IGCSE Combined Science - States of Matter

C1 States of Matter

C1.1 Solids, Liquids, and Gases

Core Objectives
  • Distinguishing Properties: State the properties that differentiate solids, liquids, and gases.
  • Structure Description: Describe the structures of solids, liquids, and gases regarding particle separation, arrangement, and motion.
  • Changes of State: Describe changes of state, including melting, boiling, evaporating, freezing, and condensing.
Supplement Objectives
  • Kinetic Particle Theory: Explain changes of state using the kinetic particle theory.
  • Temperature and Pressure: Describe the effects of temperature and pressure on the volume of a gas.

Kinetic Theory & Different States

  • Kinetic Theory: Explains differences between states of matter.
  • Solid
    • Particles have low kinetic energy (KE).
    • Particles are held together by intermolecular forces of attraction.
  • Liquid
    • Particles have more kinetic energy to stretch intermolecular forces.
  • Gas
    • Particles have enough kinetic energy to break all intermolecular forces of attraction.

Kinetic Energy of Particles of Matter

PropertySolidLiquidGas
Kinetic EnergyLow KE levelsHigher KE levelsHigh KE levels
Shape/VolumeRetains own shapeTakes shape of containerTakes shape of container
CompressibilityHighly incompressibleSlightly compressibleHighly compressible
Molecular MotionSlow-moving moleculesFaster moving moleculesVery fast-moving molecules
Molecular BondsVery strong molecular bondsWeak intermolecular bondsNo intermolecular bonds
Intermolecular SpacingSmall intermolecular spacingLarger intermolecular spacingVery large intermolecular spacing

Changes in States of Matter

  • Phase Transitions
    • Sublimation: Solid to Gas
    • Melting: Solid to Liquid
    • Evaporation: Liquid to Gas
    • Freezing: Liquid to Solid
    • Condensation: Gas to Liquid
    • Deposition: Gas to Solid

Boiling vs. Evaporation

FeatureBoilingEvaporation
TemperatureOccurs at a fixed temperatureOccurs at any temperature
SpeedRelatively fast processRelatively slow process
LocationThroughout the liquidAt the surface only
Bubble FormationBubbles are formedNo bubbles
Temperature ChangeTemperature remains constantTemperature may change
Energy SourceExternal thermal energyHeat from surroundings

Cooling Curve

  • Temperature Decrease: As temperature falls, particle energy decreases.
  • Slower Movement: Particles move more slowly and interact more strongly.
  • Liquid Formation: Particles come together as a liquid.
  • Energy Release: Intermolecular forces increase, releasing energy.
  • Constant Temperature: Temperature remains constant during condensation until complete.
  • Intermolecular Forces: Weak attractive forces between molecules.
  • Melting: When a solid is heated, the temperature rises until melting starts, then remains constant until all solid melts.

Effect of Temperature and Pressure on the Volume of a Gas

  • Pressure
    • Increase in external pressure →\rightarrow decrease in volume (compression).
    • Decrease in external pressure →\rightarrow increase in volume (expansion).
  • Temperature
    • Increase in temperature →\rightarrow increase in volume (expansion).
    • Decrease in temperature →\rightarrow decrease in volume (compression).

Coursebook Exercises

  • Page 256: C1.01, C1.02, and C1.03
  • Page 257: C1.04
  • Page 261: C1.06
  • Practice Questions (pages 267 – 269)
    • Page 267: Q1
    • Page 268: Q2
    • Page 269: Q4