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Acids, alkalis and titrations — Edexcel Modular - OL (Chemistry) Revision Notes & Topical Questions

5 min read 7 parts Lesson 6 of 8 2 quizzes

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Lesson summary

Acids, alkalis and titrations Edexcel O Level Modular Chemistry notes: describe the use of litmus, phenolphthalein and methyl orange to distinguish between acidic and alkaline solutions understand how to use the pH scale, from 0-14, can be used to classify solutions as strongly a…

  • Acids, alkalis and titrations Edexcel O Level Modular Chemistry: what to do next
  • Hazard symbol
  • Give / State / Name
  • Evaluate / Assess
  • Keywords the mark scheme looks for in this lesson
  • How to get full marks (examiner guidance)

Section 1 of 7Process & sequence

  • pH 0 strong acid
  • weak acid
  • pH 7 neutral
  • weak alkali
  • pH 14 strong alkali
Safety
Wear goggles
Never taste chemicals
Wash spills with plenty of water
Read hazard symbols

Section 2 of 7Keep going

Acids, alkalis and titrations Edexcel O Level Modular Chemistry: what to do next

These Acids, alkalis and titrations Edexcel O Level Modular Chemistry notes covered the key ideas, worked examples and exam technique for this topic. Check your Acids, alkalis and titrations Edexcel O Level Modular Chemistry understanding with the practice questions below, then reread any Acids, alkalis and titrations Edexcel O Level Modular Chemistry point you were unsure about before moving on.

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Practice: Acids, alkalis and titrations Edexcel O Level Modular Chemistry practice questions
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Previous lesson: 2.2 Extraction & uses of metals — Notes
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Next lesson: 2g Acids, bases and salt preparations — Notes
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Course: Edexcel Modular – OL (chemistry) — all units
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Official syllabus: Pearson Edexcel International GCSEs

Acids, alkalis and titrations Edexcel O Level Modular Chemistry revision notes

Section 3 of 7Compare

Acids, alkalis and neutral substances
TypepHTaste / feelEveryday examplesLab examplesLitmus colour
Strong acid0–3Corrosive—Hydrochloric, sulfuric acidRed
Weak acid4–6SourLemon juice, vinegarEthanoic acidRed
Neutral7—Pure water, salt solutionDistilled waterNo change (purple)
Weak alkali8–10SoapyToothpaste, soap—Blue
Strong alkali11–14Corrosive, slipperyOven cleaner, bleachSodium hydroxideBlue

Section 4 of 7Key terms

Section 5 of 7Syllabus checklist

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describe the use of litmus, phenolphthalein and methyl orange to distinguish between acidic and alkaline solutions understand how to use the pH scale,
  • from 0-14, can be used to classify solutions as strongly acidic (0-3), weakly acidic (4-6), neutral (7), weakly alkaline (8-10) and strongly alkaline (11-14)
2
describe the use of universal indicator to measure the approximate pH value of an aqueous solution
3
know that acids in aqueous solution are a source of hydrogen ions and alkalis in a aqueous solution are a source of hydroxide ions
4
know that alkalis can neutralise acids

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
Acid · Alkali · Neutral · Corrosive · Hazard symbol · pH scale · Indicator · Base
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.

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