q1 describe briefly how rocks are weathered? ans: by physical weathering and chemical weathering
TRANSCRIPT
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Q1 Describe briefly how
rocks are weathered?
Ans:
By physical weathering and
Chemical weathering
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Q2 Which of the following substance can sublimes to form vapour on heating?
a) Stone
b) Ice
c) Iodine solid
d) Glass
Ans: c
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• Q3 Describe the steps of fractional distillation.
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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.
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Q4 Xenon is in Group VIII.
Is Xenon(Xe)stable? Why?
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• Ans: Yes. Because Xenon has an octet of
• electrons./• 8 electrons in the outermost • shell.
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Q5 Give two differences
between the properties of
Group I elements and
Group VII elements?
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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.
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Q6 Give 2 uses of noble
gases.
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• Ans. ( Textbk. P. 63 )
- Helium is used to fill airships.
- Neon is used in advertising signs.
- Argon is used to fill light bulbs.
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• 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?
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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%
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• 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.
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ANS:• It is a compound. It can be
broken down into two simpler substances, the silvery liquid and the colourless gas.
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Q9 Give three uses of limestone
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ANS:• Constructing buildings
• Building roads
• Making glass, steel, concrete, cement, paper and mortar.
• Neutralize the soil
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Q10 Give two uses of
aluminium.
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ANS:• aircraft body,overhead
power cables.
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Q11 Hydrogen is the lightest
gas, but why don’t we use it
in filling airships?
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Ans:Because it is explosive and can cause explosion.
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Q12 In which group and period does Bromine belong to ?(Br atom has 7 e- inthe outermost e- shell and has 4 e- shells)
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Ans:Period: 4Group: VII (Halogens)
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Q13 Is Bromine(Gp VII) stable or not?Why?
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Ans:Bromine is not stable as ithas only 7 e- in the outermost e- shell and does not have an octet structure.
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Q14 Is it easier for the metal
atom to gain or to lose
electrons ? Why?
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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.
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Q15 What is the meaning of
isotopes?
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Ans:Isotopes are atoms of the same element having same no. of p+ and e- but different no. of neutrons.
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Q16 In an atom, which sub-
atomic particle is positive
and which one is negative?
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Ans:Protons - positiveElectrons - negative
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Q17 State two physical
weathering?
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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.
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Q18 How to obtain pure
metal from ore?
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Ans:
First , mining of the ore ,
then concentrating the ore ,
and extraction of metal from
concentrated ore , last
purification of the impure
metal.
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Q19 How can we test for
carbonate ions and what is
the expected observation?
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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.
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Q20 How can we determine
whether a solid is a
metal or non-metal?
Please draw the
experimental set-up.
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Q21 Which metal is used to
make supersonic aircraft ?
Give 2 reasons to support
your answer.
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Ans:
Titanium.
It is because titanium is light,
corrosion resistant, strong
and malleable.
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Q22 What are the special
names of
GROUP 1
GROUP 2,
GROUP 7 &
GROUP 0 ?
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Ans:•GROUP 1: Alkali metals•CROUP 2: Alkaline earth met
als•GROUP 7: Halogens•GROUP 0: Noble gases
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Q23 What is the difference
between Weathering & Erosion?
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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.
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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 ?
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• 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.
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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.
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• Q26 Give 2 advantages of using aluminium to make overhead power cable.
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Ans:• Low density• Ductile• Very good conductor of electricit
y• Cheaper than copper
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Q27 Why the accurate
relative atomic masses of
elements are very seldom
whole numbers?
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Ans:
The elements might contain
several isotopes in different
proportions.
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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
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Q29 Which of the following
ions have the same number
of electrons as a neon
atoms? Pls try!!!!
(1) Mg2+
• (2) O2-
• (3) Cl-
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Q30 Do all noble gases have
octet of electrons?
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Ans:
No.
Except He.
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Q31 Why do elements in
group 0 rarely form
compounds?
Ans:
It is because they are octet and very stable.
They are extremely unreactive.
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Q32 Describe the formation
of sedimentary rocks?
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Ans:
They came from broken up mineral particles of other rocks, remains of plants and animals and precipitates due to chemical reactions.
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Q33 Can electrolytes
conduct electricity?
Why?
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Ans:
Yes. They can only conduct
electricity in liquid and
molten states.
It is because mobile ions are
present.
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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)
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• Q35 What are similarities of Group VII elements?
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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.