This document discusses heat, temperature, and how they are measured. It explains that temperature is a property that indicates whether an object is hot or cold, and is measured using a thermometer. A higher temperature means an object is hotter, while a lower temperature means it is colder. While our sense of touch can determine relative hotness and coldness, temperature measured with a thermometer provides an exact reading in degrees Celsius. The document also describes physical and chemical changes that occur in objects when heat is added or removed.

1. HOT AND COLD
TEMPERATURE
Suman Kumar Krishna
Integrated B.Sc. B.Ed. (Medical)

2. • Heat is form of energy flowing from one body of
matter to another spontaneously due to their
temperature difference.
• When a hot object and a cold object come in
contact with each other, a type of energy flows
from the hot object to the colder one. This energy
is called heat energy.

3. Heat is a form of energy which makes the substance hot. In winter, it is our
common experience that we feel cold inside the house and if we come out in
front of sun rays, then we feel warm.
Now, if we know that how do we feel this
sensation of warm or cold? Then, what will be
our answer? Think.
In this lesson, we will try to find out the answer to such
kind of question.

4. • In our daily routine, we come across a number of objects, out of which
some are hot while other objects are cold, e.g. when a frying pan kept
on a burning gas stove becomes hot but the handle of the pan is cold.
• Even among the hot objects, some objects may be hotter than the other.
In the same manner, among the cold objects, some objects may be
colder than the other.
• So, if I ask you how you decide the relative hotness or coldness of
objects, then your answer will be ’by simply touching the objects’.

5. Our sense of touch is
not enough in telling us
whether an object is
really hot or cold so,
this can be understood
by performing a simple
activity.

6. • The degree of hotness or coldness of the object is known as the
temperature of an object.
• The temperature of an object is an only property that indicates
which object is hot and which one is cold.
• A high temperature of a body indicates that it is very hot whereas a
low temperature of the object indicates that it is quite cold, e.g. the
temperature of boiling water is quite high, so boiling water appears
to be very hot.
• On the other side, the temperature of melting ice is quite low. So, ice
appears to be very cold on touch.
Temperature

7. • It is measured by using an instrument called thermometer, which
has a scale marked on it which is used to read the temperature,
e.g. the scale in laboratory thermometer is marked along the
length of thermometer’s tube between 0° mark and 100° mark into
100 equal divisions.
• So, each division is called a degree. The temperature of an object
should always be stated with its unit.
• So, the most common unit for measuring temperature is degree
Celsius (°C).
Thermometer

8. EFFECT OF HEAT
When body is heated various types of physical & chemical change take place.
• PHYSICAL CHANGES
• a) CHANGE IN TEMPERATURE On adding heat to body, its temperature
increase. On removal of heat from body, its temperature decrease.
• b) CHANGE OF STATE On addition or removal of heat to/from body, there is
change in state of body. Ex- change of ice to water on addition of heat etc.
• c) THERMAL EXPANSION The phenomenon of expansion of matter on
heating is called thermal expansion.
• CHEMICAL CHANGES On heating reactant , many case chemical changes
take place.

9. • What would happen if we have only
winter season on earth?
• What would happen if we are not able
to differentiate between hot and cold
temperatures?
• What would happen if there is no
device to measure the temperature?

10. Choose the Correct Option:
Which of the following is odd one out?
a. coffee
b. tea
c. soup
d. ice cream

11. State True or False:
• The hotness of an object is determined by its
temperature. [True/ False].
• Temperature is measured by a device called thermometer.
[True/ False].

12. So, today we have learnt about ‘Hot and Cold
Temperatures’ and now let’s summarize today’s class:
What is thermometer?
What are two types temperature?
Explain why human senses are not trustworthy
sometimes.
Name two places where we use clinical thermometer?

13. Homework
• Go to a doctor or your nearest health center. Observe the
doctor taking temperature of patients. Enquire:
(a)why she dips the thermometer in a liquid before use.
(b)why the thermometer is kept under the tongue.
(c) whether the body temperature can be measured by
keeping the thermometer at some place other than the
mouth.
(d)whether the temperature of different parts of the body is
the same or different.
You can add more questions which come to your mind.