1. Book 1 Section 4.1 Conduction
Roasted chestnuts
Conduction in solids, liquids and gases
Conduction and particle motion
Check-point 1
Examples of conduction and insulation
Factors affecting the rate of conduction
Check-point 2 1 2 3 4
Book 1 Section 4.1 Conduction

2. Book 1 Section 4.1 Conduction
Roasted chestnuts
In preparing roasted chestnuts, raw chestnuts are fried together with black sand in a large iron wok.
Book 1 Section 4.1 Conduction

3. Book 1 Section 4.1 Conduction
Roasted chestnuts
Why is an iron wok suitable?
Iron wok is a good conductor of heat
Why is black sand added?
To improve conduction of heat to chestnuts
Book 1 Section 4.1 Conduction

4. 1 Conduction in solids, liquids and gases
When we cook food using a pan,
heat is transferred to the pan and to the food through direct contact.
 conduction
Expt 4a
Conduction in solids, liquids and gases
Book 1 Section 4.1 Conduction

5. Book 1 Section 4.1 Conduction
Experiment 4a
Conduction in solids, liquids and gases
How does heat transfer along a solid rod?
Set up the apparatus.
Use the same amount of wax to stick drawing pins along the copper rod.
Heat one end of the rod.
copper rod
insulating board
drawing pins
What happens to the drawing pins?
Book 1 Section 4.1 Conduction

6. Book 1 Section 4.1 Conduction
Experiment 4a
Conduction in solids, liquids and gases
What kind of solid conducts heat faster?
Put a copper rod, an iron rod, a glass rod and a wooden rod into a beaker of hot water.
Feel the ends of the rods.
Which rod gets hot first?
very hot water
glass
wood
iron
copper
Book 1 Section 4.1 Conduction

7. Book 1 Section 4.1 Conduction
Experiment 4a
Conduction in solids, liquids and gases
What kind of solid conducts heat faster?
Set up the apparatus. (The rods are of same thickness and length).
Heat the ends of the metal rods.
aluminium
copper
iron
drawing pins
Which drawing pin falls first?
Book 1 Section 4.1 Conduction

8. Book 1 Section 4.1 Conduction
Experiment 4a
Conduction in solids, liquids and gases
Does water conduct heat fast?
Use wire gauze to keep some ice under water at the bottom of a boiling tube.
Gently heat the top part of the water.
Does the ice melt?
water
wire gauze
ice
boiling tube
Book 1 Section 4.1 Conduction

9. Book 1 Section 4.1 Conduction
Experiment 4a
Conduction in solids, liquids and gases
Does air conduct heat fast?
thermometer
cardboard tube
heater
Set up the apparatus.
Take the reading of the thermometers after a while.
Is air a good conductor?
Book 1 Section 4.1 Conduction

10. Book 1 Section 4.1 Conduction
Experiment 4a
Conduction in solids, liquids and gases
Video
Video
Video
Video
Video
4.1 Expt 4a - Conduction in solids, liquids and gases
Book 1 Section 4.1 Conduction

11. 1 Conduction in solids, liquids and gases
Expt 4a shows that solids, liquids and gases conduct heat at different rates.
Metals are good conductors of heat.
Non-metals are poor conductors, or good insulators.
Book 1 Section 4.1 Conduction

12. 1 Conduction in solids, liquids and gases
The Expt 4a also shows that…
…heat is transferred from a region of higher temp to a region of lower temp.
Conduction is the transfer of heat from the hot part to the cold part of an object. Energy (but not matter) is transferred in the process.
Book 1 Section 4.1 Conduction

13. 1 Conduction in solids, liquids and gases
Does the orientation of the rod matter?
Example 1
Book 1 Section 4.1 Conduction

14. Book 1 Section 4.1 Conduction
Example 1
Does the orientation of the rod matter?
Phoebe heats two identical metal rods. Which rod will heat up first? Why?
They heat up at the same rate.
Energy transferred from the hot end to the cold end by conduction is NOT affected by the orientation of the rod.
Book 1 Section 4.1 Conduction

15. 2 Conduction and particle motion
All matter is made up of atoms, each of which has a nucleus with electrons moving around.
Book 1 Section 4.1 Conduction

16. 2 Conduction and particle motion
When one part of a solid is heated, the atoms there vibrate faster and gain KE.
The slower neighbouring atoms are hit.
 vibrate more rapidly
 Temp of the neighbouring parts 
atoms are closely packed, can only vibrate to and fro
Simulation
4.1 Conduction and particle motion
Book 1 Section 4.1 Conduction

