Year 8 Chemistry – Revision 2014
1. Matter is anything with a m _ _ _
are smallest particles in a substance.
2. There are 3 states of matter
Name: ________________________
and a v
_ _ _ _ _ _ . Matter is made of
Atoms
s _ _ _ _ , l _ _ _ _ _ and g _ _ .
3. A substance can change its states when it is heated or cooled.
A solid (e.g. Ice) will change to a liquid (eg. Liquid water) when it is warmed by the
surrounding air. This process is known as m
______.
4. A liquid (eg. Water) will change to a gas (eg. Steam) when it is heated. This process is called
V _ _ _ _ _ _ _ _ _ _ _. Boiling is the vigorous evaporation of water to steam.
5.
C _ _ _ _ _ _ _ _ _ _ _ is a process in which a gas changes into a liquid.
(eg. The gaseous cloud becomes rain).
6.
Sublimation is a special process in which a s _ _ _ _ changes into a g _ _ directly
without going through a l _ _ _ _ _ state. Eg. Black Iodine solid will change into a
p _ _ _ _ _ vapour on heating.
Eg. Solid carbon dioxide (= d
carbon dioxide is not existed.
__
i _ _ ) will change to carbon dioxide gas. Liquid
7. Complete the following diagram with the following 6 processes:
condensation, solidification, sublimation, vaporisation, melting,
freezing
SOLID
GAS
LIQUID
8. Chemicals can be divided into Pure substances or m
be either e
_______
or
_ _ _ _ _ _ _. Pure substances can
c _ _ _ _ _ _ _ _.
9. A mixture is a substance that consists of 2 or more substances. These substances can be
separated by physical means. Eg. Filtration, Chromatography, Magnetic separation, etc.
10. An element is a pure substance which consists of only one type of a _ _
broken down into simpler substance. Eg. Sodium, Iron, Helium, Sulphur.
_ _. It can’t be
11. There are 117 elements found on Earth. About 90 of them are naturally occurred and others are
a _ _ _ _ _ _ _ _ _ _ made in the laboratory.
12. The p _ _ _ _ _ _ _ table is a tabular arrangement of the chemical elements by atomic
number, starting with hydrogen in the upper left-hand corner and continuing in ascending order
from left to right, arranged in columns according to similar chemical properties.
13. Standard chemical symbols are used worldwide to represent these elements. Many symbols are
derived from the elements in Latin or Greek.
Hydrogen _____
Oxygen _____
Sulphur _____
Copper
_____
Iron _____
Aluminium _____
Chlorine _____
Bromine _____
Helium _____
Mercury _____
Fluoride _____
Calcium _____
Magnesium _____
Sodium _____
Potassium _____
Lead
_____
Nitrogen _____
Uranium _____
Carbon _____
Zinc
_____
14. A compound is a pure substance which consists of two or more e _ _ _ _ _ _ _ or atoms
chemically bound together.
15. A molecule is the smallest part of a chemical that is made of 2 or more atoms joined together.
If the atoms are the same, it is an element, eg. O2, N2; if they are different kinds of atoms, it is a
compound, eg. CuSO4
Compounds
Chemical Formula
Elements in the compounds
Sodium chloride
NaCl
Copper sulphate
Hydrogen sulphide
Magnesium oxide
Carbon dioxide
Nitric acid
Ammonia
CuSO4
H2S
MgO
CO2
HNO3
NH3
16. A Physical change affects the size, shape or color of a substance but does not affect its chemical
composition. No n _ _
s _ _ _ _ _ _ _ _ is formed. Eg. A change in state in water
to ice or steam. Other examples, cutting, folding a paper, inflating a balloon, red hot filaments
in a toaster, adding sugar to a cup of tea, polishing a surface, lay is molded into a new shape.
17. A Chemical changes (= Chemical reaction) Change that takes place when two or more
substances (reactants) react to form new substances (products).
R
P
18. A typical example of chemical reaction is burning magnesium in air (oxygen).
It can be represented by a WORD EQUATION .
Oxygen
Magnesium
or by a CHEMCIAL EQUATION:
Magnesium oxide
Mg + O2 ------ > MgO
19. Referring to the above Chemical reaction, answer the following questions:
a) Which are the reactants:
__________________________________
b) Which is the product: _________________________
c) What is required in this reaction other than the reactants? ____________
d) Give 2 evidences of chemical changes:
(1) ___________________________________________________________________
(2) ___________________________________________________________________
20. There are 5 evidences of chemical reactions:
(1) A change in
(2)
c _ _ _ _ _.
H _ _ _ may be given out as you can feel the warmth of the test tube.
(3) A
p__________
(4) Fizzing or bubbling implies a
(5) S
is formed
g__
is formed.
_ _ _ _ or light may be given out.
21. There are 3 common gases formed in the laboratory: Oxygen, Carbon dioxide and Hydrogen.
They are all colourless and odourless.
Gas
How to test it?
Hydrogen
Using a Burning splint
Carbon dioxide
Using a Burning splint
Using clear Limewater
Oxygen
Using a Glowing splint
Result
22. Chemical reactions of Acids:
(1) Acid + Metal ----- > Hydrogen (pop sound with burning splint)
Hydrochloric acid + Magnesium --------> Magnesium chloride + Hydrogen
HCl
+ Mg
--------->
MgCl2
+
H2
(2) Acid + Carbonate ----- > Carbon dioxide (turning limewater milky)
Hydrochloric acid + Calcium carbonate ------> Carbon dioxide + Water + Calcium chloride
HCl
+
CaCO3 -----------> CO2 +
H2 O +
CaCl2
23. A catalyst is a substance that alters the rate of a chemical reaction without being used up or
permanently changed chemically
Eg. In the presence of Manganese dioxide (a black powder), hydrogen peroxide will
decompose very rapidly into water and oxygen.
Hydrogen Peroxide ---------------------------->
Water + Oxygen
Manganese dioxide
H2O2
---------------->
H 2O
+ O2
NB: Without Manganese dioxide, this decomposition reaction will take place very very slowly.
The Manganese dioxide is not involved in the formation of new substances.