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Year 10 Science — Mixtures, concentration and separation

Tell solutions, suspensions and colloids apart, work out a concentration as a percentage, and choose the right method for pulling a given mixture apart.

Name: ________________________

Before you start

Three beakers, and what the laser beam does in each of them.

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  1. 1. Salt in water — the beam crosses unseen
  2. 2. Chalk powder in water — the beam shows, and the powder settles
  3. 3. Milk in water — the beam shows, and nothing settles

Shine the light in from the side and watch from a right angle. The path you can see is light being scattered off particles big enough to scatter it.

  1. 1.A black ink spot is put on a paper strip and the strip is dipped so the water level starts below the spot. The water rises and the spot spreads into several coloured bands. Why do the bands separate?

    • a) The heavier colours sink while the lighter ones rise
    • b) The paper reacts with each colour to make a new one
    • c) Water dissolves some colours and destroys the others
    • d) The components travel up the paper at different speeds

  2. 2.A mixture of crushed camphor and sand is heated gently under an inverted funnel, and a white solid appears on the inside of the funnel. What has happened?

    • a) The camphor turned straight to vapour and then back to solid, while the sand stayed put
    • b) The two solids reacted to make a new white compound
    • c) The sand melted and rose as a vapour, leaving the camphor behind
    • d) The camphor melted, boiled and then condensed as a liquid

  3. 3.Put the steps of growing copper sulfate crystals in order, starting from Warm the water with the solid, stirring, until no more will dissolve.

    • Filter off the crystals and rinse them with cold water
    • Cover the filtrate and leave it to cool slowly, undisturbed
    • Leave the crystals to dry on a watch glass
    • Warm the water with the solid, stirring, until no more will dissolve
    • Filter the hot saturated solution to take out insoluble impurities

  4. 4.25 mL of juice concentrate is made up with water to 250 mL of drink. What is the volume by volume percentage of concentrate? Answer with a number.

  5. 5.Muddy water stays cloudy after filtering. Powdered alum is stirred in and the water clears. What did the alum do?

    • a) Made the fine particles clump together into lumps heavy enough to settle
    • b) Dissolved the mud particles so they were no longer there
    • c) Turned the suspension into a true solution
    • d) Boiled off the water that was holding the mud up

  6. 6.Sort each description by the kind of mixture it belongs to.

    Groups: Solution · Colloid · Suspension

    • Lets a laser beam through with no visible path
    • Particles between 1 and 1000 nanometres
    • Particles smaller than 1 nanometre
    • Particles you can see, which settle when left alone
    • Scatters a light beam and yet stays evenly spread
    • Particles larger than 1000 nanometres

  7. 7.Match each separation method to the mixture it is meant for.

    • Distillation
    • Separating funnel
    • Sublimation
    • Paper chromatography
    • Centrifugation
    • A solid that sublimes mixed with one that does not
    • Heavier particles from a lighter liquid
    • Two immiscible liquids
    • The coloured components of an ink or a dye
    • Two miscible liquids with different boiling points

  8. 8.8 g of glucose is dissolved in water and made up to 200 mL of solution. What is the mass by volume percentage? Answer with a number.

Answer key — Year 10 Science — Mixtures, concentration and separation

  1. 1. d) The components travel up the paper at different speeds
  2. 2. a) The camphor turned straight to vapour and then back to solid, while the sand stayed put
  3. 3. 1. Warm the water with the solid, stirring, until no more will dissolve 2. Filter the hot saturated solution to take out insoluble impurities 3. Cover the filtrate and leave it to cool slowly, undisturbed 4. Filter off the crystals and rinse them with cold water 5. Leave the crystals to dry on a watch glass
  4. 4. 10
  5. 5. a) Made the fine particles clump together into lumps heavy enough to settle
  6. 6. Particles smaller than 1 nanometre → Solution; Lets a laser beam through with no visible path → Solution; Particles between 1 and 1000 nanometres → Colloid; Scatters a light beam and yet stays evenly spread → Colloid; Particles larger than 1000 nanometres → Suspension; Particles you can see, which settle when left alone → Suspension
  7. 7. Distillation → Two miscible liquids with different boiling points; Separating funnel → Two immiscible liquids; Sublimation → A solid that sublimes mixed with one that does not; Paper chromatography → The coloured components of an ink or a dye; Centrifugation → Heavier particles from a lighter liquid
  8. 8. 4