Science questions, unit 7

Nama / NameKelas / ClassTarikh / Date

Rusting

44 marks. Use Practice to check each answer as you go, or Exam to answer everything first. Ask a grown-up to help you mark the written answers.

Section A: objective questions

10 marks

Choose the best answer for each question.

Question 1

What is the colour of rust?

Light grey
Reddish-brown
Bright yellow
Dark green

Show answerHide answer

Mr Zaki says the rusty window handle is reddish-brown.

For the teacher: Remembering, low difficulty, standard 7.1.1

Textbook p. 164

Question 2

Diagram 1 shows a rusty hinge. Which statement describes the hinge?

A rusty door hinge with rusted screws — Diagram 1

Its surface is smooth and shiny.
Its screws are strong and hard to break.
It is white in colour.
Its surface is rough and its screws are brittle.

Show answerHide answer

A rusty object is reddish-brown, rough and brittle.

For the teacher: Understanding, low difficulty, standard 7.1.1

Textbook p. 164

Question 3

Ravi and Chan sit in a park. Diagram 2 shows two benches. Which bench is rusty and why?

A wooden bench and a rusty iron bench in a park — Diagram 2

The wooden bench, because wood rusts.
Both benches, because all benches rust.
The iron bench, because iron rusts.
Neither bench, because they are outside.

Show answerHide answer

Objects made of iron rust. Wood does not rust.

For the teacher: Applying, low difficulty, standard 7.1.2

Textbook p. 166

Question 4

Which factors cause iron to rust?

Water and air
Oil and air
Sunlight and soil
Heat and plastic

Show answerHide answer

The investigation with iron wool shows that the presence of water and air causes rusting.

For the teacher: Remembering, low difficulty, standard 7.1.3

Textbook p. 168

Question 5

Anhydrous calcium chloride is put in a test tube in the rusting investigation. Why?

To add air to the tube
To make the iron wool heavier
To absorb moisture so that the tube is dry
To stop air from entering the tube

Show answerHide answer

Anhydrous calcium chloride absorbs moisture, so there is air but no water in the tube.

For the teacher: Understanding, medium difficulty, standard 7.1.3

Textbook p. 169

Question 6

Cooking oil is poured on top of boiled tap water in a test tube. What is the oil for?

To make the water boil
To prevent air from entering the water
To remove moisture from the iron wool
To make the iron wool rust faster

Show answerHide answer

Boiled water has no air. The oil stops air from going back into the water.

For the teacher: Understanding, medium difficulty, standard 7.1.3

Textbook p. 169

Question 7

Which of these is a way to prevent an iron gate from rusting?

Leaving it in the rain
Washing it with salt water
Wrapping it with wet cloth
Painting it

Show answerHide answer

Paint covers the iron so that water and air cannot touch it.

For the teacher: Remembering, low difficulty, standard 7.1.4

Textbook p. 170

Question 8

Diagram 3 shows food cans made of iron. The surface of the iron is covered with tin. Which way of preventing rusting is used?

Plating with a rustproof metal
Applying grease
Coating with plastic
Painting

Show answerHide answer

Rustproof metals such as tin and aluminium are plated onto the surface of iron objects.

For the teacher: Applying, medium difficulty, standard 7.1.4

Textbook p. 170

Question 9

In a shop, Mother chooses a sardine can that is not dented. Why?

A dented can is more expensive.
A dented can is lighter.
The dented part may have rusted and the food may be unsafe.
A dented can cannot be opened.

Show answerHide answer

The dented part of the can may have rusted. Food exposed to rust is unsafe to eat.

For the teacher: Applying, medium difficulty, standard 7.1.5

Textbook p. 171

Question 10

Four identical iron nails are kept for one week. Which nail will rust the most?

A nail in a dry bottle with anhydrous calcium chloride
A nail in a bowl of tap water
A nail in boiled water with a layer of oil on top
A nail in a jar of oil

Show answerHide answer

Only the nail in tap water has both water and air. The other three have no water or no air.

