Indicators you can smell
A chopped onion has a strong smell. A base can remove that smell. Test each jar with an onion strip.
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The idea
Some things change in smell, not colour, with an acid or base. They are olfactory indicators. Olfactory means about smell. Onion is one.
Step 1 of 4
- Two onion strips. Both have a strong smell.
- A drop of acid on the first. The smell stays strong.
- A drop of base on the second. The smell fades.
- A fading smell points to a base.
An olfactory indicator changes its smell. Onion smell stays in an acid and fades in a base.
A teacher does this test. Never sniff an unknown liquid.