time. only by touching the
person?
7.1 Hot or Cold?
We know from experience that some bodies are hotter than
others. For example, during summers, the tap water may be
hotter than the cold water from a matka (earthen pot) or a

Chapter 7.indd 123 10-07-2024 12:50:47

 refrigerator. We can realise this by merely touching the two
samples of water. But can we always rely upon our sense of
touch? Let us find out.

Activity 7.1: Let us investigate

‹‹ Take three large containers and label them A, B and C,
as shown in Fig. 7.1.
‹‹ Pour warm water in container A, tap water in B and ice-
cold water in C.
‹‹ We will conduct this activity in two parts — prediction
and observation.
‹‹ Firstly, predict what will you feel if you
—— dip your right hand in A and left hand in C and
keep them there for 1–2 minutes.
—— take out your hands from containers A and C, and
place both hands simultaneously in B.

A B C A B C
Curiosity | Textbook of Science| Grade 6

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

‹‹ Write down your predictions.

—— What will my right hand feel on dipping in B?

—— What will my left hand feel on dipping in B?

‹‹ Now, conduct the activity and write your observations.

124

Chapter 7.indd 124 10-07-2024 12:50:48

 Compare whether your observations match with your
predictions. Did your right hand feel that the water in
container B is cool, while your left hand felt that
the same water is warm? What do you infer
from these observations? Then how do we
find out how hot
We cannot always rely upon our sense of
or cold a body
touch to decide correctly whether a body is is?
hot or cold.

7.2 Temperature
A reliable measure of hotness (or coldness) of a body is
its temperature. A hotter body has a higher temperature
than a colder body. The difference in temperature between
the two bodies tells us how hot a body is in comparison to
another body. A device that measures temperature is called
a thermometer.
There are two kinds of thermometers that you are likely
to come across—clinical thermometers and laboratory
thermometers. Clinical thermometers are used to
measure human body temperatures whereas laboratory
thermometers are used for many other purposes. Let us
now learn more about thermometers and how to use them
to measure temperature.

7.3 Measuring Temperature

7.3.1 Clinical thermometer
You might be familiar with a thermometer, like that shown in
Fig. 7.2, which is used for measuring our body temperature.
It is called a clinical thermometer. Such thermometers show
Temperature and its Measurement

temperatures digitally. These are also known as digital

clinical thermometers and run on batteries. These measure

Tip
Fig.7.2: A digital clinical thermometer

125

Chapter 7.indd 125 10-07-2024 12:50:49

 temperature when the thermometer is placed in contact
with a person’s body.
For measuring temperature, the clinical thermometers
generally use a scale called the Celsius scale. On this
scale, the unit of temperature is degree Celsius and is
denoted by °C.

Earlier, mercury thermometers were used for measuring

the body temperature. But mercury is an extremely toxic
substance and is difficult to dispose of if the thermometer
breaks accidently.

Digital thermometers pose no such risk and also the

numbers in its display are easier to read. Therefore,
mercury thermometers are being replaced by digital
thermometers. Temperature in a digital thermometer
is determined with the help of heat sensors.

Dur Do you
pand ing the C know?
ther emic, so OVID-19
m me s
whic ometer
h co s we pecial
temp uld m re us
from e ra ture e a sure ed,
a dis o th
tanc f a pers e
e. on
thos What w
e? ere
Curiosity | Textbook of Science| Grade 6

They are non-contact thermometers,

also called infrared
thermometers. Such
thermometers can
measure temperature
without touching a
person’s body and
thus reduce the risk of
spreading disease.

126

Chapter 7.indd 126 10-07-2024 12:50:58

 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 Precautions
the temperature of some of your friends. to be taken while
Talk to your friends to find out who would using a digital clinical
be willing to get their body temperatures thermometer
measured by you. • To be used after reading the
‹‹ Wash your hands and the tip of the instruction manual of the
digital thermometer with soap and thermometer.
water. • Tip of the thermometer to
‹‹ Reset the thermometer by pressing the be washed with soap and
reset button. water before and after use.

