Subscribe

9th grade · Science · Unit 7 of 10

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.

Alaska content standards learning standard: HS-PS1-2; HS-PS1-5; HS-PS1-7 · chemical reactions, reaction rates and conservation of atoms

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 Alaska

In the Alaska content standards, this is unit 7 of 10 in 9th grade Science, after The Periodic Table and before Evolution & Selection.

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: Alaska Department of Education and Early Development

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

    In CH₄ + 2O₂ → CO₂ + 2H₂O, how many oxygen atoms are on the left side (reactants)?

    answer box

  2. Question 2

    In the word equation methane + oxygen → carbon dioxide + water, which are the products?

    • methane and water
    • carbon dioxide and water
    • oxygen and carbon dioxide
    • methane and oxygen

  3. Question 3

    24 g of one substance reacts completely with 11 g of another in a closed container to form one product. What is the mass of the product?

    • 32 g
    • 40 g
    • 35 g
    • 13 g

  4. Question 4

    Which is a physical change?

    • ice melting
    • iron rusting
    • wood burning
    • milk turning sour

  5. Question 5

    What is the chemical name of NaCl?

    • sodium chlorine
    • nitrogen chloride
    • sodium chloride
    • sodium chlorate

  6. Question 6

    Which statement about a balanced chemical equation is correct?

    • The same number of molecules always appears on both sides
    • Only the reactants have atoms
    • Products always have more atoms
    • The same number of each kind of atom appears on both sides

More 9th grade