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Science · Grades 6–9

Particle models of matter

A particle model explains observations; it is not a literal photograph of individual particles.

Make a worksheet

Understand the idea

Separate scale levels

A particle model explains observations; it is not a literal photograph of individual particles.

Conservation

In a sealed system, a physical change does not remove matter from the system.

Examples and reasoning

A gas is compressed more easily than a liquid. Which particle-model feature helps explain this?

Gas particles have much more space between them.

Gas particles have much more space between them.

During melting, which statement best describes a simple particle model?

Particles become less fixed in their arrangement.

Particles become less fixed in their arrangement.

Check your understanding

  1. A sealed container holds liquid water and water vapour. When vapour condenses, what happens to total water mass?

    1. It doubles automatically.
    2. It must decrease.
    3. It stays the same if nothing enters or leaves.
    4. It becomes zero.

  2. Which is evidence of diffusion?

    1. A solid gains a name.
    2. A scale is switched off.
    3. A dissolved dye gradually spreads through still water.
    4. A ruler becomes longer on paper.

  3. In a solid, particles are best described as

    1. having no interactions
    2. completely motionless
    3. vibrating around relatively fixed positions
    4. usually kilometres apart

  4. Salt dissolves in water. Which conclusion is justified?

    1. The solution has no mass.
    2. Every atom has changed element.
    3. The salt is dispersed in the solution.
    4. The salt no longer exists.

Answers and marking notes

Answers and marking notes
  1. It stays the same if nothing enters or leaves.

    It stays the same if nothing enters or leaves.

  2. A dissolved dye gradually spreads through still water.

    A dissolved dye gradually spreads through still water.

  3. vibrating around relatively fixed positions

    vibrating around relatively fixed positions

  4. The salt is dispersed in the solution.

    The salt is dispersed in the solution.

Further reading and review references

These are reference links, not copied exercises, institutional endorsement or proof of independent review.

Learning preview · teacher review required. Grade bands are approximate, not official curriculum alignment.