Science questions, chapter 9

Nama / NameKelas / ClassTarikh / Date

Heat

44 marks. Use Practice to check each answer as you go, or Exam to answer everything against the clock first.

Section A: objective questions

12 marks

Choose the best answer for each question.

Question 1

What is the S.I. unit of heat?

Kelvin
Degree Celsius
Joule
Watt

Show answerHide answer

Heat is a form of energy, measured in joule (J). Kelvin and degree Celsius are units of temperature.

For the teacher: Remembering, low difficulty, standard 9.1.1

Textbook p. 206

Question 2

Heat always flows from

a colder object to a hotter object
a hotter object to a colder object
a smaller object to a bigger object
a bigger object to a smaller object

Show answerHide answer

Heat flows from a hotter region to a colder region, whatever the sizes of the objects.

For the teacher: Remembering, low difficulty, standard 9.2.1

Textbook p. 207

Question 3

200 mL and 100 mL of water are boiled in two identical beakers. Which statement is correct?

Both boil at the same temperature, but the 200 mL takes longer to boil
The 200 mL boils at a higher temperature than the 100 mL
The 100 mL boils at a higher temperature than the 200 mL
Both take the same time to boil because they have the same temperature

Show answerHide answer

Temperature depends on the movement of the particles, so both boil at 100 °C. The larger mass needs more heat, so it takes longer.

For the teacher: Understanding, low difficulty, standard 9.1.1

Textbook p. 206

Question 4

Which method of heat transfer allows the heat from the Sun to reach the Earth?

Conduction
Convection
Conduction and convection
Radiation

Show answerHide answer

Space is a vacuum. Only radiation can transfer heat without a medium.

For the teacher: Understanding, low difficulty, standard 9.2.2

Textbook p. 209

Question 5

Oven gloves are made of thick cloth. Why?

Cloth is a good heat conductor
Cloth is a heat insulator that prevents heat from flowing to the hand
Cloth absorbs heat well
Cloth radiates heat quickly

Show answerHide answer

Heat insulators prevent heat flow, so the hand is not scalded.

For the teacher: Applying, low difficulty, standard 9.2.3

Textbook p. 211

Question 6

During the day the Sun heats the land faster than the sea. Which statement explains the sea breeze that results?

Warm air from the land moves out to sea along the ground
Cool air from the land moves to the sea
Warm air above the sea rises and air from the land replaces it
Warm air above the land rises and cooler, denser air from the sea moves in to replace it

Show answerHide answer

The air above the land is warmer, less dense and rises. Cooler, denser air from the sea moves in, which is the sea breeze.

For the teacher: Understanding, medium difficulty, standard 9.2.2

Textbook p. 210

Question 7

Two objects are in thermal equilibrium. Which statement is correct?

They have the same temperature and there is no net transfer of heat between them
They have the same amount of heat
Heat still flows from one to the other at a constant rate
They are both at room temperature

Show answerHide answer

At thermal equilibrium the temperatures are equal, so there is no net heat flow. The amounts of heat may differ.

For the teacher: Remembering, low difficulty, standard 9.2.3

Textbook p. 212

Question 8

What happens to the particles of a solid when it is heated?

They become bigger
They move closer to one another
They vibrate faster and move further apart
They stop vibrating

Show answerHide answer

Heated particles vibrate faster and the distance between them increases, so the solid expands. The particles themselves do not change size.

For the teacher: Understanding, low difficulty, standard 9.3.1

Textbook p. 214

Question 9

Small gaps are left between the rails of a railway track. What is the purpose of the gaps?

To make the train ride faster
To prevent the rails from rusting
To allow the rails to expand in hot weather
To allow the rails to contract in hot weather

Show answerHide answer

Without the gaps the rails would buckle when they expand in hot weather.

For the teacher: Applying, low difficulty, standard 9.3.2

Textbook p. 214

Question 10

Diagram 1 shows the rise in temperature of the air in a white milk can J and a black milk can K after both were placed the same distance from a Bunsen burner for 10 minutes. What can be concluded?

