Turns blue litmus paper red.
Turns red litmus paper blue.
Changes neither paper — like tap water, sugar solution.
Generally tastes sour — lemon juice, amla juice, tamarind water, vinegar.
Often feels soapy or slippery, tastes bitter — like baking soda. (Bitterness alone isn't proof: bitter gourd isn't basic.)
Turns red.
Turns green. Beetroot, cabbage, turmeric, and jamun extracts also work.
Some substances change their odour rather than colour in acidic or basic conditions.
Onion-soaked cloth changes smell with acids or bases — useful when a colour change can't be seen.
Acid: blue → red. Base: red → blue. Neutral: no change.
Acid: red. Base: green. Neutral: no change.
Acid: no change. Base: turns red. Neutral: no change.
Injects acidic formic acid. Moist baking soda neutralises it and eases the pain.
From excess fertiliser, treated with lime — a base.
Acidic waste is neutralised with a base before release, protecting aquatic life.
A natural dye, used as an acid-base indicator.
Shows different colours in acids and bases.
Turns blue litmus red; generally sour.
Turns red litmus blue; often soapy, bitter.
Changes neither litmus paper.
Changes smell in acid or base.
Acid + Base → Salt + Water + Heat.