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9th grade · Science · Unit 8 of 28

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 GHS safety.

New York State Learning Standards learning standard: HS-PS1-2; HS-PS1-5; HS-PS1-7 · chemical reactions, what changes reaction rates, and conservation of atoms and mass

How we explain it

Children can open this short lesson before they practice.

  1. Signs of a chemical change: gas bubbles, a color change, a new solid, light or heat.
  2. In an equation, count atoms: the big number multiplies the whole formula; the small number counts one element.
  3. Mass is conserved. Read the hazard symbols on chemicals before using them.

Example: In 2H₂O, how many hydrogen atoms are there? Each H₂O has 2 hydrogen atoms. There are 2 molecules: 2 × 2 = 4. Answer: 4

Chemical Change in New York

In the New York State Learning Standards, this is unit 8 of 28 in 9th grade Science, after Electrons & Compounds and before Forces, Motion & Momentum.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: New York State Education Department (NYSED)

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

    Why should a lab never use a corrosive or an explosive chemical without checking its GHS label and Safety Data Sheet first?

    • They tell how to store, handle and respond to the hazards safely
    • They are only for adults
    • They show the price
    • They show the color of the chemical only

  2. Question 2

    20 g of one substance reacts completely with 8 g of another in a closed container to form one product. What is the mass of the product?

    • 33 g
    • 12 g
    • 28 g
    • 25 g

  3. Question 3

    What does a GHS symbol on a container warn you about?

    • how old the product is
    • the name of the store
    • a hazard of the product inside
    • the price of the product

  4. Question 4

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

    answer box

  5. Question 5

    Why does powdered sugar dissolve faster than a sugar cube?

    • Powder is a different substance
    • A cube is hotter
    • Powder has more surface area exposed to the water
    • A cube has more mass than powder

  6. Question 6

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

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

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