Acids and Alkalis Worksheet - KS3 - Beginner

Acids and Alkalis worksheet for KS3 (Key Stage 3 / Year 7-9 (Ages 11-14)). Beginner level science practice, aligned to the UK National Curriculum. Print-ready with answer key included.

Science•Key Stage 3 / Year 7-9 (Ages 11-14)•Acids and Alkalisbeginner

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Acids and Alkalis: pH, Indicators and Neutralisation

Key Stage 3 / Years 7–9 (ages 11–14) • Beginner

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Instructions: Work through the activities in order. Use the pH scale and indicator notes provided to support your answers, and show your reasoning where asked. Remember: laboratory chemicals must only be tested under your teacher’s instructions.

Reading the pH Scale

Use the pH scale to decide whether each substance is acidic, neutral or alkaline. Lower pH values are more acidic; higher values are more alkaline. A pH of 7 is neutral.

pH scale: 0–6 = acidic; 7 = neutral; 8–14 = alkaline.

1. A solution has pH 3. Is it acidic, neutral or alkaline?

2. A solution has pH 7. Is it acidic, neutral or alkaline?

3. A solution has pH 11. Is it acidic, neutral or alkaline?

4. Which is more acidic: a solution at pH 2 or one at pH 5?

Everyday Acids and Alkalis

Classify each familiar substance using what you know about everyday acids and alkalis. For this activity, use the typical classroom examples shown in the questions.

1. Lemon juice is acidic, neutral or alkaline?

2. Vinegar is acidic, neutral or alkaline?

3. Pure water is acidic, neutral or alkaline?

4. Soap solution is usually acidic, neutral or alkaline?

Indicators and Colour Changes

An indicator changes colour depending on whether a solution is acidic, neutral or alkaline. Use the indicator facts below; then identify each solution from its colour result.

Indicator facts: Universal indicator is red/orange in acids, green at pH 7, and blue/purple in alkalis. Litmus turns red in acids and blue in alkalis.

1. Universal indicator turns red in a solution. What type of solution is it?

2. Universal indicator is green. What is the solution’s pH?

3. Litmus paper turns blue. Is the solution acidic or alkaline?

4. Universal indicator turns purple. Is the solution acidic, neutral or alkaline?

Neutralisation: What Happens?

Neutralisation happens when an acid reacts with an alkali. In a simple neutralisation reaction, the products are a salt and water. Use that pattern to complete each question.

Model: acid + alkali → salt + water

1. Complete the word equation: hydrochloric acid + sodium hydroxide → sodium chloride + ___.

2. What type of substance reacts with an acid to neutralise it: another acid or an alkali?

3. What are the two general products of an acid–alkali neutralisation reaction?

4. A small amount of alkali is added to an acidic solution. What happens to the solution’s pH: does it tend to rise or fall?