GCSEScienceWJECScience (Double Award)ChemistryExam QuestionsChemical Substances, Reactions & Essential ResourcesThe Ever-Changing Earth

The Ever-Changing Earth (WJEC GCSE Science (Double Award): Chemistry): Exam Questions

Exam code: 3430

1 hour15 questions

2 marks

The diagram shows the structure of the Earth.

Figure: Cross-section diagram of the Earth showing four layers pointed to by lines from outside to centre — two unlabelled blank lines (outermost two layers), then "outer core" already filled in as the given example (third layer), then one more unlabelled blank line for the innermost/central layer

Use words from the box to label the layers of the Earth's structure on the diagram.

mantle

inner core

crust

One has been done for you.

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3 marks

Alfred Wegener's theory of continental drift describes how the Earth's continents have moved to their current positions.

Underline the correct words in the brackets to complete the sentences which describe the evidence on which Wegener based his theory.

Wegener found that there are similar ( trees / animals / rocks ) on different continents and that some continents have ( mountains / coastlines / oceans ) which fit together. Most people did not believe Wegener's theory at the time because he could not explain how the continents ( moved / formed / melted ).

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1 mark

Circle the name given to the large pieces which make up the Earth's crust.

plates

fractions

segments

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4 marks

Human activity causes emissions of about 6 billion tonnes of carbon dioxide into the atmosphere each year. Carbon capture effectively traps the emissions from power plants or factory chimneys before they enter the atmosphere and contribute to global warming. There are different ideas regarding what to do with the gas once it has been captured.

Proposal 1

Photograph of two large, ribbed, blue plastic storage bags on the deep ocean floor, with one bag in the foreground and another behind it, illustrating proposed underwater storage of captured carbon dioxide.

One idea is to pipe the trapped gas to the ocean floor more than 4 km below sea level where the temperature is around 2 °C and the pressure can be up to 750 times atmospheric pressure. The captured carbon dioxide would be stored in a solid-liquid state in huge plastic bags. Each of these bags would hold about two days' worth of global emissions. Some scientists have predicted that we might find a way in the near future to use this 'solid' carbon dioxide as a fuel, possibly by combining it with hydrogen to produce methanoic acid for use in fuel cells.

Proposal 2

Photograph of grey-gloved hands holding a mound of coarse, beige-brown granular material, representing the refined carbon-emissions product used to make sodium hydrogencarbonate, or baking soda.

Another idea is to refine the carbon emissions to make a high-grade product which will then be used to make sodium hydrogencarbonate, also known as baking soda. Baking soda is in high demand in the pharmaceutical sector to help treat conditions from heartburn to kidney disease. It is found in ear and eye drops. It can also be used to produce components of detergents, sherbet powder and glass. Some manufacturers are even using it to remove acidic gases from factory emissions.

(i) Tick (✓) the two correct statements which explain why carbon dioxide would be in a solid-liquid state when in plastic bags at the deep ocean floor.

the pressure is higher than at sea level and the temperature is lower	$□$
the pressure and temperature are both lower than at sea level	$□$
particles are closer together at a higher pressure	$□$
carbon dioxide is not a gas at any temperature or pressure	$□$
particles are closer together at a higher temperature	$□$

[2]

(ii) Suggest two reasons why proposal 2 might be viewed as a better solution than proposal 1.

[2]

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1 mark

A great deal of scientific research into global warming has happened over the last 30 years.

More recently, two new contrasting theories linked to global warming have been widely reported. These are outlined below.

Solar activity

A small number of scientists believe that changes in solar activity (changes in the brightness and warmth of the Sun) is causing global warming. Solar activity occurs on the surface of the Sun when nuclear reactions cause flares to be released, high winds to occur and a release of high energy particles from the Sun.

Global dimming

Some scientists believe that global warming is increasing the Earth's mean temperature, but that global dimming is preventing it from increasing even more. Global dimming is the reduction in the amount of radiation reaching the Earth's surface from the Sun. It is thought to be caused by an increase of aerosol particles in the Earth's atmosphere caused by pollution, dust and smog, as well as volcanic eruptions. These particles absorb solar energy and reflect sunlight back into space.

Figure 1 shows the mean atmospheric temperature, carbon dioxide concentration in the atmosphere and solar activity between 1930 and 2010.

Figure 1

Year	Mean atmospheric temperature (°C)	CO₂ concentration (ppm)	Solar activity (arbitrary units)
1930	13.6	309	3.9
1940	13.6	311	4.0
1950	13.8	316	4.2
1960	13.9	320	4.2
1970	14.0	331	4.0
1980	14.2	342	3.9
1990	14.3	358	3.7
2000	14.4	370	3.7
2010	14.6	383	3.6

Figure 2 shows the mean atmospheric temperature within a 20-mile radius of the Mount Pinatubo volcano in the Philippines between 1990 and 2000. Mount Pinatubo erupted in 1991.

