Q1 Describe briefly how

rocks are weathered?

Ans:

By physical weathering and

Chemical weathering

Q2 Which of the following substance can sublimes to form vapour on heating?

a) Stone

b) Ice

c) Iodine solid

d) Glass

Ans: c

• Q3 Describe the steps of fractional distillation.

Answer: in textbook page 57.

• The components of air can be separated to their differences in boiling points.

• The air is first liquefied by repeated cooling and compression. The liquid air is warmed up slowly. Different gases in air boil at diff. Temp. and we can collect them one by one.

Q4 Xenon is in Group VIII.

Is Xenon(Xe)stable? Why?

• Ans: Yes. Because Xenon has an octet of

• electrons./• 8 electrons in the outermost • shell.

Q5 Give two differences

between the properties of

Group I elements and

Group VII elements?

Ans: • Reactivity of Group I elements

increases down the group but Group VII elements decreases down the group, and

• Group I elements are reactive metals while Group VII elements are poisonous non-metals.

Q6 Give 2 uses of noble

gases.

• Ans. ( Textbk. P. 63 )

- Helium is used to fill airships.

- Neon is used in advertising signs.

- Argon is used to fill light bulbs.

• Q7 An element X occurs naturally as a mixture of two isotopes. The relative isotopic masses of the two isotopes are 63.0 and 65.0. The relative atomic mass of X is 63.6. What is the percentage abundance of the two isotopes?

Let the relative abundance of 6363X and X and 6565X be y% X be y% and (100-y)% respectively.and (100-y)% respectively.

Relative atomic mass of X =Weighted average Relative atomic mass of X =Weighted average mass of the isotopesmass of the isotopes 63.6 = 63.6 = 63 xy + 65 x (100 - y)63 xy + 65 x (100 - y) 100 100 6360 = 63y + 6500 – 65y 6360 = 63y + 6500 – 65y y = 70y = 70

Therefore the relative abundance of Therefore the relative abundance of 6363X is 70% X is 70% while that while that 6565X is 30%X is 30%

• Q8 A chemist had a red powder. When the red powder was heated strongly, a silvery liquid and a colourless gas formed. Is the red powder an element or a compound? Explain your answer.

ANS:• It is a compound. It can be

broken down into two simpler substances, the silvery liquid and the colourless gas.

Q9 Give three uses of limestone

ANS:• Constructing buildings

• Building roads

• Making glass, steel, concrete, cement, paper and mortar.

• Neutralize the soil

Q10 Give two uses of

aluminium.

ANS:• aircraft body,overhead

power cables.

Q11 Hydrogen is the lightest

gas, but why don’t we use it

in filling airships?

Ans:Because it is explosive and can cause explosion.

Q12 In which group and period does Bromine belong to ?(Br atom has 7 e- inthe outermost e- shell and has 4 e- shells)

Ans:Period: 4Group: VII (Halogens)

Q13 Is Bromine(Gp VII) stable or not?Why?

Ans:Bromine is not stable as ithas only 7 e- in the outermost e- shell and does not have an octet structure.

Q14 Is it easier for the metal

atom to gain or to lose

electrons ? Why?

Ans:It is easier for the metal atoms to lose e- than to gain e- to form ions (cat- or an-).Why?It requires less energy.

Q15 What is the meaning of

isotopes?

Ans:Isotopes are atoms of the same element having same no. of p+ and e- but different no. of neutrons.

Q16 In an atom, which sub-

atomic particle is positive

and which one is negative?

Ans:Protons - positiveElectrons - negative

Q17 State two physical

weathering?

Ans:

1. Weathering by temperature

changes: when rocks get hot in

daytime but cool down quickly at

night.

2. Weathering by frost action :when

water freezes and expands to form

ice, the rocks break apart.

Q18 How to obtain pure

metal from ore?

Ans:

First , mining of the ore ,

then concentrating the ore ,

and extraction of metal from

concentrated ore , last

purification of the impure

metal.

Q19 How can we test for

carbonate ions and what is

the expected observation?

Ans:Add the sample into a test tube of hydrochloric acid and use the limewater to test for the gas.If the limewater turns milky, that means carbon dioxide is present. Then the sample must contain carbonate ion.

Q20 How can we determine

whether a solid is a

metal or non-metal?

Please draw the

experimental set-up.

Q21 Which metal is used to

make supersonic aircraft ?

Give 2 reasons to support

your answer.

Ans:

Titanium.

It is because titanium is light,

corrosion resistant, strong

and malleable.

Q22 What are the special

names of

GROUP 1

GROUP 2,

GROUP 7 &

GROUP 0 ?

Ans:•GROUP 1: Alkali metals•CROUP 2: Alkaline earth met

als•GROUP 7: Halogens•GROUP 0: Noble gases

Q23 What is the difference

between Weathering & Erosion?

Ans:Weathering of rocks is the slow process in which exposed rocks are broken down into smaller pieces, but erosion of rocks is slow process in which weathered rock pieces are transported away by gravity, wind and water.

Q24 The element bromine

has two isotopes and

relative atomic mass of

79.9.

What is the difference in

structure between the

isotopes of bromine ?

• Q25 For each of the common changes listed below, determine whether it is a physical change or chemical change. Give you reason(s) for each case.

• a) Making alcohol form grapes.• b) Making ice from water.• c) Electrolysis of water.

Ans:a. Chemical change. A new substance (al

cohol) is formed from grape.b. Physical change. No new substances i

s formed; water is only changed from liquid to sol

id state.c. Chemical change. New substance are f

ormed. They are hydrogen and oxygen.

• Q26 Give 2 advantages of using aluminium to make overhead power cable.

Ans:• Low density• Ductile• Very good conductor of electricit

y• Cheaper than copper

Q27 Why the accurate

relative atomic masses of

elements are very seldom

whole numbers?

Ans:

The elements might contain

several isotopes in different

proportions.

Q28 Why is the electronic

arrangement of Rubidium

(Rb) is 2,8,18,8,1 instead of

2,8,18,9?  (It's so strange...)

Ans:

because … you will learn it in F6

Q29 Which of the following

ions have the same number

of electrons as a neon

atoms? Pls try!!!!

(1) Mg2+

• (2) O2-

• (3) Cl-

Q30 Do all noble gases have

octet of electrons?

Ans:

No.

Except He.

Q31 Why do elements in

group 0 rarely form

compounds?

Ans:

It is because they are octet and very stable.

They are extremely unreactive.

Q32 Describe the formation

of sedimentary rocks?

Ans:

They came from broken up mineral particles of other rocks, remains of plants and animals and precipitates due to chemical reactions.

Q33 Can electrolytes

conduct electricity?

Why?

Ans:

Yes. They can only conduct

electricity in liquid and

molten states.

It is because mobile ions are

present.

Calcium carbonate

Calcium hydroxide

Calcium oxide

Calcium chloride

Stage 3

Stage1

Stage 2

heating

Q34:

AI)Suggest how calcium oxide can be converted to calcium chloride in stage 3?

II)Write a word equation refer to part AI)

• Q35 What are similarities of Group VII elements?

Ans:

-All are poisonous non-metals.

-All are reactive.

-All have similar chemical properties. For examples, their aqueous solutions are turned colourless by aqueous sodium sulphite solution.