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6th grade · Science · Unit 1 of 9

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.

Arizona Academic Standards learning standard: 6.P1U1.1; 6.P1U1.2 · how particle motion, temperature and pressure explain changes of state

How we explain it

Children can open this short lesson before they practice.

  1. Matter is made of particles that attract each other.
  2. Solid: strongest attraction and a fixed shape. Liquid: definite volume, no definite shape.
  3. Gas: weakest attraction, so it fills its whole container. Water vapor is water as a gas.
  4. Heating makes particles move faster and spread out; cooling slows them.

Example: Which state has a definite volume but takes the shape of its container? A solid keeps its shape. A gas fills any container. A liquid keeps its volume but flows. Answer: liquid

Particles and Heat in Arizona

In the Arizona Academic Standards, this is unit 1 of 9 in 6th grade Science, before Atoms & Elements.

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: Arizona 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

    Butter left on a warm counter gets soft and runny. What is happening?

    • Heated particles move faster, so the solid is starting to melt
    • The particles are disappearing
    • The butter is freezing

  2. Question 2

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

    • Solid
    • Gas
    • Liquid

  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 happens to the particles of a substance when it is heated?

    • They stop moving
    • They disappear
    • They move faster

  5. Question 5

    What is a phase change?

    • A change in size only
    • A change in color only
    • A change from one state of matter to another

  6. Question 6

    Why does water vapor form drops on the cold bathroom mirror?

    • The mirror makes water
    • The vapor freezes into ice
    • The vapor loses heat and condenses into liquid

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