1bPrinciples of Chemistry
Elements, compounds and mixtures — Edexcel Modular - OL (Chemistry) Revision Notes & Topical Questions
5 min read 7 parts Lesson 2 of 9 2 quizzes
Lesson summary
Elements, compounds and mixtures Edexcel O Level Modular Chemistry notes: understand how to classify a substance as an element, compound or mixtureAn element contains only one type of atom.A compound has properties different from the elements that made it.The elements in a compou…
- Elements, compounds and mixtures Edexcel O Level Modular Chemistry: what to do next
- Filtration
- Distillation
- Separation
- Evaporation
- Give / State / Name
Section 1 of 7Process & sequence
Getting pure salt from rock salt
1
Crush the rock salt.
2
Stir it into warm water so the salt dissolves.
3
Filter: the sand stays on the filter paper, the salt solution passes through.
4
Heat the salt solution in an evaporating basin.
5
Salt crystals are left behind as the water evaporates.
- Rock salt
- dissolve
- filter
- evaporate
- Pure salt
Section 2 of 7Keep going
Elements, compounds and mixtures Edexcel O Level Modular Chemistry: what to do next
These Elements, compounds and mixtures Edexcel O Level Modular Chemistry notes covered the key ideas, worked examples and exam technique for this topic. Check your Elements, compounds and mixtures Edexcel O Level Modular Chemistry understanding with the practice questions below, then reread any Elements, compounds and mixtures Edexcel O Level Modular Chemistry point you were unsure about before moving on.
2
Previous lesson: 1a States of matter — Notes
3
Next lesson: 1c Atomic structure — Notes
5
Official syllabus: Pearson Edexcel International GCSEs
Section 3 of 7Compare
| Feature | Element | Compound | Mixture | How to tell them apart | Example |
|---|---|---|---|---|---|
| Made of | One type of atom | Two or more elements | Two or more substances | Count the kinds of atom | Iron; water; air |
| Chemically joined? | - | Yes | No | A compound needs a reaction to form | Iron + sulfur heated gives iron sulfide |
| Fixed proportions? | - | Yes, always | No, any amounts | Water is always H2O | Salty water can be weak or strong |
| Properties | Its own | Different from its elements | Each part keeps its own | Sodium chloride is not like sodium or chlorine | Iron filings in sand stay magnetic |
| Separated by | Cannot be split | A chemical reaction only | Physical methods | Filtering, distilling, a magnet | Sand from water by filtering |
Section 4 of 7Key terms
Section 5 of 7Syllabus checklist
1
understand how to classify a substance as an element, compound or mixture
2
understand that a pure substance has a fixed melting and boiling point, but that a mixture may melt or boil over a range of temperatures
3
describe these experimental techniques for the separation of mixtures: - simple distillation - fractional distillation - filtration - crystallisation - paper chromatography.
4
understand how a chromatogram provides information about the composition of a mixture
5
understand how to use the calculation of Rf values to identify the components of a mixture
6
practical: investigate paper chromatography using inks/food colourings
Section 6 of 7Command terms
Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.
Section 7 of 7Exam technique
Keywords the mark scheme looks for in this lesson
Keywords the mark scheme looks for in this lesson
Element · Compound · Mixture · Formula · Filtration · Distillation · Separation · Evaporation
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.
How to get full marks (examiner guidance)
How to get full marks (examiner guidance)
Use specification keywords exactly (e.g. electronegativity, nucleophile, dynamic equilibrium, activation energy).
Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
Convert units carefully (mg → g, cm³ → dm³) and show working for calculations.
Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
Do not extrapolate a graph line beyond the data or to zero unless asked.
Six-mark extended responses are marked on content AND a logical, linked line of reasoning.
Marked practiceQuizzes for this lesson
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