For the teacher: Analysing, high difficulty, standard 7.1.3

Textbook p. 168

Section B: structured questions

34 marks

Answer all questions. Circle the answer or write it in the space.

Question 11

Diagram 4 shows a rusty window handle and a rusty hinge.

[1 mark] (a)What is the colour of the rust?

AReddish-brownBBlueCWhite

Show answerHide answer

Reddish-brown

[1 mark] (b)The surface of a rusty hinge is

AroughBsmooth

Show answerHide answer

rough

[1 mark] (c)The screws of a rusty hinge are

AstrongBbrittle

Show answerHide answer

brittle

Brittle means it breaks easily.

For the teacher: Remembering, low difficulty, standard 7.1.1

Textbook p. 164

Question 12

Chan's mailbox is rusty. Ravi's mailbox is made of plastic.

Two pupils with a rusty mailbox and a plastic mailbox — Diagram 5

[1 mark] (a)Which material do you think Chan's mailbox is made of?

AIronBPlasticCWood

Show answerHide answer

Iron

[1 mark] (b)Why does Ravi's mailbox not rust?

Show answerHide answer

It is made of plastic / plastic does not rust / it is not made of iron1

Tick each point you got.

[1 mark] (c)Name one other object that can rust.

Show answerHide answer

Any iron object, e.g. nail, hinge, axe, bench, fence, needle1

Tick each point you got.

For the teacher: Understanding, low difficulty, standard 7.1.2

Textbook p. 166

Question 13

Diagram 6 shows the investigation to find the factors that cause rusting. Tube A has iron wool only, tube B has anhydrous calcium chloride, tube C has boiled tap water and oil, and tube D has tap water. Each tube has 20 g of iron wool and a stopper. They are left for four days.

Four test tubes with iron wool only, calcium chloride, boiled tap water under oil, and tap water — Diagram 6

[1 mark] (a)Which tube contains rusty iron wool?

AABBCCDD

Show answerHide answer

[1 mark] (b)Give a reason for your answer in (a).

Show answerHide answer

It has both water and air1

Tick each point you got.

[1 mark] (c)Why does the iron wool in tube B not rust?

Show answerHide answer

There is no water / it is dry (the calcium chloride absorbs moisture)1

Tick each point you got.

[1 mark] (d)Why does the iron wool in tube C not rust?

Show answerHide answer

There is no air (boiled water has no air and the oil stops air entering)1

Tick each point you got.

[1 mark] (e)What is the conclusion of this investigation?

Show answerHide answer

Water and air (both) cause rusting / iron rusts when water and air are present1

Tick each point you got.

For the teacher: Applying, low difficulty, standard 7.1.3

Textbook p. 169

Question 14

A pupil investigates whether water and air cause rusting. Each test tube has 20 g of iron wool. Name each variable.

[1 mark] (a)The manipulated variable

Show answerHide answer

The presence of water and air1

Tick each point you got.

[1 mark] (b)The responding variable

Show answerHide answer

The condition of the iron wool (rusty or not rusty)1

Tick each point you got.

[1 mark] (c)The constant variable

Show answerHide answer

The quantity (mass) of the iron wool, 20 g1

Tick each point you got.

For the teacher: Understanding, low difficulty, standard 7.1.3

Textbook p. 168

Question 15

Diagram 7 shows four ways to prevent iron objects from rusting. Match each picture with the way used.

[1 mark] (a)P

AApplying oil or greaseBCoating with plasticCPlating with a rustproof metalDPainting

Show answerHide answer

Applying oil or grease

[1 mark] (b)Q

AApplying oil or greaseBCoating with plasticCPlating with a rustproof metalDPainting

Show answerHide answer

Coating with plastic

[1 mark] (c)R

AApplying oil or greaseBCoating with plasticCPlating with a rustproof metalDPainting

Show answerHide answer

Plating with a rustproof metal

[1 mark] (d)S

AApplying oil or greaseBCoating with plasticCPlating with a rustproof metalDPainting

Show answerHide answer

Painting

For the teacher: Applying, low difficulty, standard 7.1.4

Textbook p. 170

Question 16

Your class does a rust prevention project in the school compound. Diagram 8 shows a rusty iron fence that needs to be restored.

