IGCSE Chem Section 1 - States of Matter

Describe Solids

• strong forces of attraction between particles → close together in fixed positions (LATTICE ARRANGEMENT)

• particles don’t move from position ∴ keep definite shape + volume

• particles vibrate → hotter solids → more vibrate (∴ expand slightly when heated)

Describe liquids

• weak force of attraction between particles ∴ randomly arranged + free to move past each other; tend to stick

• definite volume but not definite shape → flow to fill bottom of container

• particles constantly moving w random motion → hotter liquid gets → faster movement ∴ expands slightly when heated

Describe gases

• very weak forces of attraction ∴ free to move, far apart (most kinetic energy)

• travel in straight lines

• don’t keep definite shape/volume → always fill container

• particles move constantly + random motion → hotter solid gets → faster movement. Either expand when heated or ↑ pressure

Describe melting

• when a solid is heated, its particles gain more energy (kinetic)

• makes the particles vibrate more and weakens the forces that hold the solid together → expands

• at a certain temperature, particles have enough energy to break free from position

Describe evaporating

• When a liquid is heated, the particles gain more energy

• makes particles move faster → weakens + breaks the bond holding liquid together

• at a certain temperature, the particles have enough energy to break their bonds

Define diffusion

• movement of particles through a liquid or gas

• gradual movement of particles from place w lots to place w less

• natural tendency for stuff to spread out

Describe potassium maganate (VII) and water experiment to show diffusion and dilution

• take beaker of water + potassium manganate (VII) to bottom → purple colour slowly spreads

  • random motion in liquid making it evenly spread out

• if you were to add more water to final purple solution → spread even further apart → less purple → dilution

what is a solution

mixture of a solute + solvent that does not seperate

what is a solute

substance being dissolved

what is a solvent

liquid it’s dissolving into

what is a saturated solution

solution where the max amount of solute has been dissolved ∴ no more solute will dissolve in the solution