Heat is a form of energy that flows from hotter to colder objects. Temperature is a measure of how hot or cold an object is and is measured using a thermometer. A clinical thermometer specifically measures human body temperature, which is normally around 37°C, and works by having the user place the thermometer's mercury-filled bulb under their tongue for a minute to get a reading between 35-42°C.

1. Subject: Science
Class: 7th
Topic : Heat
Subtopic : Hot and cold, measuring temperature

2. How does the food gets
cooked?

3. Heat
 Heat is a form of energy which flows from a body at a higher temperature to a body at a
lower temperature. It is the form of energy which causes in us the sensation of hotness
or coldness.
 Heat always transfer from of higher temperature to the body of lower temperature or
heat flows spontaneously from hotter body to cooler body.

4. HOT AND COLD
 In our day-to-day life, we come across a
number of objects. Some of them are hot and
some of them are cold. E.g.-Tea is hot and ice
is cold.
 Some objects are hotter than others while some
are colder than others. We often decide which
object is hotter than the other by touching the
objects.

5.  We cannot always rely on our sense of
touch to decide how hot or how cold an
object is.
 When we add heat to body, motion of its
particle increase When we remove heat
from body, motion of its particle decrease.

6. How do we find out how hot an
object really is?
Temperature

7. TEMPERATURE
 Temperature is a measure of the degree of hotness or coldness of an object.
The temperature of something tells us how hot or cold something is.
 Temperature is measured by a device called thermometer.

8. Measuring Temperature
 Temperature is measured by a device called thermometer.
 Temperature is measured in degrees.
 Temperature is measured on two scales: Celsius and Fahrenheit.
 °C is the symbol for the Celsius scale. °F is the symbol for the
Fahrenheit scale

9.  The thermometer that measures our body temperature is called a clinical thermometer.
 A clinical thermometer consists of a long, narrow, uniform glass tube. It has a bulb at one end. This
bulb contains mercury. Outside the bulb, a small shining thread of mercury can be seen.
 A clinical thermometer reads temperature from 35°C to 42°C.

10. Reading on Thermometer
 First, note the temperature difference indicated
between the two bigger marks. Also note down the
number of divisions between these marks.
 Suppose the bigger marks read one degree and
there are five divisions between them. Then, one
small division can read 1/5=0.2°C.
 The normal temperature of human body is 37°C.
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11.  The temperature of every person may not be 37°C. It
could be slightly higher or slightly lower.
 The clinical thermometer is designed to measure the
temperature of human body only.
 The temperature of human body normally does not go
below 35 °C or above 42°C. That is the reason
that this thermometer has the range 35°C to 42°C.

12. How to use clinical thermometer
 Wash the thermometer with an antiseptic solution. Hold it firmly and give it a
few jerks to bring the level of mercury below 35 °C. Then place the bulb of the
thermometer under your tongue. After one minute take out the thermometer and
note the reading. This will be your body temperature.

13. Precautions to be observed while using a
clinical thermometer
 Thermometer should be washed before and
after use, preferably with an antiseptic solution.
 Ensure that before use the mercury level is
below 35°C.
 Read the thermometer keeping the level of
mercury along the line of sight.
 Handle the thermometer with care. If it hits
against some hard object, it can break.
 Don’t hold the thermometer by the bulb while
reading it.

14. Caution!!!
 Do not use a clinical thermometer for measuring the temperature of any object
other than the human body. Also avoid keeping the thermometer in the sun or
near a flame. It may break.

15. Questions?
Q) You may have noticed that a few sharp jerks are given to clinical
thermometer before using it. Why is it done so?
Answer:- The jerk will allow the mercury flow into the bulb above kink which will
make mercury level below normal temperature.

16. Questions?
Q)What is heat and temperature?
Answer-Temperature is the degree of hotness or coldness of a place or a
body. Heat Energy is the form of energy, which flows from a hot body to cold body.

17. Questions?
Q)What are the precautions while handling clinical thermometer?
Answer-
 Thermometer should be washed before and after use,
preferably with an antiseptic solution.
 Ensure that before use the mercury level is below
35°C.
 Read the thermometer keeping the level of mercury
along the line of sight.
 Handle the thermometer with care. If it hits against
some hard object, it can break.
 Don’t hold the thermometer by the bulb while reading
it.

18. Questions?
Q)What is the construction of clinical thermometer?
Answer -A clinical thermometer consists of a long, narrow,
uniform glass tube. It has a bulb at one end. This bulb
contains mercury. Outside the bulb, a small shining thread of
mercury can be seen. A clinical thermometer reads
temperature from 35°C to 42°C.

19. Summary
 Our sense of touch is not always a reliable guide to the degree of hotness of
an object.
 The heat flows from a body at a higher temperature to a body at a lower
temperature.
 Temperature is a measure of the degree of hotness of an object.
 Thermometer is a device used for measuring temperature.
 Clinical thermometer is used to measure our body temperature. The range
of this thermometer is from 35°C to 42°C.
 The normal temperature of the human body is 37°C.