Water, air and environmental chemistry asks you to apply what you know about mixtures, equations and calculations to real situations: cleaning water, tracking a pollutant, following carbon, and judging a claim. The content is familiar, but the questions are written as short scenarios with data.
Check the current Cambridge IGCSE Chemistry 0620 syllabus for your exam year to confirm the exact wording of what is assessed. The lessons below teach the reasoning skills that these questions reward.
What should you know first?
You will use four earlier ideas again and again: the particle model, balanced equations, moles and relative masses, and separation methods. You do not need all of them perfectly, but you should be able to balance a short equation and find a relative formula mass.
An orienting example
Invented scenario: river water is cloudy. After it passes through a sand filter it is clear, but a few drops left to evaporate leave a white mark.
- The cloudiness was insoluble particles. They were larger than the gaps in the sand, so the filter removed them.
- The white mark shows a dissolved solid remained. Dissolved particles are as small as water particles and pass through the filter.
- So filtering removed one kind of material and left another. A statement like “the water is now pure” would be wrong.
Three short ideas, particle size, solubility and evidence, produced a full explanation. Most questions in this topic need that same pattern.
In what order should you study the lessons?
- Explain a separation step in water treatment. It gives the basic particle-size reasoning everything else depends on.
- Distinguish a dissolved substance from a suspension. It sharpens what filtering, settling and evaporating each prove.
- Interpret pollutant evidence from a supplied dataset. It adds means, percentage changes and careful conclusions.
- Trace a carbon-containing process. It brings in balanced equations and mole calculations for combustion and photosynthesis.
- Compare an environmental claim with its evidence and limits. It combines the calculation and the evaluation.
Then attempt the mixed practice set. The mole and equation-ratio tutor and the equation balance reasoning trainer help with the equation work, and the mistake log and retest queue tracks repeated slips.
What are the common traps?
- “Clear means pure.” Clear liquids can hold dissolved substances.
- “Filtering removes everything.” It removes insoluble solids only.
- “Carbon disappears when a fuel burns.” It moves into carbon dioxide, and the mass of the carbon dioxide is higher than the mass of the fuel.
- “The data proves the cause.” A pattern from one place and one day is evidence, not proof.
- Percentage slips. Divide the change by the original value, not the new one.
How should you use the practice set?
Work the questions in order on paper. Keep the answers closed until you have written a full attempt, including units. Then use the routing list at the end to send each error back to the right lesson.
The Chemistry learning guide shows where this module sits among the others. If you want a teacher to go through your reasoning question by question, our online one-to-one Chemistry tuition starts with a paid one-hour trial class.