GCSE AQA Extension Science Chemistry Revision Notes


 Chemistry Revision

·         Tests for Cations (+)

o   Flame colour for identification= Sodium (Na)- Potassium (K)- Calcium (Ca2)- Copper(CU2)- lithium (Li)

o   Some metals form a coloured precipitate with NaOH


§  Cu2

§  Fe2

§  Fe3

§  Al3- white to colourless


o   Ammonium + NaOH= Ammonia

§  Ammonia stinks and turns damp red litmus paper, blue.

·         Tests for Anions (-)

o   Testing for Carbonates

§  Acid + Carbonate= Salt+ water+CO2

§  CO2 turns limewater cloudy

§  Also you can put 1 spatula of carbonate and heat strongly. Copper Carbonate goes green to black and stays black. Zinc Carbonate goes from white to yellow and back to white.

o   Testing for Sulfates

§  Add dilute hydrochloric acid followed by barium chloride solution

§  It goes white if compound was a sulphate

o   Testing for halides

§  Add dillute Nitric acid followed by silver nitrate solution

§  Chloride

§  Bromide

§  Iodide

o   Testing for nitrates

§  Add aluminium powder and sodium hydroxide and heat.

§  You’ll get ammonia ( tests for ammonia shown above)

·         Tests for Organic Compounds

o   Organic chemicals contain carbon and it’s compounds

o   Carbon’s presence causes them to burn when heated with a yellow orange or blue flame

o   Unsaturated organic moles contain C=C double bonds… they decolourise bromine water

·         Empirical Formulae & Combustion Analysis

o   The empirical formula is the simplest ratio of atoms in a molecule or compound

o   Combustion Analysis finds the empirical formula of a compound:

§  Compound’s mass is measured

§  It is burned in excess oxygen

§  CO2 and water produced is measured

§  Mass of Carbon x proportion of C in CO2 (12/44= 0.2727)

§  Mass of Hydrogen  x proportion of H in H2O (2/18= 0.111)

§  Divide theses masses by the atomic number of C and H (to find number of moles)

§  Divide by smallest to get simplest ratio.

·         Instrumental Analysis

o   Atomic Spectrometers- Analyse energy (usually light) using a line emission spectrum. Patterns are then matched to existing frequencies on a database

o   Infrared Spectroscopy- detects specific bonds in organic chemicals

o   Ultraviolet Spectroscopy- analyses levels of nitrates + phosphates in water

o   Nuclear magnetic resonance spectroscopy- used to detect some organic molecules

o   Gas-liquid chromatography- separates gases through a column- identified by the distance moved

o   Mass spectrometer- used for elements + ions. Masses of fragments used to identify what is in a sample.

·         Acids- Hydrogen (H+ )ions and proton donors

·         Alkalines-Hydroxide (OH– )ions and protons acceptors

·         Strong acid/alkali= completely ionised

·         Weak acid/alkali=Partially ionised

·         Titrations

o   Measure out 25cm3


ashlea osborne


Calcium should be brick red and lithium bright red.

metals reacted with NaOH: Ca2 goes colourless, Cu2 goes blue,Fe2 goes a slugdy green, Fe3 goes orangey brown (like rust) Al3 goes from white to colourless and Mg2 goes colourless.

Some of my colours haven't shown up so if i've misssed any please let me know. These are the revision notes I have done for my chemistry exam on wednesday. If these helped you in your revision, I am glad and Thank You for using this resources.