7.2 Heat Flow - Science Form 1
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Transcript of 7.2 Heat Flow - Science Form 1
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• When an object is heated, the particles move faster. !
• Particles moves further apart. !
• The object expands
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• When an object is cooled, the particles move slower (less energy) !
• The particles moves closer. !
• Contraction process occurs
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DemonstrationBall 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.
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Conclusion
Solid expand when heated and contract when cooled.
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DemonstrationMercury expanding and contracting
in thermometer
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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
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Conclusion
Liquid expand when heated and contract when cooled.
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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
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Conclusion
Gas expand when heated and contract when cooled.
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Question 1
What happen when an object is heated?
Answer
The object expands.
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Question 2
What happen when a liquid is cooled?
Answer
The liquid contracts.
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Question 3
What happen when gases is heated?
Answer
The gases expands.
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Heat Flow1. Heat flows in three different ways:
A. Conduction
B. Convection
C. Radiation
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Conduction1. 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.
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Conduction3. Heat transfer from hot area to cold
area.
4. The BIGGER the different in HEAT, the faster the HEAT flows
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Conduction1. 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.
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Conduction3. Heat transfer from hot area to cold
area.
4. The BIGGER the different in HEAT, the faster the HEAT flows
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Convection1. 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.
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Convection1. 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.
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Radiation1. 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.
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Question 1
How does heat flows?
Answer
Heat flows from hot area to cold area.
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Question 2
Name three ways of heat flows.
Answer
Conduction, convection and radiation
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Question 3
What effect heat flows?
Answer
The temperature different.
The BIGGER the different in HEAT, the faster the HEAT flows