C9 Chemistry of the atmosphere

• Chemistry
• Upper Secondary (Key Stage 4)
• GCSE

C9 Chemistry of the atmosphere

Name 4 gases in the Earth’s atmosphere.

1. Oxygen, nitrogen, carbon monoxide, water.
2. Oxygen, nitrogen, methane, water.
3. Oxygen, nitrogen, carbon dioxide, methane.
4. Oxygen, nitrogen, carbon dioxide, water.

Give the proportions of gases in the Earth’s atmosphere.

1. 80% Nitrogen 20% Oxygen - small % other gases
2. 80% Carbon dioxide 20% Oxygen - small % other gases
3. 80% Oxygen 20% Nitrogen - small % other gases
4. 80% Methane 20% Oxygen - small % other gases

Why is evidence for the Earth’s early atmosphere limited?

1. It has changed so much it is hard to tell
2. Scientists are just guessing
3. The timescale is so large 4.6 billion years ago
4. There is no evidence for it

How did the oceans form?

1. Ice caps melted and released water
2. Water vapour in the atmosphere condensed
3. Respiration of first plants released water
4. From water in the ground leaking out

Outcomes for today

Be able to explain how oxygen increased and carbon dioxide decreased from the early atmosphere until today's.

As organisms evolved they changed the atmosphere in a significant way. 

Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere.

1

Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.

2

Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis.

3

Oxygen increased in Earth's atmosphere due to photosynthesis by green plants and algae. 

4

Which organisms increased oxygen levels in the atmosphere?

1. Plants and animals
2. Algae and plants
3. Algae and green plants
4. Photosynthesis

How many years ago did algae start photosynthesising?

1. 2.7 million
2. 2.7 billion

Algae started photosynthesis, then about a billion years later _______ evolved.

1. Animals
2. Insects
3. Plants
4. Bacteria

Which process increased the oxygen levels in the atmosphere

1. plants and algae
2. photosynthesis

Photosynthesis word equation

Carbon dioxide + water -> oxygen + glucose

A

Symbol equation

6CO₂ + 6H₂O -> C₆H₁₂O₆ + 6O₂

B

Photosynthesis happens inside chloroplasts in the green gel like substance called chlorophyll. 

C

What are the reactants of photosynthesis?

1. Carbon dioxide and water
2. Glucose and oxygen

What are the word and symbol equations for photosynthesis?

Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis.

P

Carbon dioxide was also decreased by the formation (making) of sedimentary rocks

R

Carbon dioxide was also decreased by the formation (making) of fossil fuels

F

What effect does photosynthesis have on the amount of carbon dioxide in the atmosphere

1. Increases the amount
2. Decreases the amount

Name three ways carbon dioxide levels in the atmosphere are reduced

Which organisms increased the amount of oxygen in the Earth’s atmosphere?

Write the balanced symbol equation for photosynthesis.

When did oxygen first start appearing in the atmosphere and which organism was responsible?

Other than photosynthesis what other factors decreased the level of carbon dioxide in the atmosphere?

Describe the main changes to the atmosphere over time and the likely causes of these changes.

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