Chemistry in everyday life, industry and the environment
Domain 8 - keemia igapäevaelus, tööstuses ja keskkonnas - connects reactions to Estonian fuels, drinking water, air quality, materials and waste. Questions ask you to name a substance, explain a process, or evaluate an environmental claim.
Air, fuels, energy
- Air by volume: about 78 % N₂, 21 % O₂, 0.9 % Ar, 0.04 % CO₂. Pollutants: CO, SO₂, NOₓ, soot, unburnt hydrocarbons.
- Estonia's main fuel is oil shale (põlevkivi), burned in the Narva power plants and processed into shale oil and chemicals; wood, peat and natural gas are also used.
- Complete combustion gives CO₂ and H₂O; too little oxygen gives CO, which binds haemoglobin and is deadly, plus soot.
- CO₂ and CH₄ are greenhouse gases; SO₂ and NOₓ form acid rain (H₂SO₃, H₂SO₄, HNO₃), which leaches soil nutrients and corrodes limestone.
- Catalytic converters oxidise CO and hydrocarbons and reduce NOₓ; limestone slurry removes SO₂ from flue gas.
Water and materials
- Drinking water is treated by settling, filtration, aeration and chlorination or ozonation; hard water contains Ca²⁺ and Mg²⁺ and forms scale.
- Limestone (CaCO₃) gives lime, cement and glass; clays give ceramics; ores are reduced to metals; fertilisers supply N, P and K.
Waste
- Sorting: paper, glass, plastic, metal, biowaste, hazardous waste. Recycling aluminium saves about 95 % of the energy needed from ore.
Worked example
Explain with equations why burning high-sulphur oil shale makes rain more acidic. Sulphur in the fuel burns: S + O₂ → SO₂. In the plume SO₂ is oxidised to SO₃, which with water gives H₂SO₄: SO₃ + H₂O → H₂SO₄. The extra H⁺ lowers the pH of rain below the natural 5.6 set by dissolved CO₂, dissolving limestone (CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂) and damaging forests. Remedies: lower-sulphur fuel, limestone added to the boiler, flue-gas desulphurisation.
Traps that cost marks
- Confusing CO (toxic) with CO₂ (greenhouse gas).
- Calling hard water polluted - calcium and magnesium are natural.
- Saying burning produces only CO₂ regardless of the oxygen supply.
- Writing that acid rain is caused by CO₂ alone.
Experimental skills and safety
Domain 9 - katseline töö ja ohutus - is marked on procedure, observation and conclusion. The examiner looks for correct apparatus, safe handling, an observation that is not an interpretation, and a conclusion tied to the evidence.
Safety rules
- Goggles on; no eating, drinking or tasting; never point a test tube at anyone; heat at an angle, moving the tube through the flame.
- Diluting sulphuric acid: pour acid slowly into water and stir - never water into acid, because the mixture can boil and spit.
- Waft vapours toward your nose; do not sniff directly. Return unused chemicals; never pour them back into the reagent bottle.
- Learn the GHS pictograms: flame, corrosive, toxic, oxidising, environmental hazard.
Apparatus and measurement
- Measure volumes with a measuring cylinder (rough) or pipette/burette (precise), reading the bottom of the meniscus at eye level; use a balance reading to 0.01 g for masses.
- Heat with a spirit burner or hotplate, tripod and gauze; evaporate in an evaporating dish, not a test tube.
- Test gases: hydrogen pops with a burning splint; oxygen relights a glowing splint; carbon dioxide turns limewater milky (Ca(OH)₂ + CO₂ → CaCO₃ + H₂O).
Observations and conclusions
- Record observations, not explanations: 'white precipitate formed', 'solution turned blue', 'temperature rose 4 °C', 'gas bubbles'. Interpretation belongs in the conclusion.
- A fair test changes one variable, keeps others constant and repeats measurements; the conclusion must state whether the hypothesis was supported and cite the data.
Worked example
Does temperature affect how fast sugar dissolves? Hypothesis: hotter water dissolves sugar faster. Method: 100 cm³ of water at 20, 40 and 60 °C, 5 g of sugar each, same stirring, stopwatch until no crystals remain. Results: 120 s, 65 s, 30 s. Conclusion: the hypothesis is supported - raising the temperature shortens the dissolving time, because warmer water molecules move faster. Report the trend, not a single trial, and name the controlled variables.
Traps that cost marks
- Writing 'it reacted' or 'it burned' instead of what you actually saw.
- A conclusion with no reference to the data.
- Describing unsafe steps such as tasting a chemical or heating a closed system.