Recently, I have been learning about indicators, chemicals that scientists use to test for other chemicals. Yesterday, Mum made a red cabbage indicator to test for acidic, neutral and alkaline substances. If the substance turns the indicator red/pink it is an acid, if it is a alkaline the indicator will turn blue/green. If the purple indicator didn’t change the substance is neutral.
The first item I tested was the smelly vinegar. Thanks to the scent and my knowledge of all acids being sour, I guessed the vinegar would be an acid. I was correct!
The second substance I tested was lemon juice. After I put the indicator in it turned pink. This indicated it was an acid.
Next up was the water. Mum had said she used water to make the indicator, so I assumed it would be neutral. The indicator didn’t change when I added it to the water, confirming my theory.
Then, I tested the baking soda to discover it was our first alkali.
The milk turned to a lavender colour, but it is actually a weak acid. The milk didn’t change to red or pink because our indicator wasn’t sensitive enough.
The penultimate substance was the soap. On contact, the indicator turned magenta, indicating that the soap was a weak acid.
Finally, we tested carbon dioxide. When we breathe out we produce carbon dioxide, so Mum and I blew through a straw into the indicator. Carbon dioxide is the same case as the milk, except the indicator didn’t change colour at all.