Students will understand that the pH scale ranges from 1 (acid) to 7 (neutral) to 14 (basic). They will understand that acids release a hydrogen ion in solution and alkaline substances release an hydroxide ion. Substances can be tested using an acid-base indicator such as litmus paper or purple cabbage indicator. The colour change that occurs is another example of a chemical reaction.
Students will make an acid-base indicator by boiling red cabbage and straining the liquid. They will then test a range of household substances, including cleaning products, vinegar and lemon juice and determine whether they are acids or bases. Students will then use indicator paper to check their results and arrange the substances from low pH (most acidic) to high pH (most basic).
Our assessment for this unit of work will be a test on Thursday during period 5. Use Pages 76 and 77 of your textbook for revision. You may like to try this quiz at Quiz Revolution. These videos at How Stuff Works are also good revision for the test.
Seven Reactions that will fascinate your science class – Five of these reactions are chemical reactions (what are the indicators for a chemical reaction?) and two are physical changes. Which two are physical changes?
Sulfuric acid in sugar (video) – What are the signs that this is a chemical reaction?
Sodium metal in water (video) – What are the signs that this is a chemical reaction?