I gave acid base lessons for the star kids club students, 2 weeks back and I would like to share it with you. The lessons went as follows……
Every liquid is either acid or base.
Acids are generally,
- Sour in taste
- They break down and corrode things
- Strong and needs warning
- Acids lose their acidity when they are combined with bases
- There are also harmless weak acids needed for our survival. Vitamin C (ascorbic acid) is naturally find together with citric acid in oranges and lemons.
- Acids have lots of hydrogen ions.
Bases are generally,
- Bitter in taste
- Solution will feel soapy
- Many bases are insoluble in water but however some bases dissolve in water and we call them alkali
- Bases reacts with acids and neutralise them.
- Bases have lots of hydroxide ions.
We can’t taste all the liquids , to identify them as whether an acid or base. So we have a special type of substance which identifies acid and base by changing its colour. These substances are called indicators.
Litmus, turmeric,purple cabbage and China rose petals are some of the naturally occurring indicators.
Scientists use pH scale to measure how much acidic or basic, a liquid is. The pH scale measures the acidity, the same way that a centimetre scale measures length.
PH is a number from 0 to 14.
- PH 0 to 6 is acid, 0 being the strongest acid.
- PH 8 to 14 is base, 14 being the strongest base.
- And pH 7 is neutral
I explained all this to the children and we did acid base testing of various liquids like vinegar, baking soda, lemon juice, tomato juice, shampoo, water, milk, dishwasher liquid, bleach, cola etc with the purple cabbage water as indicator and we interpreted each liquid in to either acid or base with the colour change and the ph scale.
All the children were given chances to add the liquids to the indicator in the test tube.
We also tested the liquids with litmus paper.
Then I showed them the acid base neutralisation reaction with vinegar and baking soda and we saw the balloon burst with the carbon dioxide gas. And we could make out the salt and water remaining in the bottle. I forgot to take a picture of that, so I am sharing a picture from the net.
Thanks to One Little Project
Then we discussed about the acids and bases found in our daily life.