![]() Below is a colour chart showing the range of colours for universal indicator and the pH values they correspond to. Universal indicator has different colours at different pH values. The higher the pH value, the more strongly basic the substance.Īnother useful thing we learnt in the previous chapter is that we can use universal indicator to measure the pH of a solution. The lower the pH value, the more strongly acidic the substance. If we want to know whether something is an acid or a base, we can measure its pH: In the previous chapter we learnt about a new concept, namely pH. Hypothesising, preparing, comparing, measuring, recording, plotting graphs Investigation: The reaction between calcium carbonate (chalk) and hydrochloric acid Hypothesising, preparing, measuring, observing, measuring, recording, plotting graphsĦ.4 The general reaction of an acid with a metal carbonate (1.5 hours) ![]() Investigation: The reaction between sodium hydroxide and hydrochloric acid Hypothesising, preparing, observing, measuring, recording, plotting graphsĦ.3 The general reaction of an acid with a metal hydroxide (1.5 hours) Investigation: The reaction between magnesium oxide and hydrochloric acid Observing, reading, researching, interpreting, analysing, summarisingĦ.2 The general reaction of an acid with a metal oxide (1.5 hours) Hypothesising, measuring, preparing, observing, comparing, recording, plotting graphs Investigation: The reaction between vinegar and baking soda Take note that although there is no section specifically named 'Applications' as indicated in CAPS, this content has rather been dealt with under other sections where it is more appropriate. If questions arise around the issue you could point out that the salts they will encounter in this chapter mayīe neutral substances, but that this is not true of all salts. Our suggestion is that you simply refrain from calling salts 'neutral substances'. The chemistry required for learners to understand this is beyond them at this stage and will only be dealt with in Physical Sciences in Grade 12. The reason is that not all salts are 'neutral substances' in fact most salts have acid-base properties of their own. pH = 7) under very special circumstances. Even if equivalent quantities (stoichiometric quantities) of the acid and base are mixed - which would imply that both have been neutralised - the resulting solution will only be neutral (i.e. However, this does not mean that the mixture of an acid with a base will be a neutral solution and you should avoid language that reinforces this notion.
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