Chemistry - EDEXCEL IGCSE - States of matter, atoms and atomic structure

STATES OF MATTER

ATOMS

Evidence:

1. Dilution of coloured (e.g. copper sulphate solution)

• Use serial dilution (step-wise)
• Each stage shows the same colour but a lighter shade
• Provides evidence of small ‘particles’ which spread out

     2. Diffusion of potassium manganate and water

• Water becomes a purple colour
• Shows evidence of particles which move.

Definitions:

Atom – the basic unit of chemistry and matter it is made of electrons, protons, neutrons.

Molecule – where atoms join together covalently.

Element – a substance made of only one type of atom.

Compound – a substance made up of 2 or more types of atoms chemically bonded and in a fixed ratio.

Mixture – a group of substances not chemically bonded together and not in a fixed ratio.

Atomic number - number of protons

Mass number - number of protons and neutrons in the nucleus

Isotopes - atoms of an element with differing mass numbers but the same atomic number.

Relative Atomic Mass - the weighted average relative to a Carbon - 12 atom.

Formula fo relative atomic mass (Ar):

Ar = ((x * %x) + (y * %y)) / 100

Where x, y = mass of the isotope 

And %x, %y = abundance of the isotope 

ATOMIC STRUCTURE