Page 34 - Science Class 07

Sir James Presco Joule, a 19th century
It shows that heat is transferred from one
Physicist, later proved that a given amount of
body to other.
mechanical energy always produces the same
amount of heat.

According to this theory, the heat that a body
possesses is directly related to the kine c
energy or energy of mo on of the molecules
composing the body. The greater the kine c
energy involved, the ho er the body is.

How Can We Define Cold?
Actually, there is no such things from the
TEMPERATURE
scien fic point of view. When we say that
object A is colder than object B, we mean that Temperature is a measure of the average heat
or thermal energy of the par cles in a
it has less heat. In other words, we can say that
substance. Since it is an average measurement,
all objects are hot at least amount of heat. To
it does not depend on the number of par cles
avoid confusion, we however use such words
in an object. In that sense, it does not depend
as “Cool”, “Cooler” and “Coolest” to indicate
on the size of it. For example, the temperature
certain degrees of heat.
of a small cup of boiling water is the same as
the temperature of a large pot of boiling water.

Even if the large pot is much bigger than the
cup and has millions and millions more water
Molecules of solids, gas or liquid stop molecules.
moving at the very low temperature called We experience temperature everyday. When it
absolute zero, equivalent to 273.160°
is very hot outside or when we have a fever, we
Celsius.
feel hot and when it is snowing outside, we feel
cold. When we are boiling water, we wait for the
water temperature to increase and when we
make popsicles, we wait for the liquid to
Aim : To show heat can be transferred from
one body to another. become very cold and freeze.

Method : Take one page of paper and a Scale of Temperature Measurement
piece of cloth. Keep the page on the piece of There are different scales for the measurement
cloth on a table. Now, switch on your electric of temperature. These are namely Celsius,
iron. When the iron gets heated press the Kelvin and Fahrenheit. The most widely used
paper using the iron for about 30 second. scale are the Farhrenheit (°F) and the Celsius
Now, remove the iron. (°C).
Touch the paper by one hand and the cloth
The Celsius Scale : In the Celsius scale, the
with the other. You will find that both the temperature at which pure ice melts at normal
things are hot.
atmospheric pressure is taken to be zero

34 Science-7