Grade 7 · Science · Unit 4 of 9
Particles & Mixtures
Pure substances and mixtures
What your child practises
The particle theory of matter, the states of matter, pure substances versus mixtures, and homogeneous versus heterogeneous mixtures.
New Brunswick Curriculum skill descriptor: Scientific Literacy: Sensemaking · particles and 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
Pure substance or mixture? Sort each one.
Sort into: 💎 pure substance · 🥣 mixture
- 🪴garden soil
- 🍲vegetable soup
- 💧distilled water
- 🟠a copper wire
- 🌊salt water
- 🧂pure table salt
- 🟡a gold bar
- 🌬️air
💎 pure substance: distilled water, a copper wire, pure table salt, a gold bar · 🥣 mixture: garden soil, vegetable soup, salt water, air
Hint: A pure substance is one kind of matter (an element like gold, or a compound like water). A mixture is two or more substances physically combined.
Question 2
A bottle of perfume is opened at one end of a room, and soon people at the other end can smell it. Why?
- The perfume turns into a solid
- Gas particles move randomly and spread out
- Smell particles are heavier than air
- The gas gets pushed by gravity
Gas particles move randomly and spread out
Hint: Particles of a gas move in every direction until they are spread throughout the room.
Question 3
Why can a gas be squeezed into a smaller space more easily than a liquid?
- Gas particles are not moving
- Gas particles are very small
- There are large spaces between gas particles
- Gas particles cannot touch
There are large spaces between gas particles
Hint: Particles in a liquid are already close together.
Question 4
Homogeneous or heterogeneous? Sort each mixture.
Sort into: 🥛 homogeneous (looks the same throughout) · 🍕 heterogeneous (different parts show)
- 🧂salt dissolved in water
- 🌬️air in a clean room
- 🥗a salad
- 🏖️iron filings mixed with sand
- 🍵tea with no leaves in it
- 🥣cereal in milk
🥛 homogeneous (looks the same throughout): salt dissolved in water, air in a clean room, tea with no leaves in it · 🍕 heterogeneous (different parts show): a salad, iron filings mixed with sand, cereal in milk
Hint: In a homogeneous mixture the parts are evenly mixed and look like one substance. In a heterogeneous mixture you can see different parts.
Question 5
Cooking oil and water do not stay mixed. Both are pure, but together they form…
- a homogeneous mixture
- a new pure substance
- a heterogeneous mixture
- a single element
a heterogeneous mixture
Hint: Oil floats in a separate layer, so different parts are visible.
Question 6
What is a pure substance?
- A mixture of two clean liquids
- Any clear liquid
- Any substance that is safe to drink
- Matter made of only one kind of particle
Matter made of only one kind of particle
Hint: Gold and water are pure substances because each has one kind of particle.