‹‹ Place the thermometer under the • While washing, care to be

taken to keep the digital
tongue and close your mouth.
portion such as the display
‹‹ Wait till the thermometer makes a out of water.
beeping sound or flashes a light.
• Do not hold the thermometer
‹‹ Take it out from the mouth and read by the tip.
the temperature on the digital display.
‹‹ Record the temperature in Table 7.1.
‹‹ Clean the tip of the thermometer with soap and water,
and dry it.
‹‹ Repeat the above steps for measuring the temperatures
of your friends.

Table 7.1: Body temperatures of 10 persons Temperature and its Measurement

S. no. Name Temperature (°C)

10 127

Chapter 7.indd 127 10-07-2024 12:50:59

 The normal temperature of a healthy human body is taken
to be 37.0 °C. But in this activity, did you find that the normal
temperature of every person was 37.0 °C? Or did you find the
temperature slightly higher or lower for some people?
The temperature of every person may not
be 37.0 °C. What we call normal temperature

?
Do small children
is the average body temperature of a large
generally have number of healthy people. A perfectly
slightly higher body
healthy person may, therefore, have a
temperatures as
normal temperature slightly different from
compared to adults?
37.0 °C. The body temperature is influenced
by several factors, such as age, time of the
day and activity level.

?
Do old people, even You may try measuring your own
when healthy, generally temperature at different times of the day and
have lower body
on different days. Record the thermometer
temperatures than
readings in your notebook. After a month,
young adults?
analyse your temperature record and see if
there are any variations. If yes, try to think
what might be the reasons for that.
I have seen The temperature of human beings does
a friend of not normally go below 35 °C or above 42 °C.
using a dig m
ital thermo ine For measuring the body temperature
that reads meter
temperatu
a different re on of small children or old people, the digital
scale. It sh
the norma ows thermometer can also be placed in the
l temperatu
a healthy h re of armpit. The temperature measured this way
uman bod
98.6 °F. W y as
hat is the r
eason
is about 0.5 °C to 1 °C lower than the actual
for this diff body temperature.
erence?
There is another scale of temperature
Curiosity | Textbook of Science| Grade 6

known as Fahrenheit scale. On this scale, the

unit of temperature is degree Fahrenheit and
is denoted by °F. A temperature measured as
37.0 °C on Celsius scale is equivalent to 98.6 °F
on Fahrenheit scale. The Fahrenheit scale is
not used in most scientific studies anymore.
In scientific work, there is another scale of
temperature known as Kelvin scale. On this
scale, the unit for temperature is kelvin and
is denoted by K. The SI unit of temperature
128 is kelvin.

Chapter 7.indd 128 10-07-2024 12:50:59

 All three temperature We can easily convert the
scales, Celsius, Fahrenheit temperature from Celsius scale to
and Kelvin are named in Kelvin scale by using:
honour of the scientists who
Temperature in Kelvin
developed these scales.
scale = Temperature in
Celsius scale + 273.15

More to
The names of temperature scales—Celsius
scale,
know!
Fahrenheit scale and Kelvin scale—start
with a capital
letter. For the units for temperature, deg
ree Celsius and degree
Fahrenheit, the word degree starts with
a lower-case letter while
Celsius and Fahrenheit start with a capital
letter. The unit kelvin
starts with a lower-case letter. The symbols
of all units (°C, °F, K) are
capital letters. Note that degree sign (°) is
not written with K. A full
stop is not written after the symbol, except
at the end of a sentence.
While writing the temperature, a space is
left between the number
and the unit. For temperatures more than
one degree, use the plural
of ‘degree’, that is, ‘degrees’, while writing
the full form of the unit.

