S4.7.5 For the adult
Acids, bases and salts
Why does vinegar fizz when I add baking soda?
What this chapter teaches
An acid makes H⁺ ions in water and an alkali makes OH⁻ ions. An acid with a metal makes a salt and hydrogen, with a base a salt and water, and with a carbonate a salt, water and carbon dioxide. Each step on the pH scale is ten times more or fewer H⁺ ions, and neutralisation is H⁺ + OH⁻ → H₂O.
Three questions to ask
There is no one right wording. Listen for the idea.
- What are the three reactions of an acid, and what does each make?
- Why is a solution of pH 3 ten times more acidic than one of pH 4?
- What colour change would you expect with red cabbage and vinegar, and why?
After the chapter, the learner can
- Write equations for acids reacting with metals, bases and carbonates
- Explain the pH scale in terms of hydrogen ions
What they copy into their notebook
Acid + metal makes salt and hydrogen. Acid + base makes salt and water. Acid + carbonate makes salt, water and carbon dioxide. Each pH step is ten times the H⁺.