Water
Test for water
| Test | Positive result |
|---|---|
| Cobalt(II) chloride | blue to pink |
| Copper(II) sulphate | white to blue |
Test for water purity
Heat to boiling point (pure water boils at 100 degrees celsius).
- Distilled water is used in experiments as they have the least impurities.
What is found in natural water?
- Dissolved oxygen — good for aquatic life
- Metal compounds — good for aquatic life in small amounts; some are toxic
- Plastic — can physically harm aquatic life
- Sewage — can cause disease
- Harmful microbes
- Nitrates and phosphates from fertilisers — deoxygenation of water due to eutrophication
How is water treated?
Treated water is used for drinking.
- Screen filter (large particles removed)
- Coagulate and skim off (removal of smaller insoluble particles)
- Filtration (small particles)
- Use of carbon to remove taste and odour
- Chlorination to kill pathogens/microbes
Fertilisers
Fertiliser used to improve plant growth and health:
- NPK fertilisers — Nitrogen, phosphorus, potassium for plant growth
- Ammonium (NH4+) and nitrate (NO3-) salts
Air quality and climate
Air composition
| Gas | Proportion |
|---|---|
| Nitrogen | 78% |
| Oxygen | 21% |
| CO2 | 0.04% |
| Water vapour and other noble gases | <1% |
Pollutants found in air
| Pollutant | Source | Effect |
|---|---|---|
| CO2 (also found in clean air) | Combustion | Global warming + climate change |
| CO | Incomplete combustion | Toxic gas |
| CH4 (methane) | Decomposition of vegetation; waste gases from animals | Global warming + climate change |
| Oxides of nitrogen | High temp from car engines react O2 and N2 | Acid rain, photochemical smog and respiratory issues |
| Sulphur dioxide | Sulphur impurities in crude oil and combustion of fossil fuels | Acid rain |
Greenhouse gases: CO2 and CH4
- They absorb heat energy from the earth, and re-emits it back into our atmosphere.
- Heat is trapped instead of lost into space, causing global warming.
How to reduce the effects of pollutants
- Plant trees (reduces CO2 through plants photosynthesizing)
- Reduce livestock (reduce methane)
- Decrease fossil fuel use (reduce CO2)
- Use hydrogen and renewable energy (reduce CO2)
- Flue gas desulfurization using calcium oxide (reduces creation of sulphur dioxide)
- Use catalytic converters (reverses the creation of CO and NO)
The use of catalytic converters in an engine:
2CO + 2NO → 2CO2 + N2
Photosynthesis in plants
Carbon dioxide + water → glucose + oxygen
6CO2 + 6H2O → C6H12O6 + 6O2
Conditions:
- Light
- Chlorophyll