How was fever detected before

?
? Fever
Can a clinical thermometers were developed
. This
thermometer be affects the pulse rate of a person
used for measuring was known even in olden days
the temperature of in India. However, apart from
boiling water? Or fever, some other situations
for measuring the also affect the pulse rate.
temperature of ice?
Hence, pulse rate alone is not
Temperature and its Measurement

Do you a reliable indicator of fever.

know?
No, the
temperatures of
boiling water and
ice are outside the How can we measure
range of a clinical temperatures beyond
thermometer. the range of a clinical
thermometer?

129

Chapter 7.indd 129 10-07-2024 12:51:41

 7.3.2 Laboratory thermometer
There are many types of laboratory thermometers but the
one that might be available in your school laboratory may
look like the one shown in Fig. 7.3a. It consists of a long,
narrow, uniform glass tube which is sealed. At one end of
the tube is a bulb which contains a liquid. Outside the bulb,
in the tube, a narrow column of liquid can be seen. There
is a Celsius scale marked along the tube. The liquid column
rises or falls with change in temperature. The mark of the
Celsius scale with which the top level of the liquid column
coincides is the temperature reading.

The liquid used in the laboratory

thermometer is generally alcohol (coloured
red to make it easily seen) or mercury. Do you
know?

Activity 7.3: Let us observe

Let us try to find the temperature range of a given laboratory
thermometer.
‹‹ Take a laboratory
thermometer and observe it
carefully. Precautions
‹‹ Note down the following: to be taken while
using a laboratory
—— What is the lowest thermometer
temperature it
Curiosity | Textbook of Science| Grade 6

• Handle with care. If

can measure?
it hits against some
Bulb
hard object, it can
—— What is the highest break.
temperature it • Do not hold it by the
can measure? bulb.
Fig.7.3(a):
A laboratory —— So, the range of this
thermometer thermometer is
Now look at the thermometer shown in Fig. 7.3a carefully.
Can you tell its range? Its range is from –10 °C to 110 °C.
130

Chapter 7.indd 130 10-07-2024 12:51:59

 Activity 7.4: Let us observe and calculate
Let us now try to find the smallest value that a given
laboratory thermometer can read.
‹‹ Again, take the same laboratory thermometer which
you used in Activity 7.3 and observe it carefully.
‹‹ Note down the following:
—— How much is the temperature difference indicated
between the two bigger marks?
—— How many divisions (shown by smaller marks)
are there between these two bigger marks?

—— How much temperature does one small division

indicate?
—— So, the smallest value that the thermometer can
read is
Fig. 7.3b shows a closeup of a part of the thermometer
shown in Fig. 7.3a. Can you now find the smallest value that
this thermometer can read?
For the thermometer shown in Fig. 7.3b, the
temperature difference indicated between 0 °C and
10 °C or between 10 °C and 20 °C is 10 °C. And the
number of divisions between these marks are 10
divisions. So, one small division can read 10/10 = 1 °C.
That is, the smallest value that this thermometer
can read is 1 °C.
Your school laboratory may have thermometers for
which the range and the value of the smallest division
Temperature and its Measurement

may be different. It is, therefore, always necessary to

look carefully at the thermometer you are about to use.
You have learnt how to find the temperature
range of a given laboratory thermometer. You have
also learnt how to find the smallest value that
Fig. 7.3(b):
a given laboratory thermometer can read. We
Closeup of a will now learn how to measure temperature
part of the using a laboratory thermometer. But, let us first
thermometer learn how to use a laboratory thermometer
shown in
Fig. 7.3a.
correctly. 131

Chapter 7.indd 131 10-07-2024 12:51:59

 Correct way of measuring temperature using a
laboratory thermometer
‹‹  hen the thermometer
W
is immersed in water, its
bulb should not touch
the bottom or the sides
of the beaker.
‹‹ The thermometer
should be held
vertically (Fig. 7.4). It
Closeup of a part of
laboratory thermometer should not be tilted.

