Unit 10 Unit 10 Summary check-point Unit 10 Unit 10 Summary check-point

Acids & alkalis in daily life p.57 1 Acids taste ______ (a) but alkalis taste ______ (b). sour bitter 2 The colour of red cabbage extract is ______ (a) in acids & ________ (b) in alkalis. is ______ (a) in acids & ________ (b) in alkalis. red green

3 Some plant extracts contain pigments that can change colour in acids & alkalis. They can be used as ______________________ (a). natural indicators

4 The commonly used laboratory _________ (a) include hydrochloric acid, nitric acid and sulphuric acid. The commonly used laboratory __________ (b) include sodium hydroxide & ammonia solution. 4 The commonly used laboratory _________ (a) include hydrochloric acid, nitric acid and sulphuric acid. The commonly used laboratory __________ (b) include sodium hydroxide & ammonia solution Laboratory acids & alkalis alkalis acids acids

5 We should take the necessary ___________________ (a) when handling acids & alkalis. We handling acids & alkalis. We must use them carefully. must use them carefully. 6 Common indicators used in the laboratory are _________ (a) & __________________ (b). laboratory are _________ (a) & __________________ (b). litmus universal indicator safety precautions p.58

7 Blue litmus turns ______ (a) in acids. Red litmus turns ______ (b) in alkalis. 7 Blue litmus turns ______ (a) in acids. Red litmus turns ______ (b) in alkalis. red blue 8 Universal indicator changes to _____ (a) in acids & ______ (b) in alkalis with a series of colours _____ (a) in acids & ______ (b) in alkalis with a series of colours in between. It is green in colour in between. It is green in colour in _________ (c) substances. in _________ (c) substances. redblue neutral

9 The _________ (a) tells the degree of acidity & alkalinity of substances. The pH value ranges from_____ (b) to ____ (c). > The pH value of _________ (d) > The pH value of _________ (d) substances is below 7. substances is below 7. > The pH value of _________ (e) > The pH value of _________ (e) substances is 7. substances is 7. > The pH value of _________ (f) > The pH value of _________ (f) substances is above 7. substances is above 7. pH scale acidic neutral alkaline 14 0

10 It is important for the different parts of our body to maintain their ________ (a) pH levels so that our body can function properly. For plants, the availability of nutrients depend on the acidity or alkalinity of the ______ (b) Importance of keeping the right pH proper soil 11 Many daily used products like cosmetics & personal care products show their ___________ (a) on their packs. cosmetics & personal care products show their ___________ (a) on their packs. pH values

12 We can test for ______________ (a) by placing a burning splint at the mouth of the test-tube full of the gas. It gives out a ‘pop’ sound The corrosive effect of acids hydrogen gas 13 Dilute acids react with some metals to give _____________ (a). The acids are __________ (b) to these metals. to give _____________ (a). The acids are __________ (b) to these metals. hydrogen corrosive

14 Dilute acids also react with building materials made of _______________ materials made of _______________ (a) to give _______________ (b). That (a) to give _______________ (b). That is why acids corrode our buildings is why acids corrode our buildings & statues. & statues. calcium carbonate carbon dioxide marble limestone sandstone

15 The average pH value of rainwater is about ______ (a) because _______________ (b) in the air can dissolve in it. The pH of acid rain is below ______ (c) 。 carbon dioxide Acid rain —— the invisible threat

16 _________ (a) is formed when acidic gases like _________________ (b) & gases like _________________ (b) & _______________ (c) dissolve in the _______________ (c) dissolve in the rainwater. The acidic gases are given off from factories, power stations & vehicles. rainwater. The acidic gases are given off from factories, power stations & vehicles. sulphur dioxide nitrogen oxides acid rain

17 The harmful effect of acid rain is slow but destructive. It _________ (a) slow but destructive. It _________ (a) our buildings & statues. It can also our buildings & statues. It can also ___________ (b) in our rivers, lakes ___________ (b) in our rivers, lakes & the sea. It can affect the _______ & the sea. It can affect the _______ __________ (c) by turning the soil __________ (c) by turning the soil acidic & toxic. acidic & toxic. corrodes destroy life 18 We can help reduce air pollution by using ________ (a) more efficiently. energy p.59growth of plants

19 Acids can be used to _________ (a) food because it can stop the food because it can stop the growth of micro-organisms. growth of micro-organisms Everyday uses of acids & alkalis of acids & alkalis preserve 20 _________ (a) contains acetic acid and is commonly used for food preservation. Vinegar

21 Fruits like apple, banana, pear and peach turn brown when they are cut and left in the air for a period of time. Acids can prevent fruits from ___________ (a) 。 browning 22 Acids & alkalis are commonly used as ___________________ (a). For as ___________________ (a). For example, hydrochloric acid is used example, hydrochloric acid is used in toilet cleansers, caustic soda in toilet cleansers, caustic soda in oven cleansers and ammonia in oven cleansers and ammonia solution as window cleansers. solution as window cleansers. cleansing agents

23 Acids & alkalis _____________ (a) each other in a chemical reaction each other in a chemical reaction called ______________ (b). In called ______________ (b). In this reaction, _____ (c) & ______ (d) this reaction, _____ (c) & ______ (d) are formed. are formed. neutralize saltwater neutralization

24 We can make use of neutralization to solve many daily problems. to solve many daily problems. Examples are ： Examples are ： > Use of ___________ (a) to treat > Use of ___________ (a) to treat stomach-ache stomach-ache > Use of acids or alkalis to treat wasp, bee, mosquito & ant stings > Use of acids or alkalis to treat wasp, bee, mosquito & ant stings > Neutralization of acidic & alkaline > Neutralization of acidic & alkaline industrial wastes before industrial wastes before _________ (b) _________ (b) antacid disposal

25 Acids & alkalis should be handled carefully because they are _______________ (a). corrosive Safety matters related to the use of acids & alkalis the use of acids & alkalis

26 ____________ (a) acid is a solution that contains a high proportion of acid in water. _____________ (b) alkali is a solution that contains a high proportion of alkali in water. They are much more ___________ c) than dilute acids & alkalis. Concentrated corrosive Concentrated

27 Concentrated acids and alkalis give out heat on __________ (a). We must dilute concentrated acids & alkalis by adding them to water, but not by adding water to them. We must wear protective clothes, safety goggles & gloves when doing so. dilution water concentrated acid / alkali