Chemistry – Year 9 – Track 2 – 2017 Page 1 of 12

DIRECTORATE FOR QUALITY AND STANDARDS IN EDUCATION

Department of Curriculum Management

Educational Assessment Unit

Annual Examinations 2017

YEAR 9 CHEMISTRY TIME: 2 hours

Name: ______________________________________

Class: ______________________________________

Useful Data Atomic numbers and relative atomic masses are shown in the periodic table printed on a separate page.

Marks Grid [ For Examiner’s use only ]

Question

No.

Section A Section B

1 2 3 4 5 6 7 8 9

Max

Mark 10 10 10 10 10 10 20 20 20

Theory

Total

Actual

Mark

Theory Paper: 85% Practical: 15% Final Score: 100%

Track 2

Page 2 of 12 Chemistry – Year 9 – Track 2 – 2017

SECTION A – Answer ALL questions. This section carries 60 marks.

1) The picture below shows a melting ice cube.

a) What kind of change (chemical / physical) is happening here?

____________________________________________________________________ [1]

b) What is the melting point of pure water?

____________________________________________________________________ [1]

c) What do we mean in chemistry, when we say that a substance is pure?

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d) What happens to the melting point of ice if it has salt mixed with it?

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e) Water can be produced by reacting hydrogen with oxygen.

i. Write a word equation for this reaction.

________________________________________________________________ [2]

ii. What kind of change is happening here?

________________________________________________________________ [1]

iii. In this reaction, identify one substance that is an element and another that is a

compound.

Element: _____________________________________________________

Compound: _____________________________________________________ [2]

f) Mention one difference between a chemical and a physical change.

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________________________________________________________________________

____________________________________________________________________ [1]

Chemistry – Year 9 – Track 2 – 2017 Page 3 of 12

2)

a) In an experiment to determine the percentage of oxygen in

air, a student decided to use iron wool to react with oxygen

in a known amount of air. The volume of air decreased

gradually until it did not change any more. The diagram

shows the setup used.

i. Iron reacted with oxygen in air in the presence of water vapour. What is this reaction

called?

________________________________________________________________ [1]

ii. The initial volume of air in the test tube was 150 cm3. Assuming oxygen is present in

its usual proportion in air, calculate the final volume of air remaining.

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________________________________________________________________ [2]

iii. Iron is used in the construction industry as it is a strong and relatively cheap material.

Mention the most practical solution to prevent iron from undergoing this reaction in

the construction industry.

________________________________________________________________ [1]

b) The reaction above happens at room temperature. However, at high temperatures, iron

reacts directly with oxygen.

i. What is the name of this kind of reaction?

________________________________________________________________ [1]

ii. Write a word equation to show what is happening in this reaction.

________________________________________________________________ [2]

iii. What type of oxide is produced?

________________________________________________________________ [1]

c) O2, is one of two allotropes that exist for oxygen.

i. Give the name of the other allotrope of oxygen.

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ii. What is the function of this allotrope in Earth’s atmosphere?

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Page 4 of 12 Chemistry – Year 9 – Track 2 – 2017

3) Water exists mainly as fresh or sea water. Only fresh

water is suitable for drinking. However, fresh water

is in short supply and humans always struggled to

find sources of drinking water.

In Malta, people used to excavate large underground

wells like the one shown in the picture. Rain water

used to collect in them during winter and they served

as storage for the hot summer months when water

was scarce.

a) Rain water tends to be slightly acidic.

i. Name a gas that occurs naturally in air which affects the acidity of rain water.

________________________________________________________________ [1]

ii. What is the pH of normal rain water? _________________________________ [1]

b) Although water collected in these underground wells is suitable for drinking, it contains

more impurities and we say that it is hard water.

i. What does the phrase “hard water” mean?

________________________________________________________________ [1]

ii. Which substance, present in Maltese rock, causes water to be hard?

________________________________________________________________ [1]

iii. Hardness is either temporary or permanent. What is the difference between these two

types of hardness in terms of ions present in solution?

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iv. Mention one way to remove temporary hardness from water.

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v. Mention one problem caused by hardness in water.

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c) As the population of Malta increased, reverse osmosis plants were introduced to cater for

the ever-increasing demand for fresh water. Describe briefly how this process works.

________________________________________________________________________

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____________________________________________________________________ [2]

http://www.pcurtis.com

Cross section of a well.

