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8th grade · Science · Unit 3 of 16

Particles & Matter

Kinetic theory and the atom

What your child practices

How the movement of particles explains solids, liquids and gases and changes of state, the parts of an atom (including the quarks inside protons and neutrons, and electrons as leptons), elements and compounds, and telling physical from chemical changes.

Alabama Course of Study content standard: 8.2 · 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. Particles in solids vibrate in place; in liquids they slide; in gases they move freely.
  2. Melting, freezing, evaporation and condensation are changes of state. Condensation is gas to liquid.
  3. Atoms have protons and neutrons (made of quarks) in the nucleus, with electrons around it. An element has one kind of atom.

Example: Water droplets form on a cold glass. Which change of state is this? Water vapor in the air touches the cold glass. Gas becomes liquid. Answer: condensation

Particles & Matter in Alabama

In the Alabama Course of Study, this is unit 3 of 16 in 8th grade Science, after Density & Buoyancy and 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: 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

    Melting is when a…

    • liquid changes to a gas
    • gas changes to a liquid
    • liquid changes to a solid
    • solid changes to a liquid

  2. Question 2

    Which is a chemical change?

    • Water freezing
    • Sugar dissolving
    • Iron rusting
    • Paper being torn

  3. Question 3

    Which statement about quarks and electrons is correct?

    • Quarks orbit outside the atom like electrons.
    • Electrons are made of three quarks.
    • Quarks and electrons are both made of protons.
    • Quarks build protons and neutrons, and electrons are a different kind of particle called leptons.

  4. Question 4

    Which particle has a negative charge?

    • neutron
    • proton
    • nucleus
    • electron

  5. Question 5

    A compound is…

    • a gas
    • a mix of two liquids
    • two or more elements chemically joined
    • any metal

  6. Question 6

    What is a pure substance made of only one kind of atom called?

    • a compound
    • a mixture
    • an element
    • a solution

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