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SCIENCE DEPARTMENT
YEAR 10 IGCSE PHYSICS 0625
CONDUCTION CONVECTION AND RADIATION
NAME:_____________________________________TIME: 50 MINUTES.
1.
What are the three methods of heat transfer?
[3]
Conduction, Convection and Radiation
2.
What is the mechanism of heat transfer in a solid?[2]
Conduction. Particles vibrate and pass on energy to neighbouring particles
3.
Why are metals (such as iron and copper) better heat conductors than non-metals [1]
Metal have free mobile electrons and particles are closely packed.
4.
Why do metals feel cold when touched ?[2]
Metals are good conductors. Transfer heat away from the hand.
5.
In Fig. 9.1, a pin is attached to the end of each
aluminium, copper, iron, glass and brass rod by a
thin wax layer. Very hot water is placed in the
container.
a) Which pin will drop first? [1]
Copper
b) Which pin will drop last?[1]
Glass
c) What
can
you
conclude
from
the
observations above? [1]
Different metals have different conductivity. Some materials
are better in conducting heat than others.
6.
What are the uses of good heat conductors?[1]
Cooking utensils, electrical wiring to transmit electricity,
7.
Why is the car engine radiator made from copper? [1]
Copper is a good conductor to absorb and conduct heat from the hot
liquid
8.
What are the uses of poor heat conductors? [1]
Handles in cooking pans, clothing,
9.
Houses in cold countries use double glazing windows that traps air
between two pieces of glass panes, as shown in Fig. 9.2. 9.2. What is
the purpose of having this kind of window?[2]
Air is a poor conductor of heat. It
prevents heat loss by conduction by convection.
10.
(a) Between a solid, liquid and gas, which one is best heat conductor?[1]
Solids
(b) Which one is the worst?[1]
11.
Gas
Ice was placed at the bottom of a test-tube filled with
water. The top part of the tube is heated until the water
there boils, as shown in Fig. 9.3.
a) What happens to the ice? [1]
Ice does not melt
b) What does this experiment show?[1]
Water is a poor conductor of heat.
(c) In the experiment, why was the ice wrapped with a wire gauze?
To make ice heavy and sink to the bottom to
avoid floating of ice.
12.
What is the method by which heat is transferred in a fluid (liquid or
gas)?[1]
Convection
Change in density
of molecules. Cold molecules are
dense and sink. Hot molecules are
less dense and rises.
13.
What causes heat convection?[2]
14.
Potassium permanganate crystals (purple) were placed in at the bottom of a beaker filled with
water. The water is then warmed slowly by a Bunsen flame, as shown in Fig. 9.4. What is the
direction of the convection current that will be observed?[1]
Stream of purple rises and falls in circular paths
15.
(a) Fig.9.5 shows a place near the sea during the day. What is the direction of wind? [1]
Sea to land
16.
In an electric kettle, why is the heating coil placed at the
Cold water at the
bottom is heated, expands
and rises.
bottom ? [1]
17.
Why does the air conditioner unit in a room placed at the top?[1]
Hot air is less dense and stays at the top.
18.
What is the method by which a hot object like the Sun transfer heat?[1]
Radiation
19.
How does the heat from the Sun reach Earth?[1]
Radiation
20.
A piece of bread is toasted in a toaster as shown in Fig. 9.7.
How is the heat transferred to the bread? [1]
Radiation
21.
(a) What kind of surface is the best heat emitter?[1]
Matt black( Dull and black)
(b) What kind of surface is the poorest heat emitter?[1]
Shiny (polished) white
22. Two thermometers were placed at equal distances from a container containing boiling water, as
shown in Fig. 9.8. The left side of the container is white and shiny while the right side is black and
dull. Which thermometer will show a bigger increase in
temperature? Why? [2]
Black and dull surface; it is a
good emitter of heat.
23.
What type of surface is the best heat absorber?[1]
Black and dull surface
24. Two stoppers were attached to different copper plates,as
shown in Fig. 9.9. Which stopper will drop first? Why? [2]
Stopped on the dull black surface.
Absorbs more heat
25.
Fig. 9.14 shows the basic structure of a solar water heater
placed on top of a roof. The copper tube is coated black.
Why?[2]
To absorb more heat from the sun.Black and dull
surfaces are good
absorbers
26.
. What is the reason for using a system of winding tube above ?[2]
Increases the surfaces area so that more heat is
absorbed.
27.
How a vacuum flask does minimises heat loss from the liquid it stores? [1]
 Plastic stopper prevents by conduction,
convection and evaporation.
 Vacuum reduces heat loss by conduction and
convection.
 The shiny silvered surface reduces heat by
radiation.
a) Fig. 9.11 shows the structure of a vacuum flask.How does the stopper prevents heat
Plastic stopper prevents by conduction,
convection and evaporation.
loss?[1]
b) How does the vacuum prevents heat loss?[1]
There are no particles in the
vacuum. Prevents heat loss by
conduction and convection.
c) How does the silvered wall prevents heat loss?[1]
Reflects the heat back to the liquid
d) In real use, hot water stored in a vacuum flask, did experience a slight heat loss.
How this is possible?[1]
The vacuum contains some air that causes convection.