Chemistry – Year 9 – Track 2 – 2017 Page 5 of 12

4) When lithium reacts with chlorine, they form lithium chloride.

a) What kind of bond forms when lithium reacts with chlorine?

____________________________________________________________________ [1]

b) Using dot cross diagrams (showing all electron shells), show how lithium and chlorine

atoms combine to form lithium chloride.

[4]

When carbon reacts with oxygen, they form carbon dioxide.

c) What kind of bond forms between carbon and oxygen?

____________________________________________________________________ [1]

d) Using a dot cross diagram (showing outer electron shells only), show the bonding present

in carbon dioxide.

[2]

e) Bromine has two isotopes; bromine-79 and bromine-81. They exist in the ratio of 50.69 %

and 49.31 % respectively. Calculate the relative atomic mass of bromine.

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Page 6 of 12 Chemistry – Year 9 – Track 2 – 2017

5) Acids are a group of substances that have characteristic chemical properties.

a) Acids are dangerous chemicals, especially when they are concentrated. Which property

makes acids so dangerous?

________________________________________________________________________

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b) Name another property which is characteristic to acids.

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c) What makes a substance acidic?

________________________________________________________________________

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Bases are another group of substances that react with acids.

d) Name one base that is insoluble in water.

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e) What is the name given to bases that are soluble in water?

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f) Write a balanced chemical equation for the reaction between copper(II) oxide and

hydrochloric acid.

____________________________________________________________________ [2]

g) Why is the reaction in (f) considered to be a neutralisation reaction?

________________________________________________________________________

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h) Using a pH meter, how would you determine that the reaction in (f) came to an end?

Assume that copper(II) oxide is present in excess.

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Chemistry – Year 9 – Track 2 – 2017 Page 7 of 12

6) A student was heating a mixture of iron and sulfur to

produce iron(II) sulfide. The student was required to use

exact amounts of iron and sulfur so that the substances

reacted completely.

a) Write a balanced chemical equation, including state

symbols, for the reaction between iron and sulfur.

____________________________________________________________________ [3]

b) The student had 1 gram of iron filings and 10 grams of sulfur powder available. The student

decided to use all the iron. Calculate:

i. The amount of iron in moles.

____________________________________________________________________

________________________________________________________________ [1]

ii. The amount of sulfur in moles required to react completely with iron. (Show your

working.)

____________________________________________________________________

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________________________________________________________________ [2]

iii. The amount of sulfur in grams that the student needs to weigh for this reaction.

____________________________________________________________________

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c) Once the amounts of iron and sulfur were accurately weighed, what should the student do

to ensure that the iron and sulfur prepared in a) react completely.

________________________________________________________________________

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d) Calculate the amount of iron(II) sulfide, in grams, that would be produced in this

experiment.

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Page 8 of 12 Chemistry – Year 9 – Track 2 – 2017

SECTION B – Answer TWO questions only on the foolscaps provided.

This section carries 40 marks.

7) In 1852, Henri Giffard, a French engineer, built the first

airship. Airships are huge balloons that are filled with a light

gas so that they float in air. Airships used to be filled with

hydrogen gas. In 1937, the Hindenburg exploded when a

spark ignited the hydrogen it contained. 35 people on board

the airship died, as well as one person on the ground.

a) Why do you think airships were filled with hydrogen gas?

____________________________________________________________________ [1]

b) Which one of these gases: helium, nitrogen or oxygen; would you use to replace hydrogen

gas for this purpose? Give a reason for your choice.

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____________________________________________________________________ [2]

It is estimated that the Hindenburg contained 4000 kg of hydrogen gas. Hydrogen can be

obtained by the reaction of zinc with hydrochloric acid.

c) Write a balanced chemical equation, including state symbols, for the reaction between zinc

and hydrochloric acid to produce zinc chloride and hydrogen.

____________________________________________________________________ [3]

d) Calculate the amount of zinc, in kilograms, that would be required for this amount of

hydrogen to be produced.

________________________________________________________________________

____________________________________________________________________ [2]

e) What is the test for hydrogen gas?

____________________________________________________________________ [1]

f) The statements below describe a method to prepare hydrogen in the laboratory. Write

numbers to place the following steps in order. [6]

When the tap is opened, hydrogen is collected in the gas jar.

The gas jar is positioned at a higher position than the conical flask so that

hydrogen can be collected by upward delivery.

