Lemon juice makes you wince; soap feels slippery. One is an acid and the other an alkali — two families of chemicals found all over the kitchen and bathroom. In the Fizz Lab, Year 6 scientists learn to tell them apart safely, using indicators.
What your child will learn
- Name everyday acids, alkalis and neutral liquids
- Know that an indicator changes colour to show acid or alkali
- Read the pH scale: below 7 is acid, 7 is neutral, above 7 is alkali
- Know that an acid and an alkali can cancel each other out
Never taste to test
Weak acids like lemon juice and vinegar taste sour, and weak alkalis like soapy water feel slippery — but strong ones can burn. Scientists never taste or touch to find out. They use an indicator, such as litmus paper or red cabbage water, which changes colour instead.
The pH scale
The pH scale runs from 0 to 14. Pure water is neutral, at 7. Numbers below 7 are acids — the lower, the stronger. Numbers above 7 are alkalis. Mixing the right amounts of an acid and an alkali makes a neutral solution: this is neutralisation.
Example questions
Here are a few questions like the ones in the first quest. Can you solve them?
1. Which of these is an alkali?
🧼- Soapy water
- Vinegar
- Cola
- Orange juice
Show answer
Answer: Soapy water. Soap makes water alkaline, which is why it feels slippery.
2. What should you NEVER do to find out whether an unknown liquid is an acid?
- Use an indicator
- Ask a teacher
- Read the label
- Taste it
Show answer
Answer: Taste it. Unknown chemicals can be dangerous — never taste them.
3. What should you wear when testing chemicals in a lab?
🥽- Safety goggles
- Headphones
- A woolly hat
- Sunglasses
Show answer
Answer: Safety goggles. Goggles protect your eyes from splashes.
Tips for grown-ups
- Boil red cabbage, keep the purple water, and test lemon juice, vinegar and soapy water with it.
- Add bicarbonate of soda to vinegar and watch the fizz.
- Read the labels on cleaning products together and talk about the warning symbols.