1. Heat and temperature

2. Questions to think about…
Why do things become hot or cold?
What are the effects of heat gain and heat loss on matter?
What is the difference between heat and temperature?
What are the effects of expansion and contraction in our daily lives?
What is temperature?
What are good and poor conductors of heat?
What is heat?

3. What is heat? Heat is a form of energy that makes things warm.
Things that give out heat are known as sources of heat.
Burning fuels such as wood and gas produces heat.
Electrical appliances like electric irons, water heaters and electric ovens are also sources of heat.

4. What is heat? The Sun is our main source of heat.
It keeps the Earth and living things on Earth warm.

5. What is temperature? Temperature is how hot or cold something is.
Temperature is measured in degree Celsius (°C).
Thermometers:
These are used to measure temperature.
Thermometers usually have a liquid inside the bulb. The level of the liquid rises or falls according to temperature changes.
A thermometer
bulb

6. What is temperature?
There are different types of thermometers for different purposes.
placed under armpit or tongue
A digital thermometer like the one on the right can measure the temperature of our surroundings.
A laboratory thermometer is used to measure temperature in Science experiments.
A clinical thermometer such as the one above is used to measure temperatures a few degrees below or above the body temperature of 37°C.

7. What is temperature? Heat sensor and datalogger
A heat sensor can be connected to a datalogger. These can be used to measure temperature.
datalogger
heat sensor

8. Reading a thermometer
Reading temperature on a thermometer – how to read correctly:
Step 1: Hold the thermometer upright.
Step 2: Look at the level of the liquid.
Step 3: Position your eyes at the same level as the liquid in the thermometer (see the next slide).
Step 4: Read the marking nearest to the level of the liquid in the thermometer.

9. Reading a thermometer
Reading temperature on a thermometer – how to read correctly:

10. What is the difference between heat and temperature?
Beaker B
Beaker A
60°C
30°C
To heat up the same amount of water to a higher temperature, more heat is needed. Thus, the water in beaker A has more heat than the water in beaker B.
Beakers A and B have the same amount of water. But the water in beaker A has a higher temperature than the water in beaker B.

11. What is the difference between heat and temperature?
Beaker D
Beaker C
80°C
80°C
However, there is more heat in beaker C than in beaker D since more heat is needed to warm up a greater amount of water.
Beaker C has more water than beaker D. The water in beakers C and D is at 80°C.

12. Why do things become hot or cold?
Things become hotter when they gain heat.
Things become colder when they lose heat.
Heat travels from a hotter place to a colder place until both places reach the same temperature.

13. Why do things become hot or cold?
The mug is gaining heat from the hot chocolate. This will cause the temperature of the mug to rise.
The noodles is losing heat to the surroundings, which will cause the temperature of the noodles to fall.

14. What are the effects of heat gain and heat loss on matter?

15. Change in state of water
Water gains heat and changes from a liquid to a gas (water vapour) when heated.
Water vapour loses heat and changes back to a liquid when cooled.
Water droplets

16. Expansion and contraction of a solid
A solid expands when it gains heat.
A solid contracts when it loses heat.

17. Expansion and contraction of a liquid
A liquid expands when it gains heat.
A liquid contracts when it loses heat.
A flask of coloured water is placed in hot water
A flask of coloured water is placed in cold water

18. Expansion and contraction of a gas
A gas expands when it gains heat.
A gas contracts when it loses heat.
In hot water
A balloon is placed over the mouth of a conical flask.
In cold water

19. What are the effects of expansion and contraction in our daily lives?
Why are the wires hung loosely?
Why are gaps left in the pavement?

20. What are good and poor conductors of heat?
Metals allow heat to flow through them easily.
They are called good conductors of heat.
Materials like wood, plastics, rubber and air do not allow heat to flow through them easily.
They are called poor conductors of heat.

22. The end