Neutralisation in daily life

Ant bite. Keerthi had her hand on a tree trunk when a red ant bit her. The skin went red and stung. An ant injects an acid called formic acid. Her brother rubbed on moist baking soda, a base, which neutralised the acid, and the pain eased.

Soil. A farmer wrote to the Farmer's Portal that his plants were not growing well. Too much chemical fertiliser had made his soil acidic.

And if the soil is neutral but plants are still weak, the soil may simply be short of nutrients.

Factory waste. Gurbir lives near an industrial area, and the fish in his neighbourhood lake are dying out. Waste from factories may be the cause. If the waste is acidic, factories should add basic substances to neutralise it before letting it into the lake.

You use neutralisation yourself every day. Germs in your mouth break down bits of food and make acids that harm your teeth. Toothpaste is basic, so brushing neutralises them. And a tablet for a burning stomach, an antacid, is a base too.

Now the science-fair trick. One possibility: the paper was written on with soap solution (a base) that dried invisible, and the spray was turmeric solution. Wherever the soap was, the turmeric turned red, and the words appeared.