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9th grade · Science · Unit 7 of 11

Chemical Change

Reactions, mass and chemical names

What your child practices

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.

California Content Standards learning standard: HS-PS1-2; HS-PS1-5; HS-PS1-7 · chemical reactions, reaction rates and conservation of atoms

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

  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

  3. Question 3

    Rusting of iron needs which substances?

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

  4. Question 4

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

    answer box

  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

  6. Question 6

    In a chemical reaction, what are the reactants?

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

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