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Grade 9 · Science · Unit 5 of 10

Chemical Change

Reactions, mass and chemical names

What your child practises

Telling a chemical change from a physical change, reading simple word and symbol equations, why mass is conserved, what speeds a reaction up, exothermic and endothermic changes, and WHMIS safety.

Alberta Curriculum learning outcome: Unit B: Matter and Chemical Change · evidence of chemical change, reactants and products, conservation of mass, reaction rates and names of simple compounds

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

    Which two things must be present for a fuel to burn (combustion)?

    • helium and light
    • carbon dioxide and ice
    • oxygen and heat (a high enough temperature)
    • nitrogen and water
    Show answer

    oxygen and heat (a high enough temperature)

    Hint: Fire needs fuel, oxygen and heat. Taking away any one of them puts it out.

  2. Question 2

    What does the law of conservation of mass say?

    • Products always have more mass
    • Mass can be created by heat
    • The total mass of the reactants equals the total mass of the products
    • Mass is lost when a gas forms
    Show answer

    The total mass of the reactants equals the total mass of the products

    Hint: Atoms are rearranged in a reaction, not made or destroyed.

  3. Question 3

    Rusting of iron needs which substances?

    • helium and sand
    • oxygen and water
    • only carbon dioxide
    • only nitrogen
    Show answer

    oxygen and water

    Hint: Iron, oxygen and water react to make iron oxide (rust). Painting or oiling iron keeps oxygen and water away.

  4. Question 4

    In 2H₂ + O₂ → 2H₂O, how many oxygen atoms are on the left side (reactants)?

    answer box

    Show answer

    2

    Hint: One O₂ molecule has 2 oxygen atoms.

  5. Question 5

    36 g of one substance reacts completely with 7 g of another in a closed container to form one product. What is the mass of the product?

    • 48 g
    • 40 g
    • 43 g
    • 29 g
    Show answer

    43 g

    Hint: Mass is conserved, so the product has the same total mass as the reactants: 36 + 7 = 43 g.

  6. Question 6

    In a chemical reaction, what are the reactants?

    • the container
    • the starting substances
    • the energy released
    • the new substances formed
    Show answer

    the starting substances

    Hint: Reactants are what you start with. Products are what you end up with.

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