Subscribe

8th grade · Science · Unit 6 of 16

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.

Alabama Course of Study content standard: 8.6; 8.7; 8.8 · evidence of a chemical reaction, energy released or absorbed, and conserving atoms

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 Alabama

In the Alabama Course of Study, this is unit 6 of 16 in 8th grade Science, after The Periodic Table and before Chemical Change.

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: Alabama State Department of Education (ALSDE)

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

    Substances at the start of a reaction are…

    • solvents
    • reactants
    • products
    • catalysts

  2. Question 2

    Baking soda and vinegar fizz. The bubbles are…

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

  3. Question 3

    Rust forms when iron reacts with…

    • oxygen and water
    • sugar
    • salt only
    • sunlight only

  4. Question 4

    Substances made by a reaction are…

    • products
    • reactants
    • mixtures only
    • elements only

  5. Question 5

    A chemical reaction forms…

    • nothing new
    • only a new shape
    • new substances
    • only a new state

  6. Question 6

    Which is the best evidence that sugar burning is a chemical change?

    • It melts first
    • It changes shape
    • Black carbon and gas form
    • It gets hot

More 8th grade