This document covers all the content for Year 9 Chemistry October Assessment and covers the basics of the GCSE Chemistry Course from Atom Theory to Elements and Compounds
The particle theory is where we use tiny circles to indicate molecules in different states of
matter.
In a solid, the particles have strong bonds and a regular shape. Particles in the solid only vibrate,
they cannot move.
In a liquid, the particles have weak bonds and a quite random structure. Particles in the liquid
can move slowly and have to be connected to at least one other particle.
In a gas, particles can move around freely and don’t take any shape. Particles in a gas can move
around randomly and very fast.
Atoms, elements and compounds
Atom: the smallest unit in existence
Elements: Elements are only made out of 1 singular type of atom
Compound: Where two more different elements are chemically bonded together
Mixture: Where two or more different substances aren't chemically bonded
Molecules: Where two or more atoms are chemically bonded.
Chemical Formulae
Chemical formulae are the way you present out a substance using the Periodic Table.
An example of this is a substance with two hydrogen atoms and one oxygen atom.
First of all, we need to correlate the names of the elements to its chemical symbol: Hydrogen ->
H, Oxygen ->O
Second of all you need to find out how many atoms of each are needed e.g. hydrogen has 2
atoms, oxygen has 1 atom
If we have two hydrogen atoms, we take the chemical symbol then write a 2 next to it e.g. H2.
And then we add a O at the end to represent the 1 oxygen atom
So, two hydrogen atoms and one oxygen atom are H 2O.
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