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pH: every step is ten times
CHEM-2 Structure decides propertiesX-2 Evidence outweighs opinion
What many people think
pH 3 is only a little more acidic than pH 4.
The idea
Each step down the pH scale means ten times more hydrogen ions.
Explain it
Normal rain is about pH 5.6. In a lake at pH 4.6, many kinds of fish struggle to survive. Explain to a friend why a change of just 1 is a big deal.
Try at home
With an adult: chop red cabbage, soak it in hot water, let it cool and strain it. Add a spoon of this purple indicator to lemon juice, vinegar, tap water and baking-soda water, then line the cups up by colour and compare with the ruler. Use one clean spoon per cup and never mix cleaning products.