F2 IS 2nd Term WS08 Answers

10.4    Acids and corrosion

i      Words to know:

	English term	Write the words again	Chinese term
1	Corrode (vb)		腐蝕 (動詞)
2	Corrosion (n)		腐蝕 (名詞)
3	Corrosive (adj)		腐蝕性的
4	‘Pop’ sound		爆鳴聲
5	Hydrogen		氫
6	Marble		大理石
7	Limestone		石灰石
8	Calcium carbonate		碳酸鈣

i      Fill in the blanks:

1             Some metals (e.g. zinc and magnesium) react with dilute acids. During the reactions, hydrogen

gas and heat are produced. The metals decrease in size gradually. Thus acids have corrosive

effects on these metals.

2           To test for hydrogen, a burning splint is put near the mouth of the test tube containing the gas. It burns

with a ‘pop’ sound if the gas is hydrogen.

3             We should not use acidic detergents to clean marble / limestone and limestone / marble

surfaces because both of them contain calcium carbonate, which are easily

corroded by acids. The reaction gives out carbon dioxide.

F2 IS 2nd term Test 01 (10-10.3) ans

2nd Term Test 01: 10.1 – 10.3

Test 10.1 – 10.3

Concept Checking (11 marks)

1	2	3	4	5	6	7	8	9	10
T	F	F	F	T	T	F	F	T	F

2.     Tea does not taste sour, but it contains acids

3.     All substances can be classified into three groups: acids, alkalis and alkaline substances.

4.     Both acids and alkalis are irritant and corrosive.

7      Table salt solution cannot turn red litmus paper blue (as it is neutral).

8.     A neutral substance has a pH value equal to 7.

10.   Some substances have pH values lower than 0 and higher than 14.

Multiple Choice (13 marks)

1	2	3	4	5	6	7	8	9	10
B	C	D	B	C	D	D	C	A	D

11	12	13	14
C	B	B	D

Fill in the Blanks

1.   (a)                            sour                          

      (b)                           lactic                         

      (c)                            citric                         

2.   (a)                   eye-wash bottle                 

      (b)                slow running water              

3.   (a)                            blue                          

      (b)                             red                           

4.   ___                      pH meter                      

5.   (a)                             low                          

      (b)                       low acidity                    

6.   (a)                   litmus paper                      

      (b)                           red                             

7.   (a)                  safety goggles                     

      (b)                        gloves                           

Short Question

(a)    He can identify dilute hydrochloric acid (1), because only it turns blue litmus paper red (1),

while the three other solutions do not change the colour of blue litmus paper (1).

(b)  He can identify distilled water (1), because it does not change the colours of both red and 

      blue litmus paper (1), while the two other solutions turn red litmus paper blue (1).          

(c)  He can identify the two remaining solutions (1), because dilute sodium hydroxide has  

      a higher pH value than dilute ammonia solution (1).                                                          

F2 IS 2nd term QZ 06 (10.3) ans

QZ 06: 10.3

Word Translation (11 marks)

i    Write down the English terms of the following Chinese terms:

	Chinese term	English term
1	天然的	Natural
2	指示劑	Indicator
3	石蕊試紙 / 溶液	Litmus paper / solution
4	酸性的 / 酸度	Acidic / acidity
5	鹼性的 / 鹼度	Alkaline / alkalinity
6	中性的	Neutral
7	通用指示劑	Universal indicator
8	程度	Degree
9	pH試紙	pH paper
10	pH值	pH value
11	pH標度	pH scale

Fill in the Blanks (13 marks)

1        Some deeply coloured plants show different colours in acids and alkalis. They can be used to make

(1)natural acid-alkali (2)indicator.

2        If something turns blue (3)litmus paper red, it is said to be (4)acidic.

3        Distilled water does not change the colours of both blue and red litmus paper. It is said to be (5)neutral.

4    (6)Alkaline substances turn red litmus paper blue but do not change the colour of blue litmus paper.

5    (7)Universal indicator can show the degree of acidity or (8)alkalinity of a substance. Its paper form is called (9)pH paper.

6     The scale for measuring acidity or alkalinity is called (10)pH scale. An acid has a (11)pH value smaller than 7 while that of an alkali is greater than 7.

5     The lower the pH value, the more (12)acidic a substance is;

       The higher the pH value, the more (13)alkaline it is.

Challenging Questions (Bonus 2 marks)

1.      State a common food which as a pH value lowers than 7.

Lemon (OR any other reasonable acidic food)

2.      If sodium hydroxide is mixed with universal indicator, what happens?

The indicator turns blue or violet.