MediumChemistryHigh School (9–10)GeneralAcids, Bases and Salts › pH and NeutralisationAcids, Bases and Salts › Acids and BasesConceptual
Explain how tooth decay begins, and why brushing with toothpaste helps.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Explain how tooth decay begins, and why brushing with toothpaste helps. At what pH does the danger begin?
Need a reminder? The key ideaShow
Stomach acid is hydrochloric acid of pH about ; antacids are mild bases. Tooth enamel dissolves below pH ; toothpaste is basic. Bee and ant stings are acidic, so a mild base helps. Acidic soil gets lime.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Bacteria break down sugar and food left on the teeth and make acids.
Step 2. Below pH , the acid starts to dissolve the enamel, which is calcium phosphate.
Step 3. Toothpaste is basic, so it neutralises the acid, and brushing removes the food.
Answer: danger below pH .
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