A rusty iron fence and two people talking about repainting it — Diagram 8

[1 mark] (a)Suggest a suitable way to prevent the fence from rusting again.

Show answerHide answer

Paint it1

Tick each point you got.

[1 mark] (b)Suggest a suitable way to prevent the chain of a bicycle in the bicycle shed from rusting.

Show answerHide answer

Apply oil or grease1

Tick each point you got.

[1 mark] (c)Why is oil or grease better than paint for a bicycle chain?

Show answerHide answer

The chain moves, so paint would peel off / oil stays on moving parts and keeps water and air away1

Tick each point you got.

[1 mark] (d)State one benefit of painting the fence.

Show answerHide answer

It looks better / it lasts longer / it is safe to use1

Tick each point you got.

For the teacher: Creating, high difficulty, standard 7.1.4

Textbook p. 173

Question 17

Diagram 9 shows four test tubes with a needle. Tube D has anhydrous calcium chloride, which keeps the tube dry. They are left for a week.

Four test tubes with a needle: A tap water, B oil, C boiled tap water and oil, D anhydrous calcium chloride — Diagram 9

[1 mark] (a)Which needle becomes rusty?

AABBCCDD

Show answerHide answer

Adapted from textbook Mind Test 4 (p. 176). In the book, tube D holds a needle on its own and the textbook answer counts it as rusty because ordinary air carries water vapour. Here tube D is kept dry on purpose, so only tube A has both water and air.

[1 mark] (b)Why does the needle in A rust?

Show answerHide answer

It has water and air1

Tick each point you got.

[1 mark] (c)Why does the needle in C not rust?

Show answerHide answer

Boiled water has no air and the oil stops air entering, so there is no air1

Tick each point you got.

[1 mark] (d)Why does the needle in D not rust?

Show answerHide answer

There is no water (the anhydrous calcium chloride keeps it dry)1

Tick each point you got.

[1 mark] (e)What can you conclude from this investigation?

Show answerHide answer

Both water and air are needed for iron to rust1

Tick each point you got.

For the teacher: Analysing, medium difficulty, standard 7.1.3

Textbook p. 176

Question 18

A pupil says the handrail of a staircase is brittle and not safe to use. The staircase has rust on it.

Two pupils on a rusty staircase — Diagram 10

[1 mark] (a)Why is it unsafe to use the rusty handrail?

Show answerHide answer

It is brittle / it may break easily and the person may fall1

Tick each point you got.

[2 marks] (b)State two reasons why it is important to prevent rusting.

Show answerHide answer

Any two: safe to use / durable and not easily damaged / saves on maintenance cost / looks pleasant [1 mark each]2

Tick each point you got.

For the teacher: Evaluating, medium difficulty, standard 7.1.5

Textbook p. 172

Question 19

The spoons we use at home are exposed to water and air, but they do not rust.

[1 mark] (a)Suggest a reason why the spoons do not rust.

Show answerHide answer

Any 1 points

They are plated with a rustproof metal such as stainless steel (textbook answer)1
Accept: they are made of a material that does not rust / they are coated with a rustproof material1

Tick each point you got.

For the teacher: Evaluating, high difficulty, standard 7.1.5

Textbook p. 172

Question 20

Siti makes a rust removal solution. She mixes 100 mL of vinegar, salt and soda bicarbonate.

[1 mark] (a)She sprays the solution on a rusty object. How long does she leave it?

A5 minutesB5 hoursC5 days

Show answerHide answer

5 minutes

[1 mark] (b)Which tool does she use to clean off the rust?

AWire brushBCotton rollCTest tube

Show answerHide answer

Wire brush

[1 mark] (c)What should she do after preparing the solution?

AWash her hands with soap and waterBTaste the solutionCPour it into the sink without rinsing

Show answerHide answer

Wash her hands with soap and water

For the teacher: Remembering, low difficulty, standard 7.1.4

Textbook p. 174

Back to notes Unit 8 questions Model papers