This slide contains the history of heat. It will answer your questions about heat, the sources of heat and how can affect solid, liquid and gas molecules.

1. Nina Marie Alban
IV-Bacquerel
*

2. *Even in the ancient times, it
was understood that light and
heat are different. Fire was
considered to be one of the
elements, but the ancients
had noticed that while the fire
burned it give light and heat
but after it subsided the
embers continued to give
heat.

3. *Joseph Black – He
noticed that a kettle filled
with water and ice placed
over a fire did not change
in temperature till all the
ice was melted. He
suggested that heat flows
like a fluid.

4. *

5. *Heat is thermal
energy that is
absorbed, given up
or transferred from
one body to another.

6. *The temperature of
a body is a measure
of its ability to give
up heat to, or absorb
heat from another
body.
(modern physics p.167)

7. *
HEAT?

8. • The sun is the
primary source
of heat energy.
• Most of the
sun’s heat is
radiated back
into space and
only small
amount of it
reach the earth
to keep it
warm.

9. Rubbing or Friction – heat can be
produced when two objects are being
rubbed together.

10. Burning- is one of the common ways of
producing Heat. When something burns, it
produces flame and also heat.

11. Electricity

12. *

13. *
•Heat flows from warmer objects to cooler
objects. When a warmer object is in contact
with a cooler object, it will transfer heat to the
cooler object.
• This will go on until both objects have the
same temperature. At this point, they are in
the state of thermal equilibrium.
• For example, a bottle of soda is taken out from
refrigerator and placed on a table. The table
which is at room temperature, will transfer
heat to the bottle. Eventually, their
temperature will be equal and thermal
equilibrium will be achieved.

14. *
•Most matter expands when heated and
contracts when cooled.
• Two common examples of the effects of
heat are a boiled egg and a thick glass
cracking when hot water is poured onto
them.
• The increase in size of objects when they
are hot is called expansion. The decrease
in their size when they are cooled is called
contraction

15. *
•The atoms or molecules in a solid
vibrate at all temperatures.
•As the temperature increases,
they vibrate more vigorously and
this pushes the atoms further
apart. The volume of the solid
increases and the expansion is
said to occur.

16. *Expansion and Contraction
of Liquids
*When a liquid is heated, the molecules
of the liquid have more energy and
move more vigorously. The movement of
the molecules gradually overcomes the
forces of attraction between molecules,
allowing them to have greater freedom
to move over greater volumes. Thus, the
liquid expands.

17. *Expansion and Contraction of Gases
• The molecules of a gas are far part
compared with the molecules in a solid
and a liquid. The gas molecules move at
a high speeds in all direction.
• If a gas is confined in a container whose
volume is variable, the volume of the
gas will increase with increasing
temperature. The volume will decrease
as the temperature drops.

18. *