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GCSE AQA Chemistry Paper 1 Cheat Sheet (DRAFT) by

Notes from https://www.youtube.com/watch?v=pPezIZ8AblM

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Chemical Reactions

Element
a substance containing only one type of atom eg Mg, O2
Compound
a substance containing two or more different types of atoms that are CHEMICALLY BONDED
Equations must be balanced due to the PRINCIPLE OF CONSER­VATION OF MASS

Mixtures & Separation Techniques

Filtration
removes large, insoluble particles from a liquid. eg, sand from water
Evapor­ation
leaves behind crystals of a dissolved substance (solute) if heated gently (CRYSTA­LLI­SATION)
Distil­lation
involves condensin the evaported solvent and collecting it
Fractional Distil­lation
can separate liquids due to their different boiling points
Chroma­tog­raphy
causes substance to rise up due to CAPILLARY ACTION. Lighter particles move further up (links to paper 2)

States of Matter

Solid
- particles in regular arrang­ement (lattice)
- vibrate about FIXED POSITIONS
- cannot be compressed
Liquids
- particles have no regular arrang­ement
- able to move past each other
- cannot be compressed
Gas
- particles are far apart
- move randomly at fast speeds (high energy)
- can be compressed
Solid --> Liquid
melting
Liquid --> Gas
evapor­ation or boiling
Gas --> Liquid
condensing
Liquid --> Solid
freezing or solidi­fic­ation
Solid <--> Gas
sublim­ation
Physical Change
no new substance made
Energy (heat) is needed to overcome the ELECTR­OSTATIC FORCES OF ATTRACTION between particles to melt/e­vap­orate substances

Atomic Structure

Ancient Greeks
thought that matter was made of small indivi­sible particles
JJ Thomson
- plum pudding model
- a ball of an overall positive charge
- small, negatively charged electrons embedded throughout
Ernest Rutherford
- discovered that the nucleus was small and positively charged
- gold leaf alpha scattering experiment
- most particles went straight through but some were deflected back
- cloud of electrons surrou­nding nucleus
Neils Bohr
- electrons exist in "­she­lls­"
James Chadwick
- nucleus must contain protons and neutrons
------­---­---­---­---­---­---­---­---­---­---­---­---­---­---­---­---­---­---­------
Subatomic Particle
Relative Charge
Relative Mass
proton
+1
1
neutron
0
1
electron
-1
0 (very small)

Atomic & Mass Numbers

Mass Number (Ar)
- top number
- number of protons + neutrons in a nucleus
Atomic Number
- bottom number
- number of protons in a nucleus
- an atom must also have this number of electrons in order to be neutral. If not, it is an ion instead.
Some mass numbers are not whole numbers because the Ar is an AVERAGE of all isotopes
average mass = total mass of 100 atoms/100

Develo­pment of the Periodic Table

The elements were initially ordered according to their ATOMIC "­WEI­GHT­" even though grouped together due to having SIMILAR PROPERTIES
DMITRI MENDELEEV realised that it made more sense to swap/r­everse the order of some elements
His table had gaps in, which he predicted would be for elements not yet discovered
In time, this table was proven largely correct due to PEER REVIEW and so it is not the basis of the modern periodic table

Metals & Non-Metals

Metals
- left of the periodic table
- always DONATE electrons to gain an empty outer shell
- they form POSITIVE IONS
- transition metals also form positive ions but form different numbers
Non-Metals
- right of the periodic table
- always ACCEPT electrons to gain a full outer shell
- can share electrons (see bonding)

Groups 1, 7 and 0

Group 1 - Alkali Metals
- react with water to produce an alkali
- they all form a 1+ ion (eg Na+)
- Get MORE REACTIVE as you go down the group because the outer shell electron is further from the nucleus so is donated more readily due to the lower force of attraction so easier to lose an electron
Group 7 - Halogens
- form 1- ion (eg Cl-)
- boiling point increases going down the group
- they get LESS REACTIVE going down the group as the force of attraction decreases so harder to gain an electron
Group 0 - Noble Gases
- very unreactive as they already have an empty outer shell
The final bullet point for Group 1 and 7 is a very common 3-5 mark question so learn it in detail! 3 marks is common for either group and 5 marks is usually for both together.

Groups 1, 7 and 0

Group 1 - Alkali Metals
- react with water to produce an alkali
- they all form a 1+ ion (eg Na+)
- Get MORE REACTIVE as you go down the group because the outer shell electron is further from the nucleus so is donated more readily due to the lower force of attraction so easier to lose an electron
Group 7 - Halogens
- form 1- ion (eg Cl-)
- boiling point increases going down the group
- they get LESS REACTIVE going down the group as the force of attraction decreases so harder to gain an electron
Group 0 - Noble Gases
- very unreactive as they already have an empty outer shell
Transition Metals
- can donate different numbers of electrons
- Iron (II) => Fe2+ while Iron (III) => Fe3+
The final bullet point for Group 1 and 7 is a very common 3-5 mark question so learn it in detail! 3 marks is common for either group and 5 marks is usually for both together.