⚡ Interpreting & Interacting with Earth Systems

Question 1

What gases made up the Earth’s early atmosphere, and where did they come from?

Answer 1

Mainly carbon dioxide and water vapour, released by intense volcanic activity. Little to no oxygen was present.

Question 2

How did oxygen levels increase in the atmosphere over time?

Answer 2

Algae and plants developed and carried out photosynthesis, releasing oxygen as a by-product.

Question 3

What is the enhanced greenhouse effect, and which gases contribute most?

Answer 3

The trapping of extra heat in the atmosphere due to increased greenhouse gases like carbon dioxide and methane from human activities.

Question 4

What are the major pollutants released by burning fossil fuels, and what are their effects?

Answer 4

Carbon monoxide (toxic), sulfur dioxide (causes acid rain), and particulates (cause health problems and global dimming).

Question 5

What does “potable water” mean, and how does it differ from pure water?

Answer 5

Potable water is safe to drink but may contain dissolved minerals; pure water contains only H₂O molecules.

Question 6

What are the key stages in producing potable water from fresh water?

Answer 6

Filtration to remove solids, then sterilisation (e.g., chlorine, UV, or ozone) to kill harmful microbes.

Question 7

How is potable water obtained from seawater, and what are the challenges?

Answer 7

By desalination using distillation or reverse osmosis. It’s effective but expensive and energy-intensive.

Question 8

What are the main stages of wastewater treatment and what happens at each stage?

Answer 8

Screening: Removes large debris like leaves and twigs

Sedimentation: Solids sink to form sludge; liquid on top is effluent

Biological treatment: Bacteria break down organic matter in the effluent

Final treatment: Water may be filtered and disinfected before release or reuse

Question 9

Why must water supplies be managed sustainably, and what are some common strategies?

Answer 9

Water must be managed to avoid shortages and protect ecosystems. Strategies include:

Reducing water waste (e.g., fixing leaks)

Recycling and treating wastewater

Using water meters to reduce household use

Educating people about conservation