Laboratory thermometer
‹‹ The temperature
must be read while
Beaker
the thermometer is
Warm water
immersed in water.
Fig.7.4: Measuring temperature of warm water ‹‹ 
W hile reading the
thermometer, the eye
should be directly in line with the level of the liquid column
to be read (Fig. 7.4).

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 (Fig. 7.4).
‹‹ Observe the rise of liquid column in the thermometer.
Wait till the column stops rising and note the
Curiosity | Textbook of Science| Grade 6

Can se temperature (do not wait too long; otherwise,

u y
we rator for the water itself will start to cool).
bo ter What is the temperature of water
a la ome body
rm ng fa measured by you? Compare it with the
the asuri ure o
me perat n? readings of your friends.
o
tem pers Do you notice that, as soon as you take the
thermometer out of the water, the level of liquid
column begins to fall?
This means that the temperature must be read
while the thermometer is immersed in water.
132

Chapter 7.indd 132 10-07-2024 12:52:00

 Following two experimental setups are to be arranged by your
teacher. One by one, as per your turn, go closer to the setups
and observe the readings of both the thermometers. What are
the temperatures of ice and boiling water? More to
do!

Laboratory
thermometer

Boiling
Laboratory water
thermometer
Burner
Crushed ice Caution
This activit
y
should be
performed
strictly
Read the temperatures of ice and boiling water again after only unde
r
supervisio
some time. Are the temperatures same or have changed? You n of
the teache
may have noticed that the temperature of water remains r. Do
not touch
constant while it is boiling. Also, the temperature of ice the
experimen
remains constant while it is melting. tal
setups.

Activity 7.6: Let us compare

‹‹ Phiban’s Science teacher arranged the experimental
setup for measuring temperature of boiling water. The
temperature readings of the boiling water taken by Phiban
and her classmates in Shillong are given in Table 7.2.
Table 7.2: Temperature of boiling water
Temperature and its Measurement

Temperature of boiling
Name water (in °C)

Phiban 97.8

Shemphang 98.0

Onestar 97.9

Kloi 98.0

Bandarisha 98.1
133

Chapter 7.indd 133 10-07-2024 12:52:15

 ‹‹ Compare the temperatures of boiling water recorded by
different students.
Why are there differences in their readings? Discuss the
possible reasons amongst yourselves. Maybe, the correct way
of reading temperature was not followed by all the students.

7.3.3 Air temperature

You might have seen thermometers,
such as the one shown in Fig. 7.5, hung
on walls of your school laboratory,
doctor’s clinic, and hospitals. These
give an approximate idea of the
room temperature.
Have you seen weather reports
in newspapers, TV news or internet?
These reports also mention the
maximum and minimum air
temperature of the day.

Fig.7.5: Room thermometer

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 in the Table 7.3.
Curiosity | Textbook of Science| Grade 6

Table 7.3: Maximum and minimum air temperature

Maximum air Minimum air

S.no. Date
temperature temperature

1.

134 10.

Chapter 7.indd 134 10-07-2024 12:52:16

 Does the maximum and minimum temperature stay at
the same level during these days?
Because weather depends on several factors, these
temperatures usually vary every day. Generally, as we
approach the summer season, the temperature rises and
during the winter season it falls.

There are many techniques for measuring

air temperature. Air temperature is an
important weather parameter and is
More to
monitored at weather stations all over
know!
the world. The data gathered on air
temperature along with various other
parameters are used for making weather
forecasts.

Anna Mani (1918–2001)

was an Indian scientist,
also known as the ‘Weather
Woman of India’. She
invented and built a
large number of weather
measurement instruments.
Temperature and its Measurement

This reduced the reliance of

India on other nations for
such instruments. She also
explored the possibilities
of using wind and solar
energy in India. Her work
helped India to become
one of the global leaders in
renewable energy.
135

Chapter 7.indd 135 10-07-2024 12:52:30

 Keywords

Air Temperature Analyse

Celsius Scale Calculate

Clinical thermometer Compare

degree Celsius Discuss

degree Fahrenheit Infer

Fahrenheit scale Investigate

kelvin Measure

Kelvin scale Observe

Laboratory thermometer Precaution

SI unit of temperature Predict

Temperature Record

Summary
Curiosity | Textbook of Science| Grade 6

‹‹ The temperature of a body tells us how hot or cold it is.

