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7th grade · Science · Unit 10 of 10

Particles and Heat

How heating and cooling change matter

What your child practices

Solids, liquids and gases in the particle model, faster particles when heated and slower when cooled, melting, freezing, evaporation and condensation, and why mass stays the same in a phase change.

Alaska content standards learning standard: MS-PS1-4 · how adding or removing thermal energy changes particle motion, temperature and state

How we explain it

Children can open this short lesson before they practice.

  1. Solid particles vibrate in place, liquid particles slide past each other, gas particles move freely.
  2. Heating speeds particles up; cooling slows them down.
  3. Melting, freezing, evaporation and condensation change state, but the mass stays the same.

Example: Which has the fastest-moving particles: ice, water or steam? Steam is a gas. Gas particles move fastest. Answer: steam

Particles and Heat in Alaska

In the Alaska content standards, this is unit 10 of 10 in 7th grade Science, after Mixtures & Solutions.

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

    Which state of matter fills its whole container?

    • Liquid
    • Solid
    • Gas

  2. Question 2

    Which state of matter has a definite volume but no definite shape?

    • Liquid
    • Gas
    • Solid

  3. Question 3

    What happens to a liquid that is cooled enough?

    • It freezes into a solid
    • It evaporates
    • It melts

  4. Question 4

    What is melting?

    • A gas changing to a liquid
    • A liquid changing to a gas
    • A solid changing to a liquid

  5. Question 5

    All matter is made of…

    • tiny particles
    • air
    • empty space only

  6. Question 6

    A cup of water sits on a sunny windowsill. After days, there is less water. Where did it go?

    • Into the air as water vapor
    • It melted into the cup
    • It disappeared and no longer exists

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