The Ever-Changing Earth (WJEC GCSE Chemistry)

Burning fossil fuels leads to global warming.

Explain how global warming arises and describe the problems caused.

Alfred Wegener proposed the theory of continental drift.

State the evidence that Wegener used to support his theory and explain why other scientists refused to accept it.

In the 1960s scientists studied the ocean floor at a constructive plate boundary. Their observations are summarised in the following diagram.

i) Describe what is happening at this boundary.

[2]

ii) Label the diagram clearly to show the oldest rock.

[1]

Global warming is believed to be mainly the result of increasing levels of carbon dioxide in the atmosphere.

i) State how the balance of carbon dioxide and oxygen is maintained in the atmosphere. Explain why levels of carbon dioxide are increasing and how this leads to global warming.

[3]

ii) Carbon capture and storage (CCS) is one possible method of reducing global warming.

Describe briefly how CCS is carried out.

[2]

Higher Tier Only

Oxides of nitrogen are released in vehicle exhaust fumes. They can cause smog in busy city centres as well as acid rain.

i) One oxide of nitrogen contains 30.4 g of nitrogen and 69.6 g of oxygen.

Find the simplest formula of this oxide. You must show your working.

[3]

A_r(N) = 14                           A_r(O) = 16

Simplest formula ………...............................................

ii) The oxide with this simplest formula is found to have a relative molecular mass of 92. Find its molecular formula.

[2]

Molecular formula ………...............................................

Fuels obtained from crude oil contain impurities. 

Explain how an impurity found in fuels can cause an environmental problem.

The following information is taken from some articles about global warming.

Greenhouse gases such as carbon dioxide keep heat close to the Earth’s surface making it a suitable temperature for life. Global warming is an increase of the Earth’s mean surface temperature due to the overproduction of greenhouse gases by burning fossil fuels such as gas, petrol and oil. Deforestation also contributes to this. With the growth of industry in the 1900s, humans began burning more fossil fuels to run our cars, trucks and factories. There is more carbon dioxide in the atmosphere today than at any point in the last 800,000 years.

The following charts show the mean global temperature every decade since the 1880s, the amount of carbon dioxide in the atmosphere from 1750-2010 and the main sources of carbon dioxide production today.

Figure 1

Figure 2

Figure 3

Draw a trend line on Figure 1.

Suggest why there was a large rise in the amount of carbon dioxide in the atmosphere after around 1950.

Give one way in which we are trying to reduce carbon dioxide emissions.

Some people say that changes in carbon dioxide levels are not responsible for global warming. Tick (√) the statement that supports this opinion.

The following diagram shows some of the Earth’s tectonic plates and the direction in which they move.

The boundary between the Nazca and South American plates is a destructive plate boundary. Describe what happens at a destructive boundary.

Draw a cross (×) on the diagram to show a constructive plate boundary.

Describe what happens at this boundary

State one effect of plates sliding past each other.

In 1912 Alfred Wegener suggested that all the continents must once have been joined together as one big mass.

Diagrams A-D show the position of the Earth’s continents at different times during the last 225 million years.

Put the letters of the diagrams in the correct order on the timeline below. 

225 million years ago ........................

150 million years ago ........................

100 million years ago ........................

today ........................

Describe two pieces of evidence that Wegener used to support his theory of continental drift.

1. ......................................................................................................................................

2. ......................................................................................................................................

Wegener’s idea was finally accepted in 1960 and led to the modern theory of plate tectonics.

Which of the following events is likely to occur at a boundary where two plates slide past each other? 

The graphs below show the changes in carbon dioxide levels and atmospheric temperature between 1960 and 2005.

Describe how the evidence from the graphs can be used to support and to oppose the statement:

“Global warming is caused by releasing carbon dioxide into the atmosphere.”

Support .............................................................................................................................

Oppose .............................................................................................................................

Natural gas is mainly methane, CH₄. Complete the equation for its combustion in air by drawing diagrams to represent all the molecules formed.

The percentage of oxygen in air can be found by using the apparatus shown below.

50cm³ of air was trapped in one of the syringes. The air was passed forwards and backwards over the heated copper. The copper reacted with the oxygen in the air producing solid copper(II) oxide. The final volume of gas was recorded when the apparatus had cooled to room temperature.

Results

i) Use the results to calculate the percentage of oxygen in air.

[2]

Percentage of oxygen in air = ........................... %

ii) Suggest why the value for the percentage of oxygen in air calculated in part (i) is lower than the expected value.

[1]

iii) State what happens to the amount of carbon dioxide inside the apparatus during the experiment. Give the reason for your answer.

[2]

Copper(II) oxide can be formed by heating copper(II) nitrate.

Balance the equation for the reaction.

.....Cu(NO₃)₂   →   .....CuO   +   .....NO₂   +   O₂

A small minority of scientists believe that it is changes in solar activity (i.e. changes in the brightness and warmth of the sun) that causes global warming. The graphs below show the changes in solar activity and atmospheric temperature since 1880.

Using the information from the graphs, state how well the evidence supports the argument that solar activity is the cause of global warming.

Most scientists believe the main cause of global warming is the increase in carbon dioxide levels in the atmosphere.

i) State the main cause of this increase in carbon dioxide levels.

[1]

ii) Describe one method of reducing current atmospheric carbon dioxide levels.

[1]

Fossil fuels such as coal release sulfur dioxide into the atmosphere when burned. This causes acid rain. Describe how acid rain is formed and its effects on the environment.

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.

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.

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

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

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

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.

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

The diagram shows the movement of the major tectonic plates.

Explain what happens at destructive and constructive plate boundaries.

Diagrams may be included in your answer

This Earth and its atmosphere today are not like the early Earth and its atmosphere.

Describe and explain how the surface of the early Earth and its atmosphere have changed to form the surface of the Earth and its atmosphere today.

There were many ideas about how the Earth was formed from a molten ball of rock and minerals. 

At one time scientists thought the features of the Earth were caused when the molten ball of rock and minerals cooled and wrinkled.

Scientists now have evidence that the Earth has a layered structure.

Describe the layered structure of the Earth. You should indicate the relative sizes of the layers.

At one time scientists thought the Earth’s continents were formed in fixed positions when the molten ball of rock and minerals cooled and wrinkled. 

In 1912, the scientist Alfred Wegener suggested his idea about how Earth’s continents formed.

Describe Wegener’s idea of how Earth’s continents formed.

For 200 million years the proportions of the different gases in the atmosphere have been much the same as today. Over the past 150 years the amount of carbon dioxide in the atmosphere has increased from 0.03% to 0.04%.

Describe how carbon dioxide is released into the atmosphere:

i) by human and industrial activity.

[2]

ii) from carbonate rocks by geological activity.

[2]

Explain how the seas and oceans can decrease the amount of carbon dioxide in the atmosphere. 

i) Give two reasons why the amount of carbon dioxide in the atmosphere is increasing gradually.

[1]

ii) Give two effects that increasing levels of carbon dioxide in the atmosphere may have on the environment.

[1]