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7th grade · Science · Unit 2 of 18

Physical or Chemical?

Changes that make new things

What your child practices

Telling a physical change from a chemical change, spotting the signs of a new substance, and how making and throwing away everyday products affects the environment.

Texas Essential Knowledge and Skills (TEKS) teks student expectation: 7.6(C) · physical and chemical changes

How we explain it

Children can open this short lesson before they practice.

  1. A physical change alters size, shape or state, but no new substance forms.
  2. A chemical change makes a new substance. Signs: color change, gas, light, heat or a smell.
  3. Chemical changes are usually hard to reverse.

Example: Wood burns to ash and smoke. Physical or chemical change? New substances form: ash and gases. You can’t turn the ash back into wood. Answer: chemical change

Physical or Chemical? in Texas

In the Texas Essential Knowledge and Skills (TEKS), this is unit 2 of 18 in 7th grade Science, after Atoms & Elements and before Solutions & Separating.

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: Texas Education Agency (TEA)

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 is a physical change?

    • Burning a match
    • Melting an ice cube
    • Rusting a bike chain

  2. Question 2

    Baking soda and vinegar are mixed and fizz. What does this show?

    • A chemical change made a new gas
    • Nothing happened
    • Only a physical change happened

  3. Question 3

    Cutting paper into small pieces is a…

    • chemical change
    • change that makes a new substance
    • physical change

  4. Question 4

    Which change is hard to reverse?

    • Freezing water
    • Burning wood
    • Folding paper

  5. Question 5

    Ice is melted, then the water is boiled. Which statement is correct?

    • Melting is chemical and boiling is physical
    • Both are chemical changes
    • Both are physical changes

  6. Question 6

    Why is making new aluminum cans from recycled cans better for the environment than from new aluminum?

    • It uses much less energy and avoids mining
    • It uses more water and energy
    • It makes the cans heavier

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