The Ever-Changing Earth | WJEC GCSE Chemistry Exam Questions 2018

1a4 marks

The Earth’s crust contains more than 80 elements, including many metals. Some of the metals, such as gold, are found ‘native’ or uncombined, but most are bonded with other elements to form compounds.

The crust can be thicker than 80 kilometres in some spots and less than one kilometre thick in others.

Just six elements make up almost all of the Earth’s crust. These are aluminium, calcium, iron, oxygen, silicon and sodium.

Silicon is the second most abundant element. The amount of aluminium is approximately double the amount of calcium.

The chart shows the percentages of elements contained in the crust.

q4a-wjec-gcse-chemistry-june-2022-1f

i)

Use the information given to label the remaining sections of the chart.

[2]

ii)

Underline the approximate fraction of elements in the crust which are metals.

[1]

\frac{1}{2}

\frac{1}{3}

\frac{1}{4}

\frac{3}{4}

iii)

Tick (√) the statement which best explains why most metals are not found native in the crust.

[1]

most metals have higher melting points than gold $□$

most metals are magnetic $□$

most metals are more reactive than gold $□$

most metals are radioactive $□$

How did you do?

1b4 marks

Tectonic plates are huge sections of the crust that move very slowly above the mantle. The places where plates meet are called plate boundaries.

The diagram shows one type of plate boundary.

q4b-wjec-gcse-chemistry-june-2022-1f

i)

Describe how new rock is formed at this plate boundary.

[3]

ii)

Underline the name of this type of plate boundary.

[1]

conservative destructive constructive

How did you do?

Did this page help you?

1a1 mark

This question is about the uses of gases present in air.

Air is a mixture of different gases. Each gas has different uses. The gases are present in different amounts as shown below.

Gas	Amount present in air	Boiling point (°C)
N₂	78.04 %	−195.8
O₂	20.95 %	−183.0
CO₂	0.03 %	−78.5
Ar	0.93 %	−189.2
Ne	18 ppm	−246.0
He	5 ppm	−268.9
Kr	1 ppm	−152.3
Xe	0.08 ppm	−107.1
H₂	0.5 ppm	−257.9
CH₄	2 ppm	−164.0
N₂O	0.5 ppm	−88.5

ppm = parts per million

Separating a complex mixture!

Air is firstly compressed and cooled which turns it into a liquid. Carbon dioxide freezes and is removed as solid dry ice. The rest of the mixture goes on to a fractionating column where it is slowly warmed allowing most of the substances to be separated.

q6a-wjec-gcse-chemistry-june-2019-1h

Tick (✓) the main reason why hydrogen is not separated during the fractional distillation of liquid air.

hydrogen is a highly reactive gas	$□$
only 0.5 ppm of hydrogen is present	$□$
hydrogen does not become liquid on cooling to −200°C	$□$
hydrogen has a higher boiling point than helium	$□$

How did you do?

1b1 mark

Tick (✓) the reason why carbon dioxide becomes a solid during the first part of the process.

carbon dioxide has a boiling point above −200°C	$□$
carbon dioxide has a melting point above −200°C	$□$
carbon dioxide has a melting point below −200°C	$□$
carbon dioxide has a boiling point below −200°C	$□$

How did you do?

1c3 marks

Describe, in terms of boiling points, how nitrogen, argon and oxygen are separated during fractional distillation.

How did you do?

1d

2 marks

The noble gases are present in very small quantities in the air. The amount of each gas produced per year is shown in the table.

Noble gas	World production (tonnes per year)
helium	28 000
neon	1 000
argon	700 000
krypton	8
xenon	0.6

Use the data to calculate the number of tonnes of air needed to produce 700000 tonnes of argon. Give your answer in standard form.

[2]

Mass of air needed = …….................................. tonnes

How did you do?

Did this page help you?

Volume of air before heating	50.0 cm³
Volume of air after heating and cooling	40.5 cm³

Gas	Chemical formula	Percentage found in the atmosphere (%)
argon	Ar	0.93
carbon dioxide	CO₂	0.0360
helium	He	0.0005
hydrogen	H₂	0.00005
methane	CH₄	0.00017
neon	Ne	0.0018
nitrogen	N₂	78.08
nitrous oxide	N₂O	0.00003
oxygen	O₂	20.95
ozone	O₃	0.000004


........................................	........................................

Most carbon dioxide is produced by electricity generation	$□$
Between 1900 and 2010 there was a massive increase in industry	$□$
The mean global temperature remained constant between 1950 and 1980	$□$
The average number of cars per home has increased steadily since the 1980s	$□$
The use of energy efficient appliances has increased since 2000	$□$

The Ever-Changing Earth (WJEC GCSE Chemistry)

Exam Questions