by Dilip Kumar Chandra PGT Biotechnology JNV Raipur CG

2. • Heat is energy transferred from one
system to another by thermal interaction.
.
Heat is transported to Earth as electromagnetic radiation
from sun This is the main source of energy for life on
Earth

3. • Our sense of touch is not always a reliable
guide to the degree of hotness of an
object.
Cold water in mug `A Hot water in mug `B Cold and hot water mixed in `C
EXPERIMENT

4. Our sense of touch is not always a
reliable guide to the degree of
hotness of an object.
• Take cold water in mug A ,hot water in
mug B and mix cold and hot water in mug
`C .Now dip your left hand in mug A and
right hand in mug B .Now put both the
hands simultaneously in mug C .Do both
the hands get the same feeling…..discuss.

5. MEASUREMENT OF TEMPERATURE
• Degree of hotness is called temperature.
• Temperature is measured by a device
called Thermometer.

6. MEASUREMENT OF TEMPERATURE
• The Thermometer that measures our body
temperature is called clinical thermometer,

7. Clinical Thermometer
4
1
2
5
3
5

8. MEASUREMENT OF TEMPERATURE
• The Thermometer that measures
temperatures in laboratory is called
laboratory thermometer,

9. MEASUREMENT OF TEMPERATURE
• Laboratory thermometer:
Do you notice that as soon as you take the
thermometer out of water, the level of mercury
begins to fall.
This means that the temperature must be read
while the thermometer is in water.

10. MEASUREMENT OF TEMPERATURE
• Think out:
• Can we use laboratory thermometer to
measure body temperature?
• Why does the mercury not fall or rise in a
clinical thermometer when taken out of
mouth?

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

13. TRANSFER OF HEAT
• Heat can transfer from place to place
• Heat can transfer through the
substances as well as in the absence
of substances, i.e., in vacuum.
• Let us see how heat can transfer in
solids.
• For this let us do a small activity.

14. Transfer of heat
• For this we need an alluminium
rod, 4 alpins, candle wax, candle,
match box, stand etc.
• See me how to setup the
apparatus for the activity.

15. ACTIVITY
• Take an alluminium rod of 15 to 20cm.
Length.
• Put 4 alpins at equidistance at one end
of the rod.
• Lit a candle and pour a drop of each of
molten wax on heads of alpins.
• The alpins now stick to aluminium rod.
• Fix this rod to a stand.

16. ACTIVITY
• Put the candle
under the free end
of aluminium rod
for 3-4 minutes.
• We can observe
that alpins start
falling from free
end to fixed end.

17. CONCLUSION
• In other words alpins
are start falling from
heating end/hot end
to non-heating/cold
end.
• This is because heat
get transferred from
hot end to cold
through the solid

18. CONDUCTION
• The phenomenon of transfer of heat
through hot end to cold end is called as
“CONDUCTION.”
• Can you give some examples for the
solids through which heat can be
conducted?
• All the metallic substances and graphite
can conduct the heat through them.

19. CONDUCTION
conduction

20. CONDUCTORS
• The substances in which heat can be
conducted are called as
‘CONDUCTORS’.
• Can all the solids conduct heat
through them?
• Let us study how heat can transfer
through liquids and gases in the next
class.

21. Convection
Activity
Procedure : Take a beaker or Round bottom flask. Fill it two-thirds
with water, heat it .Wait till the water in the flask is still. Place a
crystal of potassium permanganate at the bottom of the flask
gently using a straw. Now, heat the water by placing the candle
just below the crystal.

22. The transfer of heat from a hotter object to a
colder object without any medium in
between
Heat from the sun reaches the earth by
radiation
RADIATION

23. Transfer of heat

24. Sea Breeze
During the day, the land gets heated faster than the water. The air over
the land becomes hotter and rises up. The cooler air from the sea
rushes in towards the land to take its place. The warm air from the land
moves towards the sea to complete the cycle. The air from the sea is
called the sea breeze. To receive the cooler sea breeze, the windows
of the houses in coastal areas are made to face the sea.

25. land breeze
The water cools down more slowly than the land.
At night the sea is warm and the land is cool. The
air above the sea is warm. The air above the land
is cool. So, the cool air from the land moves
towards the sea. This is called the land breeze.

26. KINDS OF CLOTHESWE WEAR IN SUMMER AND
WINTER
• SUMMER-COTTON CLOTHES
• WINTER –WOOLEN CLOTHES