7.2 Heat Flow - Science Form 1

7.2) Heat Flow
Chapter 7 : Heat
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• When an object
is heated, the
particles move
faster.
!
• Particles moves
further apart.
!
• The object
expands

• When an object is
cooled, the
particles move
slower (less
energy)
!
• The particles
moves closer.
!
• Contraction
process occurs

Demonstration
Ball and Ring Experiment (Solid)

Demonstration
Ball and Ring Experiment
• Initially, the metal ball can go through the ring.
!
• When the metal ball is put into hot water, it will
expands. It will stuck and can not go through
the ring.
!
• When the ball is put into the cold water, the
particles move closer to each other. The ball is
able go through the ring again.

Conclusion
Solid expand when heated and
contract when cooled.

Demonstration
Mercury expanding and contracting
in thermometer

Demonstration
• When the thermometer, is put into hot
water, the temperature will rise. (Mercury
inside thermometer is expanding)
!
• When the thermometer is put into cold
water, the temperature will decrease.
(Mercury inside thermometer is
contracting)
Mercury expanding and contracting
in thermometer

Conclusion
Liquid expand when heated and

Demonstration
Gas expansion and contraction

Demonstration
• When the test tube is heated, the bubbles
is produced. (The gas particles inside the
test tube is expanding and push out
through the delivery tube)
Gas expansion and contraction

Conclusion
Gas expand when heated and

Question 1
What happen when an object is heated?
Answer
The object expands.

Question 2
What happen when a liquid is cooled?
Answer
The liquid contracts.

Question 3
What happen when gases is heated?
Answer
The gases expands.

Heat Flow
1. Heat ﬂows in three different ways:
A. Conduction
B. Convection
C. Radiation

Conduction
1. Conduction : ﬂow of heat through
solid.
2. Example : You can feel the spoon
become hot when stir a hot bowl of
soup.
3. Heat ﬂows from higher temperature to
lower temperature.

Conduction
3. Heat transfer from hot area to cold
area.
4. The BIGGER the different in HEAT,
the faster the HEAT ﬂows

Demonstration
Heat conduction in solids

Convection
1. Convection : ﬂow of heat through
liquid and gas.
2. The hot ﬂuid expands and become
less dense (form convection current
-a cycle).
3. Heat transfer from hot area to cold
area.

Demonstration
Heat convection in liquids

Demonstration
Heat convection in gases

Radiation
1. Radiation : ﬂows of heat through
empty space or vacuum.
2. The heat transfer in the form of
wave.
3. Example : Transfer of heat from the
Sun to the Earth.

Demonstration
Radiation of Heat

Question 1
How does heat ﬂows?
Answer
Heat ﬂows from hot area to cold area.

Question 2
Name three ways of heat ﬂows.
Answer
Conduction, convection and radiation

Question 3
What effect heat ﬂows?
Answer
The temperature different.
The BIGGER the different in HEAT, the faster the HEAT
ﬂows

7.2 Heat Flow - Science Form 1

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