SC21 Earth and Atmospheric Science

Question 1

Describe how the Earth’s early atmosphere was formed

Answer 1

Produced through volcanic activity, which released gases from the Earth’s interior through violent explosions. Earth’s gravity prevented the gases from escaping into outer space and they formed the atmosphere

Question 2

State the names and relative amounts of gas found in the Earth’s early atmosphere

Answer 2

• little or no oxygen
• a large amount of C02
• water vapour

Question 3

How were oceans formed?

Answer 3

When the conditions of the Earth’s surface cooled significantly,water vapour condensed and fell to the surface of the Earth, forming oceans

Question 4

How did the carbon dioxide concentration in the atmosphere decrease?

Answer 4

• CO2 is a very water soluble gas, so when the oceans formed, large amounts of condensed CO2 dissolved into the oceans
• carbonates were precipitated, which later on formed sediments on the seabed

Question 5

How did photosynthetic organisms change the composition of the atmosphere?

Answer 5

They absorbed considerable amounts of carbon dioxide through photosynthesis, and instead produced oxygen, therefore decreasing the carbon concentration and increasing the oxygen concentration

Question 6

State the chemical test for oxygen

Answer 6

Placing a glowing splint inside a test tube of gas. If oxygen is present, the splint will relight

Question 7

What is the effect of greenhouse gases?

Answer 7

• they absorb heat radiated from the Earth
• then release the energy in all directions, which keeps the Earth warm

Question 8

State the names of the main greenhouse gases

Answer 8

Carbon dioxed, water vapour and methane

Question 9

What is the greenhouse effect?

Answer 9

The retention of the sun’s infrared radiation by greenhouse gases

Question 10

Define global warming

Answer 10

The gradual warming of the Earth’s atmosphere

Question 11

What is the enhanced greenhouse effect?

Answer 11

The increase in the amount of greenhouse gases in the atmosphere is causing inbalance to the Earth’s natural conditions by trapping extra heat

Question 12

Describe how human activity increases the concentration of greenhouse gases

Answer 12

• deforestation: which reduces the amount of plants available to photosynthesise and convert the C02 into 02
• industrial revolution: which increased the amount of greenhouse gases released, causing pollution
• increased burning of fossil fuels in recent centuries

Question 13

What are the sources of carbon dioxide?

Answer 13

• combustion of wood and fossil fuels
• respiration of plants and animals
• thermal decomposition of carbonate rocks
• effects of acids on carbonates

Question 14

What are the sources of methane?

Answer 14

• digestive processes of animals
• decomposition of vegetation
• bacterial action in swamps
• rice paddy fields

Question 15

How do scientists show a causal link?

Answer 15

• collect evidence
• explain how and why correlation occurs

Question 16

What are the current effects of climate change?

Answer 16

• glaciers melting
• sea levels rising
• rainfall changing, producing floods or droughts
• habitats changing

Question 17

What is the link between carbon dioxide and global warming?

Answer 17

• There is a strong correlation between the % of carbon dioxide in the atmosphere and increased global temperatures
• the impact of this is the melting glaciers and ice caps, changing rainfall etc

Question 18

How can we reduce the impact of global warming?

Answer 18

• By using renewable energy supplies such as solar or wind to power our industries and houses rather than fossil fuels
• many nations have signed treaties aimed at reducing emissions of carbon dioxide and other gases

Question 19

How can we mitigate the effects of climate change?

Answer 19

• building flood defences to manage floods from rivers and seas
• building irrigation systems to provide water in droughts
• planting different crops, better adapted to a new climate