ScienceAges 13-15

Acids, bases & the pH scale

Use the 0–14 pH scale, indicators and neutralisation reactions to classify acidic, neutral and alkaline solutions. Review suitability for your learners before teaching.

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Age band:Ages 13-15 Ages 16-18

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Worksheet StudioPractice pack · Ages 13-15

Acids, bases & the pH scale

Take your time. Show your thinking.

1. What colour does red litmus paper turn when dipped into an alkaline solution: blue or yellow?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
2. Which solution is more strongly acidic: Solution A with pH 1, or Solution B with pH 5?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
3. Which ion is present in all aqueous alkaline solutions: hydroxide ions (OH⁻) or chloride ions (Cl⁻)?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
4. On the standard pH scale (0 to 14) at 25 °C, what is the pH of a neutral solution such as pure water: 7 or 0?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
5. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
6. What is the chemical test that confirms a gas is carbon dioxide (CO₂): it turns clear limewater cloudy (milky), or it relights a glowing splint?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
7. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
8. Which gas is produced when a reactive metal (such as magnesium or zinc) reacts with dilute hydrochloric acid: hydrogen or oxygen?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
9. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
10. Which salt is formed when hydrochloric acid (HCl) is neutralised by sodium hydroxide (NaOH): sodium chloride or sodium sulfate?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
11. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
12. Does an alkaline (basic) solution (such as sodium hydroxide or soapy water) have a pH greater than 7 or less than 7?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

12 questions · Seed 58 · Age guidance, not curriculum certification

View the answer key

Worksheet StudioAnswer key · Ages 13-15

Acids, bases & the pH scale

Answers and reasoning. Review before teaching.

1. What colour does red litmus paper turn when dipped into an alkaline solution: blue or yellow?
Blue
Alkalis turn red litmus paper blue.
2. Which solution is more strongly acidic: Solution A with pH 1, or Solution B with pH 5?
Solution A with pH 1
Lower numbers on the pH scale indicate higher hydrogen-ion concentration and stronger acidity.
3. Which ion is present in all aqueous alkaline solutions: hydroxide ions (OH⁻) or chloride ions (Cl⁻)?
Hydroxide ions (OH⁻)
Alkalis dissolve in water to release hydroxide ions (OH⁻).
4. On the standard pH scale (0 to 14) at 25 °C, what is the pH of a neutral solution such as pure water: 7 or 0?
7
A pH of 7 is neutral, with equal concentrations of H⁺ and OH⁻ ions.
5. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
Red
Acids turn blue litmus paper red.
6. What is the chemical test that confirms a gas is carbon dioxide (CO₂): it turns clear limewater cloudy (milky), or it relights a glowing splint?
It turns clear limewater cloudy (milky)
CO₂ reacts with calcium hydroxide (limewater) to form an insoluble white precipitate of calcium carbonate.
7. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?
A salt and water
Acid + Alkali → Salt + Water (H⁺ + OH⁻ → H₂O).
8. Which gas is produced when a reactive metal (such as magnesium or zinc) reacts with dilute hydrochloric acid: hydrogen or oxygen?
Hydrogen
Metal + Acid → Salt + Hydrogen gas (which gives a squeaky pop with a lighted splint).
9. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?
Burette
A burette delivers variable volumes accurately to within 0.05 cm³.
10. Which salt is formed when hydrochloric acid (HCl) is neutralised by sodium hydroxide (NaOH): sodium chloride or sodium sulfate?
Sodium chloride
HCl + NaOH → NaCl (sodium chloride) + H₂O.
11. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?
Sulfate
Sulfuric acid forms sulfate salts; nitric acid forms nitrates; hydrochloric acid forms chlorides.
12. Does an alkaline (basic) solution (such as sodium hydroxide or soapy water) have a pH greater than 7 or less than 7?
Greater than 7
Alkalis (soluble bases) have pH values above 7 (from 7 to 14).

12 questions · Seed 58 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 13-15

Acids, bases & the pH scale

Take your time. Show your thinking.

1. What colour does red litmus paper turn when dipped into an alkaline solution: blue or yellow?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
2. Which solution is more strongly acidic: Solution A with pH 1, or Solution B with pH 5?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
3. Which ion is present in all aqueous alkaline solutions: hydroxide ions (OH⁻) or chloride ions (Cl⁻)?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
4. On the standard pH scale (0 to 14) at 25 °C, what is the pH of a neutral solution such as pure water: 7 or 0?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
5. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
6. What is the chemical test that confirms a gas is carbon dioxide (CO₂): it turns clear limewater cloudy (milky), or it relights a glowing splint?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
7. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
8. Which gas is produced when a reactive metal (such as magnesium or zinc) reacts with dilute hydrochloric acid: hydrogen or oxygen?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
9. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
10. Which salt is formed when hydrochloric acid (HCl) is neutralised by sodium hydroxide (NaOH): sodium chloride or sodium sulfate?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
11. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
12. Does an alkaline (basic) solution (such as sodium hydroxide or soapy water) have a pH greater than 7 or less than 7?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

12 questions · Seed 58 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 13-15

Acids, bases & the pH scale

Answers and reasoning. Review before teaching.

1. What colour does red litmus paper turn when dipped into an alkaline solution: blue or yellow?
Blue
Alkalis turn red litmus paper blue.
2. Which solution is more strongly acidic: Solution A with pH 1, or Solution B with pH 5?
Solution A with pH 1
Lower numbers on the pH scale indicate higher hydrogen-ion concentration and stronger acidity.
3. Which ion is present in all aqueous alkaline solutions: hydroxide ions (OH⁻) or chloride ions (Cl⁻)?
Hydroxide ions (OH⁻)
Alkalis dissolve in water to release hydroxide ions (OH⁻).
4. On the standard pH scale (0 to 14) at 25 °C, what is the pH of a neutral solution such as pure water: 7 or 0?
7
A pH of 7 is neutral, with equal concentrations of H⁺ and OH⁻ ions.
5. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
Red
Acids turn blue litmus paper red.
6. What is the chemical test that confirms a gas is carbon dioxide (CO₂): it turns clear limewater cloudy (milky), or it relights a glowing splint?
It turns clear limewater cloudy (milky)
CO₂ reacts with calcium hydroxide (limewater) to form an insoluble white precipitate of calcium carbonate.
7. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?
A salt and water
Acid + Alkali → Salt + Water (H⁺ + OH⁻ → H₂O).
8. Which gas is produced when a reactive metal (such as magnesium or zinc) reacts with dilute hydrochloric acid: hydrogen or oxygen?
Hydrogen
Metal + Acid → Salt + Hydrogen gas (which gives a squeaky pop with a lighted splint).
9. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?
Burette
A burette delivers variable volumes accurately to within 0.05 cm³.
10. Which salt is formed when hydrochloric acid (HCl) is neutralised by sodium hydroxide (NaOH): sodium chloride or sodium sulfate?
Sodium chloride
HCl + NaOH → NaCl (sodium chloride) + H₂O.
11. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?
Sulfate
Sulfuric acid forms sulfate salts; nitric acid forms nitrates; hydrochloric acid forms chlorides.
12. Does an alkaline (basic) solution (such as sodium hydroxide or soapy water) have a pH greater than 7 or less than 7?
Greater than 7
Alkalis (soluble bases) have pH values above 7 (from 7 to 14).

12 questions · Seed 58 · Age guidance, not curriculum certification