| 1. | Acids【酸】 have a _______________ sour taste. Alkalis【碱】 are _______________ slippery【滑】 and some of them have a _______________ bitter【苦】 taste. |
| 2. | In the laboratory【實驗室】, some commonly used acids include _______________ hydrochloric acid【鹽酸】, _______________ sulphuric acid【硫酸】 and _______________ nitric acid【硝酸】. Many of acids and alkalis are _______________ corrosive【腐蝕性的】. |
| 3. | In the laboratory【實驗室】, some commonly used alkalis include _______________ sodium hydroxide【氫氧化鈉】, _______________ ammonia solution【氨溶液】 and _______________ lime water. |
| 4. | Red cabbage leave _______________ extract【提取物】 can be used as _______________ natural indicators【天然指示劑】 to distinguish【辨別】 acids and alkalis because they contain _______________ pigments【色素】 which show different colours in acidic【酸性】 and alkaline【鹼性】 solutions【溶液】. |
| 5. | The use of certain【某些】 plant extracts【提取物】 as acid-alkali indicators【指示劑】 was first discovered【發現】 by a British scientist — _______________ Robert Boyle. |
| 6. | Acidic solutions【酸性溶液】 turn blue litmus paper【石蕊試紙】 to _______________ red while alkaline solutions【鹼性溶液】 turn red litmus paper to _______________ blue. Distilled water is _______________ neutral【中性】 — neither acidic nor alkaline. Therefore, it does not change the colour of blue or read litmus paper. |
| 7. | Different substances【物質】 have different degrees of acidity【酸度】 or alkalinity【鹼度】. Scientists use _______________ pH scale to indicate【表示】 the degree of acidity or alkalinity. |
| 8. | _______________ Neutral substances【物質】 have a pH value of 7, _______________ acidic【酸性】 substances have pH values lower than 7 and _______________ alkaline【鹼性】 substance have pH values greater than 7. |
| 9. | The pH value of a substance【物質】 can be found by using _______________ universal indicator【通用指示劑】 such as _______________ pH paper. |