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.

New variation Try interactive challenge Browse templates

Age band:Ages 13-15 Ages 16-18

Choose “Save as PDF” to keep a copy. Use your browser’s paper setting for A4 or Letter.

Worksheet StudioPractice pack · Ages 13-15

Acids, bases & the pH scale

Take your time. Show your thinking.

1. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
2. 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
3. What weak organic acid gives vinegar its sour taste: ethanoic (acetic) acid or nitric acid?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
4. 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
5. What is the chemical test that confirms a gas is oxygen (O₂): it relights a glowing wooden splint, or it turns limewater milky?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
6. Which ion is released by all Arrhenius acids when dissolved in aqueous solution: hydrogen ions (H⁺) or hydroxide ions (OH⁻)?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
7. 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
8. 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
9. 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
10. 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
11. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
12. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

12 questions · Seed 104729 · 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 weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?
Citric acid
Citrus fruits contain citric acid.
2. 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.
3. What weak organic acid gives vinegar its sour taste: ethanoic (acetic) acid or nitric acid?
Ethanoic (acetic) acid
Vinegar is a dilute aqueous solution of ethanoic (acetic) acid.
4. 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.
5. What is the chemical test that confirms a gas is oxygen (O₂): it relights a glowing wooden splint, or it turns limewater milky?
It relights a glowing wooden splint
Pure oxygen supports rapid combustion and relights a glowing splint.
6. Which ion is released by all Arrhenius acids when dissolved in aqueous solution: hydrogen ions (H⁺) or hydroxide ions (OH⁻)?
Hydrogen ions (H⁺)
Acids produce aqueous hydrogen ions (H⁺ / H₃O⁺) in water.
7. 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.
8. 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).
9. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
Red
Acids turn blue litmus paper red.
10. 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).
11. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?
10
pH = −log₁₀[H⁺], so each whole unit decrease represents a tenfold increase in [H⁺].
12. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?
Colourless in acid and pink in alkali
Phenolphthalein is colourless below pH 8.2 and turns pink-magenta in alkaline solutions.

12 questions · Seed 104729 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 13-15

Acids, bases & the pH scale

Take your time. Show your thinking.

1. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
2. 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
3. What weak organic acid gives vinegar its sour taste: ethanoic (acetic) acid or nitric acid?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
4. 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
5. What is the chemical test that confirms a gas is oxygen (O₂): it relights a glowing wooden splint, or it turns limewater milky?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
6. Which ion is released by all Arrhenius acids when dissolved in aqueous solution: hydrogen ions (H⁺) or hydroxide ions (OH⁻)?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
7. 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
8. 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
9. 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
10. 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
11. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
12. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

12 questions · Seed 104729 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 13-15

Acids, bases & the pH scale

Answers and reasoning. Review before teaching.

1. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?
Citric acid
Citrus fruits contain citric acid.
2. 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.
3. What weak organic acid gives vinegar its sour taste: ethanoic (acetic) acid or nitric acid?
Ethanoic (acetic) acid
Vinegar is a dilute aqueous solution of ethanoic (acetic) acid.
4. 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.
5. What is the chemical test that confirms a gas is oxygen (O₂): it relights a glowing wooden splint, or it turns limewater milky?
It relights a glowing wooden splint
Pure oxygen supports rapid combustion and relights a glowing splint.
6. Which ion is released by all Arrhenius acids when dissolved in aqueous solution: hydrogen ions (H⁺) or hydroxide ions (OH⁻)?
Hydrogen ions (H⁺)
Acids produce aqueous hydrogen ions (H⁺ / H₃O⁺) in water.
7. 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.
8. 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).
9. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
Red
Acids turn blue litmus paper red.
10. 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).
11. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?
10
pH = −log₁₀[H⁺], so each whole unit decrease represents a tenfold increase in [H⁺].
12. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?
Colourless in acid and pink in alkali
Phenolphthalein is colourless below pH 8.2 and turns pink-magenta in alkaline solutions.

12 questions · Seed 104729 · Age guidance, not curriculum certification