Bar chart: can J (white) rose 12 degrees Celsius; can K (black) rose 31 degrees Celsius — Diagram 1

A black surface absorbs heat better than a white surface
A white surface absorbs heat better than a black surface
A black surface is a poor heat radiator
Colour has no effect on heat absorption

Show answerHide answer

The black can warmed by 31 °C but the white can only by 12 °C under the same conditions, so black absorbs heat better.

For the teacher: Analysing, medium difficulty, standard 9.4.1

Textbook p. 217

Question 11

The cooling unit of a refrigerator is placed at the top of the compartment. Why?

Cold air is less dense and rises to cool the food
Heat from the food is conducted upwards
Heat is radiated from the food to the walls
Cold air is denser and sinks, so a convection current cools all the food

Show answerHide answer

Air next to the unit cools, becomes denser and sinks. Warmer air rises to take its place, so a convection current cools the whole compartment.

For the teacher: Applying, medium difficulty, standard 9.2.1

Textbook p. 208

Question 12

A bimetallic strip of brass and iron is heated and bends so that the iron is on the inside of the curve. What does this show?

Iron expands faster than brass
Brass expands faster than iron
Brass contracts when heated
Both metals expand by the same amount

Show answerHide answer

The metal that expands more is on the outside of the curve. Brass is on the outside, so it expands faster than iron.

For the teacher: Analysing, medium difficulty, standard 9.3.2

Textbook p. 215

Section B: structured questions

32 marks

Answer all questions. Write your answers in the spaces provided.

Question 13

Choose whether each statement describes heat or temperature.

[1 mark] (a)It is measured in joule.

AHeatBTemperature

Show answerHide answer

Heat

[1 mark] (b)It is measured in degrees Celsius or kelvin.

AHeatBTemperature

Show answerHide answer

Temperature

For the teacher: Remembering, low difficulty, standard 9.1.1

Textbook p. 206

Question 14

Diagram 2 shows three thumbtacks K, L and M fixed with wax to a copper rod. One end of the rod is heated.

Copper rod heated at the left end with three thumbtacks K, L and M fixed by wax — Diagram 2

[1 mark] (a)State the method of heat transfer along the rod.

Show answerHide answer

Conduction1

Tick each point you got.

[1 mark] (b)Which thumbtack falls first?

Show answerHide answer

K is the nearest to the heat source, so the wax around it melts first.

Tick each point you got.

[2 marks] (c)Explain how heat travels along the rod.

Show answerHide answer

The particles that receive heat vibrate faster1
They collide with neighbouring particles and pass the heat along the rod1

Tick each point you got.

For the teacher: Understanding, low difficulty, standard 9.2.1

Textbook p. 207

Question 15

Diagram 3 shows the movement of air near a coast at night.

Air rising over the sea and sinking over the land; cool air moves from the land to the sea along the ground — Diagram 3

[1 mark] (a)Name the type of breeze shown.

Show answerHide answer

Land breeze1

Tick each point you got.

[2 marks] (b)Explain why the air above the sea rises at night.

Show answerHide answer

The sea cools more slowly than the land, so the air above the sea is warmer1
The warm air expands, becomes less dense and rises1

Tick each point you got.

[1 mark] (c)State the direction in which the breeze blows.

Show answerHide answer

From the land to the sea1

Tick each point you got.

For the teacher: Applying, low difficulty, standard 9.2.2

Textbook p. 210

Question 16

Diagram 4 shows the temperature of two objects P and Q in thermal contact, against time.

Line graph: P falls from 80 to 45 degrees Celsius, Q rises from 20 to 45 degrees Celsius, level from 12 minutes — Diagram 4

[1 mark] (a)Which object loses heat?

Show answerHide answer

Its temperature falls from 80 °C.

Tick each point you got.

[1 mark] (b)State the temperature at which the two objects are in thermal equilibrium.

Show answerHide answer

45 °C1

Tick each point you got.

[1 mark] (c)After how many minutes is thermal equilibrium reached?