A delivery tube connects the conical flask to a gas jar that will be used to collect

the gas.

A conical flask is filled with a few grams of zinc.

The tap funnel is filled with hydrochloric acid.

A tap funnel is connected to the conical flask by means of a rubber bung.

http://www.wsj.com/ http://www.wsj.com/ http://www.wsj.com/

Chemistry – Year 9 – Track 2 – 2017 Page 9 of 12

g) Draw a labelled diagram to show the setup you would use to produce hydrogen gas. Use

the apparatus in the table below:

conical flask tap funnel rubber bung delivery tube gas jar

gas jar cover stand and clamp zinc HCl acid

[5]

8) Sodium carbonate is a substance that is used as a water softener. It is bought from hardware

stores and supermarkets in the form of crystals. These crystals contain water that is an

important part of their structure. A chemistry student was given a task to determine the amount

of water in sodium carbonate crystals.

a) What is the name given to water that is contained in these crystals?

____________________________________________________________________ [1]

b) The statements below describe what this student should do to determine the amount of

water in sodium carbonate crystals. However, they are not in order.

Write a number next to each step to put them in order. [6]

The crucible was reweighed with some sodium carbonate crystals.

Steps 4 and 5 were repeated until constant mass was achieved.

An empty crucible was weighed on a digital balance.

The crucible was allowed to cool and weighed.

The crucible with sodium carbonate crystals in it was placed on a tripod fitted

with a pipe clay triangle.

A Bunsen burner was used to heat the crucible.

Page 10 of 12 Chemistry – Year 9 – Track 2 – 2017

This student obtained the following results:

Initial mass of hydrated sodium carbonate 2.00 g

Final mass of anhydrous sodium carbonate 0.74 g

c) What is the relative formula mass of Na2CO3?

____________________________________________________________________ [1]

d) Calculate the amount of water in grams in the sodium carbonate crystals.

____________________________________________________________________ [1]

e) What is the relative molecular mass of water?

____________________________________________________________________ [1]

f) Convert the amount of water in (d) into amount in moles.

____________________________________________________________________ [1]

g) Convert the amount of anhydrous sodium carbonate into amount in moles.

____________________________________________________________________ [1]

h) Find the formula of hydrated sodium carbonate from the results obtained in (f) and (g).

________________________________________________________________________

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____________________________________________________________________ [2]

i) Write a balanced chemical equation, including state symbols, to show what happens when

hydrated sodium carbonate was heated in the crucible.

____________________________________________________________________ [3]

j) Find the percentage by mass of sodium in anhydrous sodium carbonate.

________________________________________________________________________

____________________________________________________________________ [2]

k) When hydrated sodium carbonate is exposed to air for a long time, the crystals become

partially anhydrous to form a white powder. What is the name of this process?

___________________________________________________________________ [1]

Chemistry – Year 9 – Track 2 – 2017 Page 11 of 12

9) The chemical name of table salt is sodium chloride. It is very

important since it has many uses such as to preserve food, as a

flavour enhancer and to remove ice / snow from roads.

Salt is found either dissolved in seas and oceans or deposited

between layers of rock. In either case, to obtain salt from seawater

or rock salt, different techniques are used.

In Malta, we obtain salt from sea water.

a) Describe how you would produce sodium chloride crystals from seawater in the laboratory.

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b) Draw a labelled diagram of the setup you would use. You must use the following

equipment: evaporating basin, tripod, beaker, wire gauze, Bunsen burner.

[5]

c) In Malta, salt is obtained on a large scale from salt pans. How is this process similar to the

one done in the laboratory?

________________________________________________________________________

________________________________________________________________________

____________________________________________________________________ [2]

http://www.trover.com/

Page 12 of 12 Chemistry – Year 9 – Track 2 – 2017

In the United Kingdom, salt is mainly obtained from rock salt. It is excavated (mined) from

between layers of rock, so the salt is mixed with bits of rock.

d) Describe how you would separate the particles of rock from the sodium chloride solution.

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e) Draw a labelled diagram of the setup you would use to separate the particles of rock from

the salt solution.

You must use the following equipment: beakers, filter funnel and filter paper.

[3]

f) If sodium chloride crystals stand in air, they would absorb water vapour and produce a

concentrated solution. What is this process called?

____________________________________________________________________ [1]