C1.1 The Earth's sea and atmosphere

Question 1

What is an atmosphere?

Answer 1

The layer of gas surrounding a planet

Question 2

What do volcanoes on Earth release?

Answer 2

• carbon dioxide
• water
• ammonia
• methane
• nitrogen

Question 3

Why do scientists believe that there was little or no oxygen in the early atmosphere of Earth?

Answer 3

• volcanoes don’t release oxygen

- iron compounds found in the Earth’s oldest rocks would only form in the absence of oxygen

Question 4

How do scientists think oceans formed?

Answer 4

They think that the Earth got colder as it got older, so water vapour in the hot atmosphere condensed to form oceans

Question 5

How was carbon dioxide in the early atmosphere reduced?

Answer 5

• it dissolved into the oceans
• some marine orgamisms used dissolved carbon dioxide to make their shells
• the production of limestone

Question 6

What type of rock is limestone?

Answer 6

Sedimentary

Question 7

What compound is limestone made from?

Answer 7

Calcium carbonate

Question 8

How is limestone produced?

Answer 8

• marine organisms die
• their shells and skeletons fall and become sediment
• layers of sediment build up over millions of years and become limestone

Question 9

When do scientists believe life started on Earth?

Answer 9

4 billion years ago

Question 10

When do scientists believe some organisms developed the ability to photosynthesise?

Answer 10

1 billion years ago

Question 11

How did the amount of oxygen in the Earth’s early atmosphere gradually increase?

Answer 11

More photosynthesising organisms evolved which meant that the rate at which carbon dioxide was removed and oxygen was added increased

Question 12

What percentage of dry air is nitrogen?

Answer 12

78%

Question 13

What percentage of dry air is oxygen?

Answer 13

21%

Question 14

What percentage of dry air is argon?

Answer 14

0.9%

Question 15

What percentage of dry air is carbon dioxide?

Answer 15

0.04%

Question 16

What causes variations in the amounts of gases within the Earth’s atmosphere?

Answer 16

• natural causes
• deforestation
• the burning of fossil fuels
• cattle and rice fields

Question 17

How do natural causes cause variations in the amounts of gases in the Earth’s atmosphere?

Answer 17

• volcanoes release large amounts of sulphur dioxide

- lightning can produce nitrogen oxides

Question 18

What compounds does the burning of fossil fuels release?

Answer 18

• carbon dioxide
• carbon monoxide
• sulphur dioxide

Question 19

How do cattle and rice fields cause changes in the amounts of gases in the Earth’s atmosphere?

Answer 19

They release large quantities of methane

Question 20

How does deforestation cause changes to the amounts of gases in the Earth’s atmosphere?

Answer 20

It means there are fewer trees to remove carbon dioxide and produce oxygen