Pure substances and mixtures, elements and compounds, atoms and molecules, and the difference between solutions, suspensions and colloids, including the types of solution.
4 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
Air, sea water and milk look uniform, yet each is a mixture of different substances. How can we tell a mixture from a pure substance?
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Copy these into your notebook in your own words — that is how they stick.
One kind of atom; cannot be broken down chemically.
Elements chemically combined in a fixed ratio; different properties.
Substances not combined; variable composition; separated by physical means.
Sharp melting and boiling points.
Solute dissolved in solvent; tiny particles; transparent; does not settle.
Large particles; cloudy; settles; filtered out.
Medium particles; does not settle; scatters light (Tyndall effect).
Solid/liquid/gas in liquid, solid in solid (alloy), gas in gas (air).
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness. More games in the Chemistry Arcade.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.
Write full answers, then reveal the mark scheme and tick the points you earned (15 marks in total). Show all your working — method marks count. Your answers are saved on this device.
Question 1 [15 marks]
A student has samples of sea water, distilled water, magnesium and muddy water.
(a) (a) Classify each sample as an element, a compound or a mixture. [4]
(b) (b) State two differences between a compound and a mixture. [2]
(c) (c) Describe how the student could show that the distilled water is pure. [2]
(d) (d) Name the type of mixture muddy water is and give two properties. [3]
(e) (e) Distinguish between a solution and a colloid. [2]
(f) (f) Give one example of a gas-in-liquid solution and one of a solid-in-solid solution. [2]
Find these in your own past-paper booklets for extra timed practice. Items above are written in the style of these papers; any adapted from a specific question say so.