1. Which state is readily compressed?
- Solid
- Gas
- Liquid
Check the answer and reasoning
Gas
Gas particles have large separations compared with their sizes.
CHEM / Foundations
Particles, states and changes
Matter is described using particles: solids retain closely arranged particles, liquids flow and gases spread through the available space. Particle diagrams are models, not pictures at true scale.
Learning objectives
- Explain particles, states and changes using a concrete example.
- Apply the worked method and justify each step.
- Recognise the limitation described in the final check.
The big idea
Matter is described using particles: solids retain closely arranged particles, liquids flow and gases spread through the available space. Particle diagrams are models, not pictures at true scale.
A change of state rearranges particles without changing their chemical identities. A chemical reaction forms substances with different compositions or structures; temperature change alone is not a sufficient test.
Worked example
Ice melts into water. Is this a physical or chemical change?
Follow the solution
The substance remains H₂O; its particles become less fixed in position.
Investigate and explain
Predict the worked result before calculating. Change one input, record the new result, and explain which assumptions still hold.
Related interactive model. Compare its assumptions with the explanation; it is not a complete syllabus lesson.
Check your understanding
2. Ice melts into water. Is this a physical or chemical change?
- Chemical change
- Nuclear change
- Physical change
Check the answer and reasoning
Physical change
The substance remains H₂O; its particles become less fixed in position.
3. Does boiling water break its molecules into hydrogen and oxygen?
- No
- Yes
- Only at 100°C
Check the answer and reasoning
No
Boiling overcomes intermolecular attractions rather than breaking the covalent bonds within water molecules.