Topic 1 - The Earths Sea And Atmosphere

Question 1

What was the Earth like 4.5 Billion Years Ago?

Answer 1

• Earth first formed due to volcanoes erupting,
• Thin crust formed
• Atmosphere formed from volcanic gases: CO₂ & water vapour, with small amounts of ammonia (NH₃) & Methane (CH₄) & Nitrogen (N₂)

Question 2

What was the Earth like 3 Billion years ago?

Answer 2

• Earth had started cooling down enough for water vapour to condense and form oceans
• CO₂ was main gas
• Simple plants evolved and through photosynthesis they took in CO₂ and produced O₂ into the atmosphere

Question 3

What was the Earth like 1 billion year ago?

Answer 3

• Excess O₂ reacted in the presence of UV light to form the OZone (O₃)
• The OZone filtered out most of the damaging UV light and so more complicated life forms evolved
• Very little CO₂ left

Question 4

How was CO₂ removed from the atmosphere?

Answer 4

• Dissolved in oceans
• Animals used it to make carbonate shells
• When animals died the shell fell to the bottom of the ocean and became sediment, eventually turning into sedimentary rock

Question 5

What is the Earths atmosphere like in Present time?

Answer 5

Dry air is :

• 78% Nitrogen (N₂)
• 21% Oxygen (O₂)
• 0.9% Argon
• 0.04% Carbon dioxide (CO₂)
• and small traces of other gases

Question 6

How is the atmosphere still changing due to Human Activity?

Answer 6

• Burning fossil fuels = releases CO₂ , (more fossil fuels burnt for growing population)
• Deforestation = Increases in CO₂, (less trees more CO2 in atmosphere)
• Livestock Farming = releases CH₄ from animals

Question 7

How is the atmosphere still changing due to Volcanic Activity?

Answer 7

• Sulphur Dioxide (SO₂) = Volcanoes release it high up into the atmosphere when erupting
• Carbon Dioxide (CO₂)= released in volcanic eruptions

Question 8

Why can’t we be precise about the early atmosphere?

Answer 8

As nobody was there/ alive and there are no written records or documents to prove it

Question 9

How can you investigate the proportion of O₂ in the atmosphere?

Answer 9

1. Copper (Cu) reacts with Oxygen (O₂) to make copper oxide (CuO) - shows O₂ is used up
2. Pass a fixed amount of air through two syringes over heated copper
3. Start with 100cm³ of air you’ll finish with 79cm³ showing that 21cm³ of air is O₂ which is 20%
4. Copper will turn jet black when there has been a reaction

Question 10

What is the word and symbol equation for investigation O₂ in the atmosphere?

Answer 10

• Copper + oxygen = copperoxide
• 2Cu + O2 = 2CuO