Show answerHide answer

12 minutes1

Tick each point you got.

For the teacher: Analysing, low difficulty, standard 9.2.3

Textbook p. 212

Question 17

Four identical flat-bottom flasks, each containing 200 mL of boiling water at 95 °C, were left for 10 minutes: K uncovered, L covered with cotton, M covered with felt, N covered with aluminium foil. Diagram 5 shows the final temperatures.

Bar chart of final temperatures: K 58, L 83, M 80, N 66 degrees Celsius — Diagram 5

[1 mark] (a)State the manipulated variable.

Show answerHide answer

Type of material used to cover the flask1

Tick each point you got.

[1 mark] (b)Calculate the drop in temperature of flask L.

Show answerHide answer

95 − 83 = 12 °C1

Tick each point you got.

[2 marks] (c)Which material is the best heat insulator? Give a reason.

Show answerHide answer

Cotton1
Flask L had the smallest drop in temperature (12 °C) / its final temperature was the highest1

Tick each point you got.

[1 mark] (d)What is the purpose of flask K?

Show answerHide answer

Control / to compare with the flasks that are covered1

Tick each point you got.

[1 mark] (e)Explain why flask N cooled more than flask L.

Show answerHide answer

Aluminium is a heat conductor, so heat flows out quickly (cotton is an insulator)1

Tick each point you got.

For the teacher: Analysing, medium difficulty, standard 9.2.3

Textbook p. 212

Question 18

The lid of a glass bottle is very tight. Danish submerges the lid in hot water and is then able to open it.

[2 marks] (a)Explain why the lid becomes easy to open.

Show answerHide answer

The lid is heated, its particles vibrate faster and move further apart1
The lid expands, so it becomes loose1

Tick each point you got.

[1 mark] (b)A dented table tennis ball is placed in hot water and the dent disappears. Name the principle involved.

Show answerHide answer

Expansion of matter (the air inside the ball expands when heated)1

Tick each point you got.

For the teacher: Applying, medium difficulty, standard 9.3.2

Textbook p. 215

Question 19

A can of insecticide carries the warning: "Keep away from heat or fire!"

[2 marks] (a)Explain what might happen if the empty can is thrown into a rubbish dump that is heated by the Sun or burning.

Show answerHide answer

The gas left in the can is heated and expands1
The pressure inside increases and the can may explode1

Tick each point you got.

[1 mark] (b)Suggest one safe way to store the insecticide can.

Show answerHide answer

Any 1 points

Keep it in a cool place away from sunlight and fire1
Do not leave it in a hot car1

Tick each point you got.

For the teacher: Evaluating, medium difficulty, standard 9.3.2

Textbook p. 220

Question 20

Dayah finds it hard to sleep on a cold rainy night even when she uses one thick blanket. She wants a blanket that keeps her warmer.

[2 marks] (a)Suggest a design of a blanket that keeps her warmer.

Show answerHide answer

Several layers with air trapped between them (or fluffy fibres)1
Made of a heat insulator such as wool or fleece / with a shiny layer to reflect heat back1

Tick each point you got.

[2 marks] (b)Explain how your design reduces heat loss.

Show answerHide answer

Trapped air is a poor conductor (heat insulator)1
It reduces the heat lost from the body by conduction and convection1

Tick each point you got.

For the teacher: Creating, high difficulty, standard 9.2.3

Textbook p. 221

Question 21

Fuel tank lorries are usually painted white or silver.

[2 marks] (a)Explain why.

Show answerHide answer

White / silver surfaces are poor absorbers of heat1
Less heat enters the tank, so less fuel evaporates1

Tick each point you got.

[1 mark] (b)Name one daily-life item that is made dark and dull so that it absorbs heat well.

Show answerHide answer

Any 1 points

Cooking pot base1
Solar heater panel1
Black car body (any one)1

Tick each point you got.

For the teacher: Understanding, low difficulty, standard 9.4.1

Textbook p. 216

Back to notes Chapter 10 questions Model papers