Test Part A Fill in the gaps An acidic substance always contains (1) in its name. An (2) is a chemical that changes colour to tell you whether a substance is an acid or a (3). Another name for (4)/(5) is hydrogen sulfate. The proper name for hydrochloric acid is (6)/(7) or HCl. The proper name for nitric acid is (8)/(9) or (10). Red litmus paper will turn a (11) colour in a base. Blue litmus paper will turn a (12) colour in an acid. Bases are the (13) to acids. Bases are also called (14). All bases have (15) in the second part of their name. The common name for magnesium hydroxide is (16). Caustic soda, which is often used in cleaning, is really called (17)/(18). Solutions that are neither acidic or basic are called (19) solutions. In the right amounts an acid will (20) a base. When this happens a (21) is produced. Some indicators (other than litmus) are (22) (23) and (24). ph paper is a very accurate way of measuring acids and bases. ph can be measured by either a (25) or a colour. Numbers 0 5 are acidic with a colour ranging from (26) to (27). A neutral substance has the number (28). The colour for neutral is (29). A base will show either a (30) or (31) colour. The numbers for a base range from (32) to (33). ph paper tells you how weak or (34) an acid or base is,
which (35) paper doesn t do. It is possible to make an indicator out of (36) or (37) so long as these have a dark dye in them. We use acids and bases every single day. (38) is found in our stomach and is important for the digestion of proteins. Vinegar is (39), which is used to flavour and preserve foods. In lemons and oranges there is (40). Acid rain contains (41), which can kill trees and corrode buildings. The base (42) is used to make plaster and cement. Both (43) and (44) are used as household cleaners. Part B Examine the following ph scale. Answer true or false to 1 7. 1. Substance B is a base. 2. Substance A is a stronger acid than Substance B. 3. Substance D is neutral. 4. Substances D and F are bases. 5. Substance D is a weaker base than Substance E. 6. Substance F will turn ph paper red. 7. Substance C is possibly pure water.
8. Complete this word equation: acid + (a) water + (b). This is called (c). 9. On a ph chart like the one below, mark the range of: a weak acids b weak bases c strong acids d strong bases e neutral 10. Explain why you would not use: a a toothpaste with a ph of 1? b a hand cream with a ph of 14? c a detergent with a ph of 7?
11. a How does ph indicator work? b If a substance has a ph of 4, is it an acid or an alkali? c If a substance has a ph of 11, is it an acid or an alkali? d If a substance has a ph of 7, what does this mean? 12. What are the ph values of these solutions? pure water concentrated hydrochloric acid vinegar (a weak acid) concentrated sodium hydroxide ammonia solution (a weak alkali) salt water
Answers Part A 1. hydrogen 2. indicator 3. base 4. sulfuric acid 5. sulfuric acid 6. hydrogen chloride 7. hydrogen chloride 8. hydrogen nitrate 9. hydrogen nitrate 10. HNO 3 11. blue 12. red 13. opposite 14. alkalis 15. hydroxide 16. milk of magnesia 17. sodium hydroxide 18. sodium hydroxide 19. neutral 20. neutralise 21. salt 22. bromothymol blue 23. phenolphthalein 24. universal indicator 25. number 26. red 27. orange/yellow 28. 7 29. yellow
30. green/blue 31. blue/green 32. 9 33. 14 Part B 34. strong 35. litmus 36. flowers 37. vegetables 38. hydrochloric acid 39. acetic acid 40. citric acid 41. sulfuric acid 42. calcium hydroxide 43. ammonium hydroxide 44. sodium hydroxide 1. false 2. true 3. false 4. true 5. true 6. false 7. true 8. a base b salt c neutralisation 9. a 5 7 b 8 10 c 1 4 d 11 14 e ph7 10. a It s an acid. b It s a very strong base. c It s neutral. 11. a Different colour in acid and in alkali b Acid
c Alkali d It is neutral 12. Pure water ph7, conc. hydrochloric acid ph1 (actually less), vinegar about ph3, conc. sodium hydroxide ph14, ammonia ph10, salt water ph