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Grade 8 · Science · Unit 1 of 22

Mixtures, Solutions & WHMIS

Dissolving, concentration and safe handling

What your child practises

Safety symbols on hazardous products, telling pure substances, mechanical mixtures and solutions apart, what changes how fast and how much a solid dissolves, and measuring concentration in grams per 100 mL.

Alberta Curriculum learning outcome: Unit A: Mix and Flow of Matter · WHMIS symbols, pure substances, mixtures and solutions, solubility and concentration, using the particle model

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    In salt water, which part is the solute?

    • the air
    • the salt
    • the cup
    • the water
    Show answer

    the salt

    Hint: The solute is what dissolves. The solvent is the material that does the dissolving.

  2. Question 2

    Which is a solution?

    • sugar completely dissolved in water
    • oil floating on vinegar
    • sand stirred into water
    • pebbles in a bucket
    Show answer

    sugar completely dissolved in water

    Hint: A solution looks like one material because the solute is spread evenly through the solvent.

  3. Question 3

    For most solids, what usually happens to solubility when the water is heated?

    • Nothing dissolves.
    • The solute turns into a gas.
    • Less solute can dissolve.
    • More solute can dissolve.
    Show answer

    More solute can dissolve.

    Hint: Warm water can usually hold more dissolved solid than cold water.

  4. Question 4

    Which change speeds up how fast sugar dissolves in water?

    • using a bigger cup
    • using bigger lumps of sugar
    • stirring
    • cooling the water
    Show answer

    stirring

    Hint: Stirring brings fresh solvent to the solute. Smaller pieces and warmer water also help.

  5. Question 5

    A student crushes a sugar cube before adding it to water. What does this change?

    • The sugar can never dissolve.
    • The sugar changes into salt.
    • The sugar dissolves faster because there is more surface touching the water.
    • The water gets heavier.
    Show answer

    The sugar dissolves faster because there is more surface touching the water.

    Hint: Smaller particles give the solvent more surface to work on.

  6. Question 6

    A solution has 24 g of sugar dissolved in 200 mL of solution. What is the concentration, in g per 100 mL?

    answer boxg/100 mL

    Show answer

    12 g/100 mL

    Hint: Divide by the volume, then scale to 100 mL: 24 ÷ 200 × 100 = 12 g/100 mL.

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