1. Part 1: Substances Exam Questions
Lifestyle Chemistry
Part 1: Substances
Exam Questions

2. The diagram shows the cleaning instructions on a paint tin.
Based on the information given on the label, what is the solvent used in this paint?
(A) Alcohol
(B) Detergent
(C) Soap
(D) Water

3. D
If water will clean the brushes, then water must be the solvent for this paint. Alcohol and water will mix so alcohol may dissolve this paint but if alcohol had been used to make it, alcohol would have been suggested to clean it, thus A is incorrect. Soap and detergent are both surfactants and solvents, so B and C are both incorrect.

5. A
An emulsion is a stable mixture of two liquids in which one does not dissolve in the other, as the liquids stay mixed for a long time without separating into layers. So A is the answer. A foam is a mixture of a gas and a liquid so B is incorrect. A solution is a mixture in which one component has dissolved in the other, so C is incorrect. A suspension has non-settling solid particles in a liquid or gas so D is incorrect.

7. C
Surface tension causes the water to form droplets on the leaf as in diagram 2. Surface tension allows the steel needle to float on the water as in diagram 3. Therefore C is the answer The buoyancy of the duck allows it to swim with part of its body above the surface in diagram 1. The food dye is spreading through the water by diffusion in diagram 4. So A, B and D are incorrect.

8. The instructions on the label of a medicine bottle state: ‘Shake well before use’.
Based on the instructions given on the label, what type of substance is this medicine?
(A) Colloid
(B) Cosmetic
(C) Solution
(D) Suspension

9. D
A suspension is a mixture of fine particles suspended in a liquid. These particles settle out to form separate layers but can be shaken back into a suspension.

11. C
This phenomenon is surface tension. It occurs at the surface of water where it is in contact with air. Where water is in contact with its container, forces between water molecules are to some extent balanced by forces between water molecules and the atoms or molecules of the container. Thus surface tension is not responsible for water taking the shape of its container, so A is incorrect. Most alcohol compounds are not soluble in water, so B is incorrect. The ability of some light-weight insects and spiders to walk on water is because the weight force acting through their feet is not great enough to overcome the surface tension so, C is the answer. The shape of the meniscus depends on forces between the water and container and does not depend on the depth of the water so D is incorrect.

13. B
The salad dressing contains floating pieces of onion that are not dissolved, so C is incorrect. Rather, the onion pieces are suspended in the mixture, as in A or B. Vinegar will completely mix with water and salt will usually dissolve in water so D is incorrect. Water is a solvent, not a solute and vinegar always mixes with water so it does not form a colloid in water, so A is incorrect. Vinegar is a water solution, so salt can dissolve in vinegar. Salad dressing is an “oil in water” colloid because the proportion of oil is small compared to the amount of water solution. Thus B is correct.

15. B
A foam colloid has a gas dispersed through a liquid so B is the answer. Gases are completely miscible with one another and therefore cannot be a colloid. So A is incorrect. A liquid dispersed through a liquid (as in mayo or cream) is an emulsion, not a foam so C is incorrect. A solid dispersed through a liquid (paint) is not a foam so D is incorrect.

17. D
The mixture shows two phases so it is neither a solution nor a solvent as both of these would be homogeneous. Thus B and C are incorrect. A colloid has very small particles that remain dispersed throughout a liquid phase so A is incorrect. The mixture is a suspension because the particles settle out towards the bottom over a period of time. Thus D is correct.

19. D
A solution is a completely homogeneous (uniform) mixture in which one substance (a solute) is completely dissolved in a liquid (the solvent). There are no particles to settle out or to be filtered out. As there are no particles, light passes through a solution without scattering. Thus D is the only possible answer.

21. B
The water drop has flattened, round shape. This is due to the surface tension in water acting at right angles to the surface and making the water drop rounded. The effect of gravity flattens it out slightly. Thus B is the answer. Air pressure and gravity both tend to flatten out the drop and so the water drop would not be rounded by these factors. So A is incorrect. Water pressure will act on the glass surface and air pressure will act on the upper surface of the droplet. So neither C or D have two factors affecting the shape of the droplet and therefore are incorrect.

23. C
Salad dressing is a suspension as it contains herbs, spices and oil droplets suspended in an acidic aqueous layer. Whisking eggs incorporates air into the liquid egg white, so it is a foam. Mayonnaise is a stable emulsion of oil and aqueous layers. Only C has this combination listed correctly.

25. D
Whipped cream is a mixture of a gas in a liquid. The liquid cream has been beaten or whisked to incorporate air (gas) into the mixture to form a “foam” colloid. So D is the answer.

27. C
The meniscus for X is turned upwards, so the adhesive forces are stronger than the surface tension. Thus C is the answer. The meniscus for Y is flat so the adhesive forces are similar to the surface tension. Thus A is wrong. The meniscus for Z is convex, so the adhesive forces are less than the surface the surface tension. Thus B is incorrect. The shape of the meniscus depends on the relative strength of the adhesive forces compared to the surface tension so D is incorrect.

29. C
The shape of the meniscus is determined by the relative strength of the inter-particle forces within each liquid compared to the forces between the liquid particles and the particles of the glass walls of the test tube. The inter-particle forces within a liquid create the surface tension of that liquid. If the surface tension of the liquid is greater than the liquid particle to glass forces, the edges of the liquid will turn downwards, whereas if the surface tension was smaller, the edges will turn upwards. The water meniscus is turned up at the outer edge, so D is incorrect. The mercury meniscus is turned down at the outer edge so C is correct. This experiment does not give information about the relative strengths of the surface tension of water and mercury so A and B are not possible answers.

30. Explain ONE advantage of a colloid compared to another type of suspension. In your answer, refer to a specific colloid.

31. Explain ONE advantage of a colloid compared to another type of suspension. In your answer, refer to a specific colloid.

32. In a colloid such as mayonnaise, the particles are small and remain evenly dispersed and do not settle out, so a colloid does not need to be shaken or stirred. In a suspension, such as orange juice, the particles are lager and settle out to the bottom of the liquid however and so it must be shaken before drinking.

35. It is poisonous and if swallowed, could cause illness or death.
Call for advice from a doctor or the Poisons Information Centre and follow their instructions. D not induce vomiting unless instructed. Keep the child calm.

37. Remove dirt, oil/fat and/or grease from surfaces
Avoid getting detergent in eyes
Detergents
Avoid inhaling or having contact of the solvent with skin
Dissolves other substances
Solvents (Organic)

38. (a) What is the difference between a colloid and a suspension? 2
(b) What type of mixture is mayonnaise? 1
(c) What is ONE advantage of mayonnaise being this type of mixture? 1

40. A suspension is a mixture of fine, solid particles suspended in a liquid, whereas a colloid’s particles and medium may be solid, liquid or gas. The ingredients in a suspension settle out into layers quickly, whereas the particles usually remain suspended for longer periods of time in colloids. The dispersed particles may be filtered out of a suspension, but can not be filters out of a colloid.
Mayonnaise is an emulsion (type of colloid)
It does not separate on standing do does not need to be shaken before use OR The texture and appearance is more appealing to consumers than if it were a suspension.

42. a)

43. b)

44. b) It is a suspension, because the chemical settled over time and increasingly allowed light to pass through the water and reach the sensor.