‹‹ The three most-used scales of temperature are: (a) the Celsius
scale, (b) the Fahrenheit scale, and (c) the Kelvin scale. The units
of temperature in these scales are (a) degree Celsius, denoted by °C,
(b) degree Fahrenheit, denoted by °F, and (c) kelvin, denoted by K.
‹‹ The SI unit for 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
136 from –10 °C to 110 °C.

Chapter 7.indd 136 10-07-2024 12:52:36

 Let us enhance our learning

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
2. 37 °C is the same temperature as .
(i) 97.4 °F
(ii) 97.6 °F
(iii) 98.4 °F
(iv) 98.6 °F
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 .
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
5. Four students used a laboratory thermometer to measure
the temperature of water as shown in Fig. 7.6:
Temperature and its Measurement

Student 1 Student 2 Student 3 Student 4

137
Fig. 7.6

Chapter 7.indd 137 10-07-2024 12:52:40

 Who do you think followed the correct way for measuring
temperature?
(i) Student 1
(ii) Student 2
(iii) Student 3
(iv) Student 4
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

Fig. 7.7

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

answer the following questions:
Curiosity | Textbook of Science| Grade 6

Fig. 7.8

(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?
8. A laboratory thermometer is not used to measure our body
temperature. Give a reason.
138

Chapter 7.indd 138 10-07-2024 12:52:42

 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.
Table 7.4: Body temperature record of Vaishnavi

Temperature at

DAY 7am 10am 1pm 4pm 7pm 10pm

One 38.0 °C 37.8 °C 38.0 °C 38.0 °C 40.0 °C 39.0 °C

Two 38.6 °C 38.8 °C 39.0 °C 39.0 °C 39.0 °C 38.0 °C

Three 37.6 °C 37.4 °C 37.2 °C 37.0 °C 36.8 °C 36.6 °C

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

(ii) On which day and at what time was Vaishnavi’s highest
temperature recorded?
(iii) On which day did Vaishnavi’s temperature return to
normal?
10. If you have to measure the temperature 22.5 °C, which of
the following three thermometers will you use (Fig. 7.9)?
Explain.

Temperature and its Measurement

(a) (b) (c)

Fig. 7.9: Three thermometers

139

Chapter 7.indd 139 10-07-2024 12:52:43

 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 Fig. 7.10

12. A laboratory thermometer has 50 divisions between 0 °C

and 100 °C. What does each division of this thermometer
measure?
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.
14. Someone tells you that she has a fever of 101 degrees. Does
she mean it on the Celsius scale or Fahrenheit scale?

Learning further

‹‹ 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.
‹‹ 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.
‹‹ Various planets in our Solar System are at different distances
Curiosity | Textbook of Science| Grade 6

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.
‹‹ 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.
140

Chapter 7.indd 140 10-07-2024 12:52:48

 Record your readings. Compare the readings and draw
your conclusions. Repeat this for two weeks.

Thermometer 1
(Room thermometer)

Thermometer 2
(Laboratory thermometer)

Beaker
Water

Fig. 7.11: Set up to measure temperature of water and room temperature

The temperature at the core of the Sun reaches

as high as 15 million degrees Celsius. Are
More to there objects in the sky that have even higher
know! temperatures? There is no limit on the highest
temperature that can exist. However, as per
Temperature and its Measurement

scientific understanding, there is a limit to the

lowest temperature that can be achieved. It
is close to –273.15 °C (0 kelvin) and is called
absolute zero.

141

Chapter 7.indd 141 10-07-2024 12:53:05

 Notes

Chapter 7.indd 142 10-07-2024 12:53:05