The Chemistry of Lemons and Soap
📖 The Chemistry of Lemons and Soap
The pH scale runs from 0 to 14, but it is not a regular ruler where each gap is equal. Each step is actually ten times the change in hydrogen ion concentration of the previous one. So pH 3 is not slightly more acidic than pH 4 — it has ten times more H⁺ ions. And pH 2 has one hundred times more H⁺ ions than pH 4. This is why small changes in pH number can mean enormous differences in how acidic a solution really is.
When an acid dissolves in water, it releases hydrogen ions (H⁺) into the solution. These tiny, positively charged particles are what make acids behave the way they do — they are responsible for the sour taste of citric acid, the corrosive nature of concentrated acids, and the reactions with metals and carbonates. The m
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🧠 Memory Aids
Acids and Alkalis: "HAcids = H⁺ ions. Alkalis = OH⁻ ions." The letter A connects both to their ions.
Indicator colours (three key ones):
- Litmus: Red in acid, Blue in alkali — remember "Red = Acidic, Blue = Alkaline"
- Phenolphthalein: Colourless → Pink in alkali — "Phenol turns Pink in base"
- Methyl orange: Red in acid → Yellow in alkali — "Methyl goes RED when angry (acidic)"
pH scale anchors: 0 = most acidic (stomach acid), 7 = neutral (pure water), 14 = most alkaline (bleach). Everything else falls between these reference points.
The three common acids: "HCl, H₂SO₄, HNO₃" — Hydrochloric, Sulfuric, Nitric. Mnemonic: "Hard Students Never fail" (HCl, H₂SO₄, HNO₃).
Now try it yourself
Quiz · Question 1 of 25
Which ion do acids produce when dissolved in water?
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