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7th grade · Science · Unit 7 of 10

Chemical Reactions

New substances form, and atoms are conserved.

What your child practices

Practices signs of chemical reactions, how properties change when new substances form, conservation of mass, and devices that release or absorb thermal energy through reactions.

Maine Learning Results learning standard: MS-PS1-2; MS-PS1-5; MS-PS1-6 · properties change in chemical reactions, atoms are conserved, and reactions can release or absorb energy

How we explain it

Children can open this short lesson before they practice.

  1. Signs of a chemical reaction: a new color, gas bubbles, a new solid, light, or heat given off or taken in.
  2. Reactants are what you start with; products are the new substances made.
  3. Atoms are only rearranged, so the total mass stays the same.

Example: 20 g of reactants react in a sealed bag. What is the mass of the products? No atoms are lost or gained. Mass is conserved. Answer: 20 g

Chemical Reactions in Maine

In the Maine Learning Results, this is unit 7 of 10 in 7th grade Science, after How Plants Work and before Earth's Moving Surface.

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: Maine Department of Education

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 property could show a new substance formed?

    • A different container
    • A different melting point
    • A different amount
    • A different shape

  2. Question 2

    An endothermic reaction…

    • releases thermal energy
    • absorbs thermal energy
    • has no products
    • makes light only

  3. Question 3

    Baking soda and vinegar fizz. The bubbles are…

    • air from the room
    • oxygen from the sun
    • carbon dioxide gas
    • water vapor only

  4. Question 4

    Which is a sign of a chemical reaction?

    • Paper is cut
    • Ice melts
    • A gas forms
    • Water is poured

  5. Question 5

    Which is a physical change?

    • Baking a cake
    • Burning wood
    • Rusting iron
    • Melting butter

  6. Question 6

    A reaction in a sealed bag makes gas and the bag puffs up. The mass of the bag…

    • decreases
    • becomes zero
    • increases
    • stays the same

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