Particulate Nature of Matter

Properties of solid, liquid, and gases

Fixed volumeFixed volumeNo definite volume
Fixed shapeNo definite shapeNo definite shape
Cannot be compressedOnly compressed a littleCan be compressed
Particles close togetherParticles close togetherParticles far apart
Particles arranged in regular patternParticles arranged randomlyParticles arranged randomly
Particles vibrate around a fixed pointParticles slide over each other randomlyParticles move randomly and rapidly

Changes of state

Solid to liquid: melting
Liquid to gases: evaporation
Liquid to solid: freezing
Gas to liquid: condensing

Solid to gas: sublimation
Gas to solid: sublimation

Note: sublimation is often asked in mcq questions

There is no temperature change while a change of state is occurring

Kinetic Particle theory

Kinetic theory: Particles behave as hard spheres, constantly moving from place to place (in liquids and gases) and vibrate upon a fixed position (in solids)

• In gases, particles are constantly colliding and changing directions resulting in random movement.
• As temperature increases, particles gain kinetic energy and move faster
• Gases can be compressed easily. Pressure and volume are inversely proportional. This means an increase in pressure at constant temperature results in a decrease in volume.
• Liquids and solids cannot be compressed easily as particles are close together and kinetic theory assumes particles are hard
• Gas in a closed container increases in pressure when it’s heated because the increased kinetic energy moves faster and collide with the walls of the container with greater force

Explanation of changes of state

• Input of energy is needed to melt and boil a substance
• Energy lessens the force of energy when a substance freezes or condenses
• Energy given out when substance freezes or condenses
• During freezing or condensation particles move slower, losing kinetic energy

Heating and Cooling Curves

Brownian motion: the random movement of particles in fluids. This happens because they are bombarded by other moving particles in the fluid.

Examples: Random movement of dust particles in still air

Diffusion: spreading movement of one substance into another due to random motion of the particles.

• Overall movement is from higher concentration to lower concentration
• Diffusion is faster in gases as particles move faster.

During change of state, temperature is constant.

  • Evidence; Pollen grain were being moved by individual water molecules
  • This is how particles are diffused


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