17. 2 Conduction and particle motion
This process takes place in all solids, but….
The rate of energy transfer across an object by this process is slow.
In metals, the loosely held outermost electrons can move freely among the atoms.
 free electrons
Book 1 Section 4.1 Conduction

18. 2 Conduction and particle motion
When one part of a metal is heated,
the free electrons there move faster and collide with the neighbouring atoms.
 temp of the colder parts 
This process is rapid
 very high rate of conduction of metals.
Book 1 Section 4.1 Conduction

19. 2 Conduction and particle motion
In liquids and gases, the atoms are not strongly held together.
Faster atoms cannot hit
cannot pass on energy to neighbouring atoms effectively.
Liquids and gases are poor conductors of heat.
4.2 Microscopic description of conduction in matters
Simulation
Book 1 Section 4.1 Conduction

20. Book 1 Section 4.1 Conduction
2 Conduction and particle motion
Houses in desert
Example 2
Book 1 Section 4.1 Conduction

21. Book 1 Section 4.1 Conduction
Example 2
Houses in desert
In a desert, it is hot in the daytime and cold at night.
The walls of houses there are often made of mud. It is important that the walls are thick.
Book 1 Section 4.1 Conduction

22. Book 1 Section 4.1 Conduction
Example 2
Houses in desert
(a) What is the direction of the flow of heat through the wall in the daytime?
From outside to inside.
(b) What is the direction of the flow of heat through the wall at night?
From inside to outside.
Book 1 Section 4.1 Conduction

23. Book 1 Section 4.1 Conduction
Example 2
Houses in desert
(c) Explain how the thick mud walls help maintain the temp of the house.
Mud is a poor conductor.
A thick mud wall keeps the house…
warm at night by slowing the flow of heat from inside to outside.
cool in the daytime by slowing the flow of heat from outside to inside.
Book 1 Section 4.1 Conduction

24. Book 1 Section 4.1 Conduction
Check-point 1 – Q1
In conduction, in which of the following directions is energy transferred?
A From high-temp area to low-temp area.
B From low-temp area to high-temp area.
C From area of high internal energy to that of low internal energy.
D The direction is different in metals and non-metals.
Book 1 Section 4.1 Conduction

25. Book 1 Section 4.1 Conduction
Check-point 1 – Q2
Most metals are good conductors because
A their atoms are closely packed.
B their atoms vibrate faster when heated.
C there are free electrons moving among the atoms.
Book 1 Section 4.1 Conduction

26. Book 1 Section 4.1 Conduction
Check-point 1 – Q3
Mary heats three rods of the same size.
Rods A : iron
Rod B : copper
Rod C : glass
Which rod will heat up first?
Book 1 Section 4.1 Conduction

27. 3 Examples of conduction and insulation
a Keeping warm
Humans and animals keep warm by insulation.
Air is a poor conductor of heat
 Humans wear clothes that trap air
 energy will be conducted away slowly
Book 1 Section 4.1 Conduction

28. Book 1 Section 4.1 Conduction
3 Examples of conduction and insulation
b Feeling hot or cold when touching an object
At the same temp, a metal surface feels colder than a wooden surface because…
…metal conducts energy away from your hand more easily.
 makes you feel colder
Book 1 Section 4.1 Conduction

29. 3 Examples of conduction and insulation
c Cooking
Cooking utensils are mainly made of metals
effective heat transfer from stove to food
Handles made of poor conductors (e.g. plastic, wood)
insulating
allow us to grasp with bare hand
Book 1 Section 4.1 Conduction

30. Book 1 Section 4.1 Conduction
4 Factors affecting the rate of conduction
Factors enhancing the rate of conduction (from one end to the other):
Larger temp difference
Smaller distance between two ends
Better conducting material
Larger cross-sectional area
Video
4.2 The Chinese clay pot
Book 1 Section 4.1 Conduction

31. Book 1 Section 4.1 Conduction
Check-point 2 – Q1
Which of the following gives the main reason why woollen gloves keep us warm in cold winters?
A Wool absorbs heat.
B Wool is soft.
C Wool traps air.
D Wool is a good conductor.
Book 1 Section 4.1 Conduction

32. Book 1 Section 4.1 Conduction
Check-point 2 – Q2
Which of the following explains why a tile floor feels colder than a wooden floor?
A Tile is a better conductor than wood.
B Wood is a better conductor than tile.
Book 1 Section 4.1 Conduction

33. Book 1 Section 4.1 Conduction
Check-point 2 – Q3
Frying-pans are made of metal because it is a good ____________ of heat.
Handles of frying-pans are made of wood because it is a good ____________ of heat.
conductor
insulator
Book 1 Section 4.1 Conduction

34. Book 1 Section 4.1 Conduction
The End
Book 1 Section 4.1 Conduction