T1 BAB 7

Heat 1

The diagram shows an experiment to investigate transfer of heat using three conductors. Each rod is heated until the thumb tack drops. The time taken for the thumb tack to drop is recorded. Arrangement of apparatus

Copper rod

Glass rod

Time taken

15cm

60 seconds

15cm 120 seconds

Iron rod

15cm 90 seconds

Which of the following shows the correct heat conduction properties of the materials in the experiment? A B C D

Bad Glass rod Iron rod Copper rod Glass rod

Good Iron rod Copper rod Iron rod Copper rod

Very good Copper rod Glass rod Glass rod Iron rod PMR 2004

2

The diagram shows a hanging cardboard spiral.

When a lighted candle is placed under the cardboard spiral, it spins because A B C D

the candle displaces heat by radiation heat from the candle is conducted upwards the cardboard spiral becomes lighter when the air is hot the hot air under the cardboard spiral experiences convection PMR 2005

3

The diagram shows a heat transfer system in a building.

Which of the following activities uses the same principle as the above diagram? A B C D

Letting ice melt Boiling water in a kettle Ironing clothes with an iron Washing clothes using a washing machine PMR 2005

4

Houses in tropical countries are usually painted white to A B C D

absorb heat radiate heat detect heat reflect heat PMR 2007

5

Diagram 2 shows matter in state X changing to state Y when heat is released.

X

Y Diagram 2

Which of the following statements is true about the particles as the matter changes from state X to state Y? A B C D

The kinetic energy of the particles decrease The distance between the particles become far apart The particles take the shape of the container The size of the particles increases PMR 2007

6 7

Diagram 4 shows a fire alarm system. Diagram 5 shows the heating of three metal rods P, Q, and R. A thumb-tacks is attached at the end of each rod by a layer of plasticine.

Diagram 4 P, Q, R and S are steps by which the alarm works.

P – Bimetallic strip expands and bends Q – Bimetallic strip touches the contact screw and the circuit is complete Diagram 5 R – The fire increases the room temperature S – The fire alarm bell rings The time taken for the thumb-tacks to drop is recorded in Table 3. Choose the correct sequence of steps to make the alarm works A B C D

R P R P

P Time/s Q Q R

Thumb-tack atSP Thumb-tack at Q Q 150 210 R S P S Table 3 Q S

Thumb-tack at R 90

PMR 2007 Which of the following shows the metals in ascending order of their conductivity of heat? A B C D

Q, R, P R, Q, P P, Q, R Q, P, R PMR 2007

8

Diagram 5 shows two identical glasses, P and Q, which are stuck together.

Diagram 5 Glass Q is dipped into the hot water for a few minutes. What makes the glasses able to be separated easily? A B C D

Glass Q contracts more than glass P Glass Q expands more than glass P Glass Q and glass P expand at the same rate Glass Q and glass P contract at the different rate PMR 2008

1

(a) Diagram 6.1 shows a thermometer used in a laboratory. (PMR 2008)

Diagram 6.1 What happens to the mercury when the bulb is placed in hot water? ____________________________________________________________________ (1 mark) (b) Diagram 6.2 shows the condition of a bimetallic strip in a heating process.

Diagram 6.2 Why does the bimetallic strip bend when heated? ____________________________________________________________________ ____________________________________________________________________ (1 mark)

(c) Diagram 6.3 shows a fire alarm system.

Diagram 6.3 (i)

When there is a fire, the bimetallic strip bends. In the coloured region provided in Diagram 6.3, draw an arrow to show the direction of the bending of the strip.

(ii)

Explain how the fire alarm works when the bimetallic strip is heated. ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ (2 marks)

(d) Diagram 6.4 shows a method to remove a very tight metal cap of a bottle.

Diagram 6.4 Why do we use hot water to remove the tight metal cap easily? ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ (1 mark) (e) Diagram 6.5 shows some electrical cables.

Diagram 6.5

(i)

What happens to the electrical cables during cold weather?

____________________________________________________________ (1 mark) (ii) Give one reason for the answer in 6(e)(i). ____________________________________________________________ ____________________________________________________________ (1 mark)

Heat Paper 1 1. A 2. D 3. B 4. D 5. C 6. A 7. D 8. B Paper 2 1 (a) Mercury expands (b) Metal K and metal L expand by different amounts on heating (c) (i)

(ii) During a fire the brass expands more than the iron, and so the bimetallic strip bends inwards and completes the electric circuit to sound the fire alarm (d) The tight metal cap will expand (e) (i) During cold weather the electric cable will snap (ii) Electric cable will contract during cold weather