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Grade 8 Science — Solutes, solvents and solutions

Name the solute and the solvent in a solution, tell a saturated solution from an unsaturated one, and say how temperature changes what will dissolve.

Name: ________________________

  1. 1.For most solids dissolving in a liquid, what does raising the temperature do to the solubility?

    • a) It increases it for salts and decreases it for sugars
    • b) It leaves it unchanged
    • c) It decreases it
    • d) It increases it

  2. 2.The greatest amount of solute a fixed quantity of solvent will dissolve at a particular temperature has a one-word name. What is it?

  3. 3.Match each word to what it names.

    • Solute
    • Solvent
    • Solution
    • Solubility
    • the substance that does the dissolving
    • the substance that dissolves
    • the most solute a fixed quantity of solvent will take at a given temperature
    • the uniform mixture the two of them make

  4. 4.Which is the more concentrated solution: 2 spoons of salt in 100 mL of water, or 4 spoons in 50 mL?

    • a) Neither, because concentration applies to gases rather than solids
    • b) 4 spoons in 50 mL, since more solute sits in less solution
    • c) They are equally concentrated, since both use salt and water
    • d) 2 spoons in 100 mL, since there is more water to spread through

  5. 5.Which statement about a saturated solution is the right one?

    • a) It has dissolved less solute than an unsaturated solution
    • b) It can still dissolve more solute at that temperature
    • c) No more solute can be dissolved into it at that temperature
    • d) It forms at high temperatures and nowhere else

  6. 6.Each sip of a homemade oral rehydration solution tastes the same as the last. Why?

    • a) The sugar and salt cancel out each other's taste
    • b) The water dilutes both of them until neither can be tasted
    • c) The sugar and salt are evenly distributed through the whole of the water
    • d) The sugar settles at the bottom and the salt stays at the top

  7. 7.Gases behave the other way round from solids. What happens to the solubility of a gas in water as the water warms up?

    • a) It decreases
    • b) It stays the same
    • c) It increases
    • d) It increases up to 50 °C and decreases after that

  8. 8.Spoons of salt are stirred into a glass of water one after another. Put the four stages back into order.

    • A spoon is added that does not fully dissolve
    • The undissolved salt settles at the bottom
    • More spoons go in and still dissolve
    • The first spoon of salt dissolves completely

Answer key — Grade 8 Science — Solutes, solvents and solutions

  1. 1. d) It increases it
  2. 2. solubility
  3. 3. Solute → the substance that dissolves; Solvent → the substance that does the dissolving; Solution → the uniform mixture the two of them make; Solubility → the most solute a fixed quantity of solvent will take at a given temperature
  4. 4. b) 4 spoons in 50 mL, since more solute sits in less solution
  5. 5. c) No more solute can be dissolved into it at that temperature
  6. 6. c) The sugar and salt are evenly distributed through the whole of the water
  7. 7. a) It decreases
  8. 8. 1. The first spoon of salt dissolves completely 2. More spoons go in and still dissolve 3. A spoon is added that does not fully dissolve 4. The undissolved salt settles at the bottom