rocks are weathered?

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29 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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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
63
X and
65
X be y%
and (100
-
y)% respectively.

Relative atomic mass of X =Weighted average
mass of the isotopes


63.6 =
63 xy + 65 x (100
-

y)


100


6360 = 63y + 6500


65y


y = 70


Therefore the relative abundance of
63
X is 70%
while that
65
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
-

in

the outermost e
-

shell and

has 4 e
-

shells)



Ans:

Period: 4

Group: VII (Halogens)



Q13 Is Bromine(Gp VII)

stable or not?

Why?



Ans:

Bromine is not stable as
it

has 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
-

positive

Electrons
-

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 metals


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
(alcohol) is formed from grape.

b. Physical change. No new
substances is formed;


water is only changed from liquid to
solid state.

c. Chemical change. New substance
are formed. 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
electricity


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) Mg
2+


(2) O
2
-


(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
.