Choosing How to Separate Mixtures · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Choosing the right way to separate a mixture

Science · Matter & Materials · ages 11-13
Name ______________________   Date ____________

  1. Why does ordinary filter paper trap sand grains but let dissolved salt pass?

    • Sand dissolves before reaching the paper.
    • Sand grains are too large; dissolved salt particles fit.
    • Sand sticks because it is heavier; salt passes because it is lighter.

  2. Sand remains as solid grains in water. Which technique separates the grains while collecting the liquid?

    • Filtration through filter paper
    • Crystallisation in a dish
    • Chromatography on paper

  3. In simple distillation, the condenser turns liquid water into water vapour.

    Circle one:   True   False

  4. The chart lists separate dye spots from one sample after chromatography. Their travel distances are in cm. What is the minimum number of components detected in the sample?

    Spot A1.5Spot B3.5Spot C5.5Spot D7.5

    Answer: ______________

  5. A teacher evaporates some water from a salt solution until crystals begin to appear, then lets it cool. Which technique recovers solid crystals this way?

    • Crystallisation
    • Filtration
    • Distillation

  6. A solution contains only salt and water. Why can correctly operated simple distillation collect water separately from salt?

    • The condenser filters salt out of the vapour.
    • Heating destroys salt before vapour reaches the condenser.
    • Water vaporises; salt stays behind.

  7. Measured from the same starting line, a dye spot's centre travels 4 cm and the solvent front travels 8 cm. What is the spot's Rf value?

    Answer: ______________

  8. Tom places a chromatography starting spot below the solvent level. Ink washes into the container. Which change addresses this problem?

    • Submerge the spot.
    • Keep the spot above the solvent.
    • Let the solvent cover the starting line before adding ink.
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Choosing the right way to separate a mixture W1-mt_U_tJvy3cbB-s1

  1. Sand grains are too large; dissolved salt particles fit. · Sand grains are trapped. Much smaller dissolved salt particles pass through with water.
  2. Filtration through filter paper · Suitable filter paper traps undissolved sand while water passes through.
  3. False · A condenser cools water vapour into liquid water.
  4. 4 · Four separate spots show at least four components. Other components could overlap or remain undetected.
  5. Crystallisation · Crystallisation forms solid crystals from a solution. The crystals can be separated and dried.
  6. Water vaporises; salt stays behind. · Water vaporises at the temperatures used. Salt stays behind while the condenser collects liquid water.
  7. 0.5 · Rf = spot distance / solvent-front distance = 4 / 8 = 0.5. The units cancel.
  8. Keep the spot above the solvent. · The paper's lower edge touches solvent, but the starting spot stays above its surface.
Worksheet · LightMySky