People have kept asking for a guide on the practicals. As I have explained before I am not producing one. It is worth remembering paper 3 is only partially practical based. There will be multiple choice questions and short answer questions on all parts of the syllabus. There are no short cuts. You need to know everything practical or non practical. It is not going to be an easy paper.
You will need to know the 12 required practicals but you will also get questions on other practicals which may be unfamiliar.
Practical questions could be about:
- write the method for a common practical
- draw diagrams of common apparatus
- create a method for an unusual experiment
- suggest improvements to a given method
- state why a step in a method is done
- draw graphs, take gradients and make conclusions from given results
- see if results confirm a given hypothesis
- give expected observations for a reaction
- write chemical equations that match observations given
- describing causes of common errors
- explain how errors could be minimised
- explain what effect errors might have on the result
The 12 required practicals for AQA are given below with the relevant revision guides where I have mentioned them. For some I have included brief methods where I think they are needed but not all. You should refer to your practical work for the full methods or the AQA practical handbook.
1 Make up a volumetric solution and carry out a simple acid–base titration – s1.2 revision guide calculations and see 1.25 titrations for lots of questions on errors and method
2 Measurement of an enthalpy change see 1.4 revision guide energetics
Consider – neutralisation reactions, solution plus solid and combustion reactions
3 Investigation of how the rate of a reaction changes with temperature see 1.5 Kinetics
Usually sodium thiosulphate and acid –the result from this experiment can be used to work out activation energy see 1.9 Rate Equations
4 Carry out simple test-tube reactions to identify:
- cations – Group 2, NH4+ see 2.2 Group 2
- anions – Group 7 (halide ions), OH–, CO3 2–, SO42– see 2.2 Group 2 and 2.3 Halogens
5 Distillation of a product from a reaction see3.5 revision guide alcoholss and 3.14 Synthetic routes
6 Tests for alcohol, aldehyde, alkene and carboxylic acid see 3.6 Analysis and 3.14 revision guide organic synthesis
7 Measuring the rate of reaction: see 1.9 Rate Equations or 4. Reaction Kinetics
- by an initial rate method – generally ‘clock reactions’ or timing how long it takes for a cross to disappear
- by a continuous monitoring method- generally following with a gas syringe, but could be titration of samples or colorimeter
8 Measuring the EMF of an electrochemical cell see 1.11 Redox Equilibria
9 Investigate how pH changes when a weak acid reacts with a strong base and when a strong acid reacts with a weak base see 1.12 revision guide acid base equilibria
10 Preparation of:
- a pure organic solid and test of its purity see 3.9 revision guide carboxylic acids and derivativesand 3.14 revision guide organic synthesis
- a pure organic liquid see 3.14 revision guide organic synthesis for purification steps
11 Carry out simple test-tube reactions to identify transition metal ions in aqueous solution see 2.5 Transition Metals and 2.6. Reactions of Inorganic Compounds in Aqueous Solution
12 Separation of species by thin-layer chromatography see 3.16 Chromatography and 3.13 revision guide amino acids proteins and DNA
Other important experiments commonly asked about in the past that could still well come up:
Simple measuring mass and gas volume experiments such a heating a hydrated salt or measuring the Mr of a volatile liquid see 1.2 revision guide calculations
Colorimeters see 2.5 Transition Metals
Redox titrations and EDTA titrations see 2.5 Transition Metals
Autocatalysis reaction see 2.5 Transition Metals
Measuring an equilibrium constant for an esterification reaction 1.6 revision guide equilibria
Comparing rates of hydrolysis of halogenoalkanes see 3.3 Halogenoalkanes
Any test tube reaction from inorganic or organic part of syllabus
Don’t forget
Calculating uncertainties and safety see 1.2 Calculations