Formation of Earth's Atmosphere (AQA GCSE Chemistry: Combined Science)

This question is about carbon dioxide in the atmosphere.

Up until 100 years ago and for the previous 200 million years, the amount of CO₂ in the atmosphere had remained unchanged.

Describe the natural processes by which plants and marine life remove carbon dioxide from the atmosphere.

The levels of carbon dioxide in the atmosphere have increased continually over the last one hundred years. 

Suggest two reasons for this increase.

The proportion of carbon dioxide has decreased since the early atmosphere.

One reason for this is plants undergoing photosynthesis. 

What other reasons are there for the decrease in carbon dioxide levels?

This question is about the Earth and its atmosphere.

The theories about how Earth’s atmosphere has developed have evolved and changed over time. 

Suggest two reasons for this.

The Earth and its atmosphere today are very unlike that of the early Earth as can be seen in Figure 1.

Figure 1

Describe and explain how the atmosphere of the early Earth has changed to the atmosphere that we know today.

Around 60 million years ago a large meteorite struck the Earth. 

The impact heated limestone in the Earth’s crust, releasing huge quantities of carbon dioxide.

Explain how CO₂ is released from limestone. 

You should include a balanced equation.

The graph in Figure 2 shows the percentage of carbon dioxide in the Earth’s atmosphere over the last 50 years.

Figure 2

Explain in as much detail as possible why we should be concerned about the information displayed in Figure 2.

Aside from water vapour, two main gases account for approximately 99% of the atmosphere.

Give the names of these gases.

Scientists now believe that over three billion years ago, Earth’s atmosphere consisted of a mixture of water vapour, carbon dioxide, methane and ammonia. 

The mixture has changed significantly since then.

Suggest two reasons for the decrease in water vapour and two for the decrease in carbon dioxide.

Describe how the gases in Earth’s early atmosphere (in the first billion years) formed.

Describe the composition of the Earth's early atmosphere and name the planets it was most similar to.

This question is about the amount of nitrogen and oxygen in the atmosphere. 

Scientists study the atmosphere on planets and moons in the Solar System to get a better understanding of how the Earth’s atmosphere has changed.

It is suspected that the early Earth’s atmosphere resembled that of Mars today. 

The table shows data about the atmosphere of Mars and Earth today.

The percentages of N₂ and O₂ in the Earth’s atmosphere of millions of years ago have changed.

Describe how the amounts of these gases have been changed and suggest what caused this change.

What type of organism was first responsible for producing oxygen on Earth and when did this occur?

Complete and balance the equation for photosynthesis, placing above the reaction arrow the condition needed for photosynthesis to occur.

__ CO₂    +   ____   ⟶    __C₆H₁₂O₆ + __O₂

Explain how deposits of limestone, coal and crude oil are formed.

It is thought that algae used gases in the atmosphere to form amino acids. 

The diagram shows the amino acid, alanine.

Which gases in the early atmosphere were the most likely sources of these elements?

Green plants undergo photosynthesis. 

Which numbers correctly balance the symbol equation for photosynthesis? 

 __ CO₂  +  __ H₂O       →    __ C₆H₁₂O₆   +   __ O₂

This question is about the atmosphere of Mars. 

The composition of its atmosphere is shown in the pie chart in Figure 1. 

Figure 1

Calculate the percentage of other gases on Mars. 

Earth contains a high amount of oxygen compared to Mars.

Describe two other differences between the atmosphere of Earth and Mars. 

It is thought when the Earth formed 4.5 billion years ago, the atmosphere was similar to that of Mars.

The growth of green plants and evolution of other organisms has changed the composition of the atmosphere over this period of time. 

Explain how. 

Carbon dioxide is a greenhouse gas that contributes to global warming. 

Suggest four effects of global climate change. 

This question is about carbon dioxide.

Carbon dioxide gas levels have remained the same over the last 200 million years. 

Complete the dot and cross diagram to show the bonding carbon dioxide gas in Figure 1. 

Figure 1

Explain why carbon dioxide is a gas at room temperature.

Describe the natural processes which remove carbon dioxide from the atmosphere.

Explain why carbon dioxide levels have risen again over the last 150 years.

Scientists have studied the atmosphere of different planets and think that Mars is simiilar to the earth's early atmosphere.

Table 1 compares the atmosphere of Mars and Earth. 

Table 1

Suggest why the composition of gases in the Earth's atmosphere has changed from millions of years ago. 

The atmosphere of Titan, a moon of Saturn, consists of two main gases: nitrogen and methane. 

Table 2

Explain why methane falls as rain on this planet. 

UV radiation from the Sun produces alkenes, such as propene and butene, from the methane in Titan's atmosphere.

Describe a test to show that butene is an unsaturated hydrocarbon.

Give the result of the test.

This question is about the evolution of the atmosphere. 

Name two gases that account for the majority of the Earth's atmosphere. 

Explain why there is less water vapour in the atmosphere now, compared to three billion years ago. 

It is thought that the Earth's early atmosphere was similar to the atmosphere found on Venus today. 

Table 1 shows the percentages of oxygen and carbon dioxide on each planet. 

Table 1

Explain the processes that have led to the changes in oxygen and carbon dioxide levels on Earth. 

Scientists cannot be certain about the proportion of gases that made up the early atmosphere of Earth.

Why not?