Grade 7 · Science · Unit 6 of 12
Solutions & Separating
Dissolving and splitting mixtures
What your child practises
Solutes, solvents and solubility, what makes things dissolve faster, saturated and unsaturated solutions, concentration, why water is called the universal solvent, ways to separate mixtures, and some environmental effects of industrial separation.
Ontario Curriculum expectation: C1.2, C2.4–C2.7 · solubility, concentration, water as a solvent, and separating mixtures
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
Which will NOT dissolve in water?
- sugar
- cooking oil
- salt
- food colouring
Show answer
cooking oil
Hint: Oil floats in a separate layer instead of mixing.
Question 2
Which method best separates each mixture?
Sort into: ☕ filter · ♨️ evaporate · 🧲 magnet
- 🍵tea leaves in water
- 🧂salt dissolved in water (to collect the salt)
- ☕coffee grounds in water
- 🔩iron nails mixed with plastic beads
- 🏖️iron filings mixed with sand
- 🌊sea water (to collect sea salt)
Show answer
☕ filter: tea leaves in water, coffee grounds in water · ♨️ evaporate: salt dissolved in water (to collect the salt), sea water (to collect sea salt) · 🧲 magnet: iron nails mixed with plastic beads, iron filings mixed with sand
Hint: Filter a solid out of a liquid it has not dissolved in. Evaporate the water to get back a dissolved solid. Use a magnet to pull out iron or steel.
Question 3
What does saturated mean?
- The solution is very cold
- The solvent has been removed
- No more solute can dissolve at that temperature
- There is no solute in the water
Show answer
No more solute can dissolve at that temperature
Hint: A saturated solution is full.
Question 4
A 300 mL sample of a sugar solution contains 18 g of sugar. How many grams of sugar are in each 100 mL?
answer boxg
Show answer
6 g
Hint: Divide the mass by the number of 100 mL portions: 18 ÷ 3.
Question 5
A sand filter at a water treatment plant mainly removes…
- all dissolved gases
- small undissolved particles
- dissolved salt
- all colours from the water
Show answer
small undissolved particles
Hint: Filtering catches undissolved particles. Dissolved substances pass through.
Question 6
Warm cola loses its fizz faster than cold cola. What does this suggest about gases in liquids?
- Temperature has no effect on gases
- Gases are more soluble in warmer liquids
- Gases are less soluble in warmer liquids
- Gases cannot dissolve in liquids
Show answer
Gases are less soluble in warmer liquids
Hint: The warmer liquid holds less dissolved carbon dioxide, so bubbles escape.