Acids, Bases and Indicators
Class 7 Science: acids, bases and salts (natural indicators)
Test lemon juice, soap, baking soda and more with litmus, turmeric and China rose. Watch the colours change, then sort each one as an acid, a base or neutral.
Words to know
- Acid
- A substance that tastes sour and turns blue litmus red, like lemon juice and vinegar.
- Base
- A substance that feels soapy and turns red litmus blue, like soap and baking soda.
- Indicator
- A substance that shows by its colour whether something is an acid or a base.
- Litmus
- A natural indicator made from lichens, used as red or blue paper strips.
- Neutral
- Neither acidic nor basic, like sugar water and salt water. It changes no indicator.
Quick check
Answer 3 questions to check what you learned.
Try at home
Rub a little turmeric paste on white paper and let it dry. Put a drop of soap water on it. What colour does it turn? Try lemon juice too.