📚 Part 1: Key Vocabulary Matching

1. Match each term to its correct definition by drawing a line:

pH scale

Acid

Alkali

Neutral

Indicator

A substance that changes colour to show pH

A scale from 0-14 that measures acidity

A substance with pH greater than 7

A substance with pH less than 7

A substance with pH equal to 7

2. Complete the pH scale by filling in the missing numbers:

0 --- 2 --- ____ --- 6 --- ____ --- 8 --- 10 --- ____ --- 14

Acidic: 0-6 | Neutral: ____ | Alkaline: ____-14

🔬 Part 2: Understanding pH and Indicators

3. What colour does red litmus paper turn in an alkali?

Red

Blue

Green

No change

4. What colour does blue litmus paper turn in an acid?

Blue

Red

Yellow

No change

5. Complete this table for testing household substances:

Substance	Universal Indicator Colour	Estimated pH	Acid, Neutral or Alkali?
Lemon juice	_____________	_____	_____________
Pure water	_____________	_____	_____________
Baking soda solution	_____________	_____	_____________
Vinegar	_____________	_____	_____________

✏️ Part 3: Explaining How Indicators Work

6. Explain in your own words how indicators help us identify acids and alkalis:

7. Why is it useful to know if a substance is acidic or alkaline? Give one example:

8. Challenge Question: Universal indicator shows many different colours, but litmus paper only shows two colours. Explain why universal indicator is more useful for measuring pH:

9. Extension Challenge: Research question - Why do you think indicators change colour when they meet acids or alkalis? What happens to the indicator molecules?