Diffusion

• all matter made of up particles, this proves it

• spontaneous mixing/spreading of one substance into another from region of high concentration to region to low concentration, until particles evenly spread

• result of brownian motion

  • constant, rapid and irregular motion of particles

States of Matter

depends on

• kinetic energy between particles

• intermolecular forces

• temp is a measure of the average kinetic energy of particles

  • kinetic energy increased, can overcome intermolecular forces

    → phase change

heating and cooling curves

• changes in temperature in phase changes

  → temp stays constant until phase is changed

  • this is because all the heat energy used overcoming intermolecular forces

    • latent heat

Kinetic Molecular Theory

• describes movement of particles in matter

  • allows us to explain what we observe

basic assumptions

• matter made up tiny particles (atoms, ions and molecules)

• constant, random motion

• higher temp = faster speed

  energy and movement of particles

• solid have low energy particles that vibrate

• liquids have more energy that slide over one another

  • gas high energy → constantly moving

Particles making up Substances

compound → two or more elements chemically combined in a fixed ratio

atom → smallest building block of matter

• substances form from the combining of atoms

  • ionic bonding

  • metallic bonding

  • molecular substances

    →covalent molecular structures

    →covalent network structures

covalent (or simple) molecular structures

• relatively small molecules interacting as seperate molecules

  can be elements → oxygen - O2, sulphur - S8, buckminsterfullerene - C60

  compounds → water - H2O, octane - C8H18

properties

• forces individual molecules weaker therefore not very strong physically

• low MP and BP

• poor conductors as no free electrons/ions to carry charge

• most small molecules will dissolve in some solvent → solution

covalent network structures

• giant 3d lattices → held single covalent bonds

  • Carbon as diamond

  • Carbon as graphite

    • (allotropes - forms of same element with differing properties)

  • Silicon dioxide as silica

properties

• high MB and BP

• poor conductors → electrons not free to move

• very hard, not soluble in water bc strength of bonding in all directions of structure

  Graphite

  • bonding leaves mobile electrons → can conduct

  • layers held weak bonds therefore used as engineering lubricant

ionic structures

• alternate postive/negative ions arranged in orderly way in giant ionic lattice

• ionic bond is the strong attraction between pos/neg in lattice

• bonding extends throughout the crystal all directions

properties

• high BP - strong attractions to be broken

• conductors when molten/in a solution (ions carry electric charge when free to move)

• hard and brittle

• mostly soluble - charged ions can be carried off by polar molecules

metallic structures

• ions surrounded by sea of electrons → another type of giant lattice

• outer electrons free to move between positive metal ions

  → electronic glue

properties

• dense, strong, high MP/BP

• free electron carry charge → good conductors

• conduct heat

• malleable

  → bonds not in a fixed direction so don’t fracture

Representing Molecules

formula

• molecular formula - exact

• empirical formula - simplified

• structural formula - used describe compound

diagrams

• wireframe / stick models

  • sticks

• ball and stick models

  • balls and sticks

• space-filling model

  • spheres