Chemical Analysis | AQA GCSE Combined Science Trilogy Chemistry, Higher tier (8464)

Chemical Analysis

51 questions
4 subtopics
Chemistry Paper 2
Chemistry Paper 2

Chemical Analysis is examined in Chemistry Paper 2.

It covers pure substances, formulations, chromatography and tests for hydrogen, oxygen, carbon dioxide and chlorine.

Sample questions from Chemical Analysis

Answer each one closed book first, then open the answer.

Pure substances

What is the difference between the way a pure compound changes state and the way a mixture does?

Show the answer
A pure compound melts and boils at specific fixed temperatures, while a mixture melts and boils over a range of temperatures.
Pure substances

What does the word pure usually mean in everyday speech?

Show the answer
It means the substance has had nothing added to it, so it is unadulterated and in its natural state.
Formulations

Name three household products that are formulations.

Show the answer
Paints, medicines and cleaning agents are all formulations.
Formulations

A label lists five ingredients together with the percentage of each. What does this suggest about the product?

Show the answer
It is a formulation, because it is a mixture whose components are present in carefully measured proportions.
Chromatography

A spot moves 3.6 cm from the origin while the solvent moves 8.0 cm. Calculate its Rf value.

Show the answer
Rf is 3.6 ÷ 8.0, which is 0.45.
Chromatography

How does a chromatogram show that a sample of dye is impure?

Show the answer
The sample separates into more than one spot, so it must contain more than one substance.
Tests for hydrogen, oxygen, carbon dioxide and chlorine

A glowing splint bursts back into flame when it is pushed into a test tube of gas. Which gas is present?

Show the answer
It is oxygen.
Tests for hydrogen, oxygen, carbon dioxide and chlorine

A gas is bubbled through limewater and the limewater stays clear. What can you conclude?

Show the answer
The gas is not carbon dioxide, because carbon dioxide would turn the limewater milky.

The 4 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Pure substances	The chemical meaning of a pure substance, why pure substances melt and boil at fixed temperatures while mixtures change state over a range, using melting and boiling points to test purity, and the everyday meaning of pure compared with the chemist's.	12
Formulations	What a formulation is and why its components are measured in controlled quantities, the purpose of each ingredient, examples such as paints, medicines, cleaning agents, fertilisers, fuels, alloys and food sauces, and telling a formulation from a single compound or a natural mixture.	11
Chromatography	The stationary and mobile phases, what decides how far a substance travels, how Rf values are defined and calculated, reading purity from a chromatogram, and why the start line is pencil and the solvent starts below it.	16
Tests for hydrogen, oxygen, carbon dioxide and chlorine	The burning splint test for hydrogen, the glowing splint test for oxygen, limewater turning milky for carbon dioxide, damp litmus paper bleached white by chlorine, why each test is carried out as it is, and identifying a gas from the result.	12

Chemical Analysis is 51 of the 1,222 questions in the guide.Get the guide, £7

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.