Figure 2

Year	Mean atmospheric temperature (°C)
1990	15.1
1991	14.7
1992	14.8
1993	14.7
1994	14.7
1995	14.6
1996	14.7
1997	14.8
1998	14.7
1999	14.8
2000	14.9

Tick (✓) the box that best describes the change in carbon dioxide concentration in the atmosphere between 1930 and 2010.

Carbon dioxide concentration increased by approximately 10 ppm every 10 years	$□$
Carbon dioxide concentration increased more between 1970 and 2010 than it did between 1930 and 1960	$□$
Carbon dioxide concentration increased more between 1930 and 1960 than it did between 1970 and 2010	$□$
There is no trend to the change in carbon dioxide concentration between 1930 and 2010	$□$

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2 marks

A newspaper report states that global warming is caused by increases in atmospheric carbon dioxide levels and by increases in solar activity.

Explain whether the data in Figure 1 supports this claim.

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1 mark

Figure 2 shows that the mean atmospheric temperature near Mount Pinatubo decreased after the volcanic eruption of 1991. Suggest why scientists would not use these findings to explain how volcanic activity affects global temperatures.

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1 mark

State one industrial method that is being developed to reduce the concentration of carbon dioxide in the atmosphere.

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3 marks

The Earth's original atmosphere contained about 95% carbon dioxide. Today, the atmosphere contains 0.04% carbon dioxide. Explain why the level of carbon dioxide decreased over geological time.

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1 mark

When carbon dioxide turns limewater milky, calcium hydroxide is produced.

Give the formula of calcium hydroxide.

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

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5 marks

The diagram shows how the Earth's continents are arranged today.

Figure: World map showing the modern arrangement of the continents, with South America, Africa and Australia shaded in a darker tone

In 1912, Alfred Wegener proposed the theory of continental drift.

(i) Use statements from the table to answer parts I. and II. below.

A	there are similar animals on different continents
B	there are similar fossils on different continents
C	only Europe, Asia and Africa were once joined
D	all of the continents were once joined
E	there is a jigsaw fit of different continents
F	there are similar rocks on different continents
G	none of the continents were joined

I. Give the letter of the statement that describes how Wegener suggested the continents were originally arranged.

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

[1]

II. Give the letters of three pieces of evidence that Wegener used to support his theory.

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

[3]

(ii) Underline the correct word in the brackets to complete the following sentence.

Wegener could not explain how the continents moved but it is now known that this happens because of ( conduction / convection / radiation ) currents in the Earth's mantle.

[1]

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4 marks

The table shows how the mean temperature of the Earth's atmosphere has increased between 1960 and 2010.

Year	Mean temperature (°C)
1960	13.9
1970	14.0
1980	14.2
1990	14.3
2000	14.4
2010	14.6

(i) Underline the mean temperature of the Earth's atmosphere in 2020 if this trend continued.

15.0

14.4

14.8

[1]

(ii) Name the gas which is mainly responsible for the temperature increase.

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

[1]

(iii) Give two effects of global warming.

Effect 1 ..................................................................................................................................................................

Effect 2 ..................................................................................................................................................................

[2]

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Stage	Major events	Gases present in the atmosphere
1	volcanic eruptions	carbon dioxide, water vapour, methane, ammonia
2	oceans form	carbon dioxide, methane, ammonia
3	green plants evolve	carbon dioxide, nitrogen, oxygen
4	most carbon dioxide becomes locked in rock and fossil fuels	nitrogen, oxygen, water vapour

Year	Carbon dioxide emissions (million tonnes)
Year	USA (million tonnes)	India (million tonnes)
1955	700	100
1965	800	250
1975	1150	250
1985	1150	450
1995	1150	600
2005	1400	900
2015	1300	1850

Water vapour evaporated to form clouds	$□$
The Earth cooled so water vapour condensed	$□$
Bacteria and algae turned the water vapour into liquid water	$□$
There were no more volcanoes to produce water vapour	$□$

all of the fuels contribute to acid rain and global warming when they burn	$□$
fuels A and C contribute to acid rain and global warming when they burn	$□$
only fuel C contributes to acid rain and global warming when it burns	$□$
none of the fuels contribute to acid rain and global warming when they burn	$□$

fuel C will run out after fuels A and B	$□$
fuel C is easier to store than fuel A	$□$
fuel A burns more easily than fuel C	$□$
fuel B is the cleanest fuel	$□$
fuel B is easier to store than fuel C	$□$
fuel B will never run out	$□$
fuel A is less harmful to the environment than fuel C	$□$
fuel A is less cost efficient than fuel B	$□$

Type of plate	Density (g/ cm³)
continental	4.7
oceanic	5.0