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1.8Chapter 1: The Particle Model and States of Matter

Chapter 1 Review: The Particle Model and States of Matter — Alhussan Chemistry - Stage 7 Revision Notes & Topical Questions

5 min read 8 parts Lesson 8 of 8 2 quizzes

📚 Alhussan Chemistry - Stage 7 Hub / Topical Revision
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Lesson summary

1.8 Chapter 1 Review: The Particle Model and States of Matter — Alhussan International Academy — Chemistry (Stages 7–9) notes: Revise the particle model, changes of state, heating curves and the limits of models from Chapter 1.Solid — the particles touch in a regular pattern and …

  • Properties
  • Physical changes
  • Evaporation
  • Key numbers
  • Puddle drying
  • Steamed-up window

Part 1 of 6States of matter and the particle model

States of matter and the particle model
Solid
  • Solid the particles touch in a regular pattern and only vibrate.
Liquid
  • Liquid the particles touch but are arranged randomly and can slide past each other.
Gas
  • Gas the particles are widely spaced, move rapidly in random directions and have very weak forces between them.
Properties
  • Properties these arrangements explain shape, flow and compressibility.
  • Gases are easily compressed because of the empty space between particles.
  • Solids and liquids are almost incompressible.
Volumes
  • 1 g of liquid water has a volume similar to 1 g of solid water because the particles touch in both states.
  • Melting does not change the separation of the particles.

Part 2 of 6Changes of state

Physical changes
  • Physical changes no new substances are made and the change is reversible.
Mass
  • Mass it is conserved in every change of state.
ChangeFrom and toEnergy
MeltingSolid to liquidIn
FreezingLiquid to solidOut
Boiling or evaporationLiquid to gasIn
CondensationGas to liquidOut
Evaporation
  • Evaporation it takes place slowly at the surface at any temperature, whereas boiling happens throughout the liquid at the boiling point.
Speeding up evaporation
  • Speeding up evaporation higher temperature, greater surface area, moving air and low humidity.
Key numbers
  • Key numbers pure water melts at 0 °C and boils at 100 °C at normal pressure.

Part 3 of 6Explaining everyday events

1Puddle drying
  • Puddle drying evaporation, as the faster surface particles escape from the liquid.
2Steamed-up window
  • Steamed-up window condensation, as water vapour cools and its particles lose energy and come together.
3Ice cube melting in a drink
  • Ice cube melting in a drink melting, with energy taken from the drink so the drink cools.
4Description of a change
  • Description of a change name the change, say whether energy is taken in or given out, and describe particle movement before and after.

Part 4 of 6Heating curves and purity

Rising sections
  • Rising sections particles gain kinetic energy.
Flat sections
  • Flat sections a change of state is taking place, and energy goes into overcoming forces between particles rather than raising the temperature.
Reading the graph
  • Reading the graph the temperatures of the flat sections are the melting and boiling points.
Purity
  • Purity pure substances have sharp melting and boiling points, while mixtures change over a range.

Part 5 of 6Models and their limits

Models and their limits
Particle model
  • Particle model it is a simplification that works well.
Strength
  • Strength it explains states, changes of state and diffusion.
  • Diffusion gives further evidence for the model because it shows that particles must be moving.
Limitations
  • Limitations real particles are not solid spheres, they move constantly, and diagrams cannot show forces or spacing to scale.

Part 6 of 6Precise vocabulary

Precise vocabulary
Particles vibrate, move randomly, attract each other, and overcome forces when a substance changes state.
Particles themselves do not melt or get hot
  • Particles themselves do not melt or get hot they move faster or vibrate more strongly, but the particle is unchanged.

Key terms

TermMeaning
Particle modelA model of matter as tiny moving particles.
EvaporationLiquid changing to gas at the surface at any temperature.
BoilingLiquid changing to gas throughout the liquid at the boiling point.
Heating curveA graph of temperature against time as a substance is heated.
Kinetic energyThe energy of movement of particles.
DiffusionThe spreading of particles from high to low concentration.

Avoid these mistakes

1
Mixing up evaporation and boiling.
2
Thinking particles expand or melt when a solid melts.
3
Drawing a sloping line for a change of state on a heating curve.
4
Saying that gases have no mass.

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