States of Matter: Particle Model
50 lessons, pages 121–170.
- The Three States of Matter — Solids, liquids and gases in everyday life
- Everything Is Made of Particles — The central idea of the particle model
- Particles in a Solid — Close-packed, regular and vibrating in place
- Particles in a Liquid — Close together but free to slide past each other
- Particles in a Gas — Far apart, fast and randomly moving
- Comparing Solids, Liquids and Gases — Arrangement, spacing and motion side by side
- Drawing Particle Diagrams — Representing the three states correctly
- Forces Between Particles — Attractions that hold particles together
- Particle Energy and Temperature — Faster particles mean a higher temperature
- Why Solids Keep Their Shape — Fixed positions and strong attractions
- Why Liquids Flow and Take the Shape of Their Container — Particles that move around one another
- Why Gases Fill Any Container — Particles that spread out in every direction
- Compressing Solids, Liquids and Gases — Why only gases squash easily
- Gas Pressure and Particle Collisions — Particles hitting the walls of a container
- Heating a Gas in a Closed Container — Temperature, collisions and pressure
- Expansion When Heated — Particles vibrate or move more and take up more room
- Brownian Motion: Evidence for Moving Particles — Random jiggling of pollen and smoke grains
- What Is Diffusion? — Net movement from high to low concentration
- Diffusion in Gases — How smells spread through a room
- Diffusion in Liquids — Colour spreading through still water
- Why Diffusion Is Slow in Liquids and Absent in Solids — Crowded particles and frequent collisions
- Temperature and the Rate of Diffusion — Faster particles spread more quickly
- Particle Mass and the Rate of Diffusion — Lighter particles move faster at the same temperature
- The Ammonia and Hydrogen Chloride Tube Demonstration — Where the white ring forms and why
- Diffusion in Living Things and Everyday Life — Breathing, cooking and air fresheners
- Changes of State: An Overview — Melting, freezing, boiling, condensing and subliming
- Changes of State Are Physical Changes — Same substance, different arrangement
- Melting — Particles breaking free from fixed positions
- Melting Point — The fixed temperature at which a pure solid melts
- Freezing and Solidifying — Particles settling back into fixed positions
- Boiling — Bubbles of gas forming throughout a liquid
- Boiling Point — The fixed temperature at which a pure liquid boils
- Boiling Point and Air Pressure — Why water boils below 100 °C on a mountain
- Condensation — Gas particles slowing and clumping into liquid
- Sublimation and Deposition — Changing directly between solid and gas
- Energy Transfer During Changes of State — Taking in or giving out energy
- Heating Curves — Temperature against time as a solid is heated
- Why Temperature Stays Constant While Melting and Boiling — Energy used to overcome attractions
- Cooling Curves — Temperature plateaus during freezing and condensing
- Predicting State from Melting and Boiling Points — Solid, liquid or gas at a given temperature
- Melting and Boiling Points as a Test of Purity — Sharp values for pure substances, ranges for mixtures
- Strength of Attractions and Melting and Boiling Points — Stronger forces need more energy to overcome
- What Is Evaporation? — Fast particles escaping from a liquid surface
- Evaporation Compared with Boiling — Surface only at any temperature versus throughout at one temperature
- Factors Affecting the Rate of Evaporation — Temperature, surface area, air flow and humidity
- Evaporation Causes Cooling — Why sweating cools the body
- Volatile Liquids — Liquids that evaporate easily and their hazards
- States of Matter in the Water Cycle — Evaporation, condensation and freezing in nature
- Limits of the Simple Particle Model — What the hard-sphere picture leaves out
- States of Matter: Unit Review — Connecting particles, diffusion, changes of state and evaporation