F'3 Chemistry Revision Short Questions Part I

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F.3 Chemistry RevisionShort Questions (Part I)
1. What is Chemistry? (2 marks)
Chemistry is the science of substances.
2. What are physical properties? (2 marks)
Physical properties are properties that do not
change after the observation.
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3. What are chemical properties (2 marks)
Chemical properties are properties that can only
be observed during a change.
4. What are the THREE characteristics of a
chemical change? (3 marks)

• There is a change in the nature of the substance.
• The change is irreversible.
• A new substance is (new substances are) formed.

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5. What are the THREE characteristics of a
physical change?
(i) Cause no change in the nature of the
substance. (ii) The change is reversible. (iii)
There is no new substance formed.
6. Give THREE good reasons to study
chemistry. Students own answers.
7. What is a pure substance?
A pure substance contains only one kind of matter.
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8. What is a mixture? (3 marks)
A mixture contains more than one pure substance
mixed together.
9. What is the main purpose of filtration? (3
marks)
Filtration is used to separate an insoluble
substance from a liquid or a solution.
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10. What is the main purpose of crystallization?
(3 marks)
It is used to obtain a pure substance when a hot
solution cools to a low temperature, when the
impurities are automatically excluded.
11. What is the main purpose of evaporation? (3
marks)
It is used to remove water from a dissolved solid.
12. Name a method to obtain pure water from a
mixture of salt and water. (1 mark)
This can be done by distillation.
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13. (a) Name a method to turn a mixture of
ethanol and water stronger in
ethanol content. (1 mark)
This can be done by fractional
distillation.
(b) Name the plant where wine is produced. (1
mark)
It is called a brewery.
14. What is the main difference between
distillation and fractional distillation?
(2 marks)
Fractional distillation consists of a series of
repeated distillations.
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15. A mixture of salt, iron powder and sand is
given. Describe a simple procedure
(paying attention to name all the
separation methods) to obtain the salt, the iron
powder and sand as pure substances. (6
marks)
Use a magnet to attract and remove all the iron
powder. Dissolve the remaining salt and sand
mixture in water and stir. Filter to obtain sand
as residue. Evaporate the salt mixture to obtain
salt as residue.
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16. What is an element? Give the names of TWO
elements. (3 marks)
An element is a substance that cannot be further
broken down to two or more simpler substances by
chemical methods. e.g. sodium, oxygen, carbon,
hydrogen, etc. (any TWO)
17. What is a compound? Is air a compound?
Explain. (5 marks)
A compound is a pure substance made up of two or
more elements chemically combined together.
Air is a mixture of compounds and elements and so
it is not a compound.
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18. State TWO distinctive properties of metals.
(2 marks)

• Metals are shiny when freshly cut.
• Metals are good conductors of heat and
  electricity.
• Metals are ductile and malleable.
• Metals have relatively high melting and boiling
  points.
• (any two)

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19. State THREE distinctive properties of
non-metals. (3 marks)

• Non-metals are dull in appearance.
• Non-metals are brittle.
• Non-metals are poor conductors of heat and
  electricity.
• Non-metals have relatively low melting and
  boiling points.
• (any three)

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20. Use iron, sulphur and iron sulphide as
examples, state TWO differences between
iron sulphide and the elements that form
the compound. (2 marks)

• Iron is magnetic while iron sulphide is
  non-magnetic.
• When dilute acid is added to sulphur there is no
  observation. However when dilute acid is added
  to iron sulphide a gas with rotten egg smell is
  given off.

21. What is an atom? (3 marks)
An atom is the smallest particle of an element
that can still have the properties of that
element.
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22. Name the THREE sub-atomic particles inside an
atom. (3 marks)
proton, neutron and electron
23. What is the atomic number of an element? (2
marks)
The atomic number of an element is the number of
protons in an atom of the element.
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24. What is the mass number of an atom? (3 marks)
The mass number of an atom is the sum of the
number of protons and the number of neutrons in
the atom .
25. Two species with the following notations are
shown Do they belong to a pair
of isotopes? Explain your answer. (3
marks)
and
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They are isotopes as they have the same chemical
symbol (Cl) and atomic number (17). The istopes
have different mass number (37 and 35), though.
26. What is the carbon-12 scale? (3 marks)
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27. What it the relative atomic mass of an
element? (3 marks)
The relative atomic mass of an element is the
average mass of all the naturally occurring
isotopes on the carbon-12 scale.
28. State the building up principle regarding
electronic configuration of atoms. (3
marks)
electrons must first be filled into the shells of
lowest energy before the shells of higher energy
are filled.