Secondary 1 Science
Compounds and Mixtures
Name: ________________________(
)
Date: ___________
Class: ___________
Section A : Fill in the blanks below.
A.
Compounds
1.
A compound is a subtance which is made up of two or more different elements
chemically combined. Water, carbon dioxide, sugar and common salt are all
examples of compounds.
Compound
Elements in the
compound
Water
Hydrogen and oxygen
Carbon dioxide
Carbon and oxygen
Common salt (Sodium
Sodium and chlorine
chloride)
2.
Copper(II) Carbonate
Copper, carbon and oxygen
Magnesium oxide
Magnesium and oxygen
Ammonium chloride
Nitrogen, hydrogen, chlorine
Characteristics of compounds:

A chemical change takes place when a compound is formed. Heat and/or
light may be released or absorbed.

The properties of the compound are different from the constituent elements,
i.e. the elements which make the compound.

Elements in a compound are combined in a fixed proportion by mass.

A compound can be broken down into simpler substances by chemical
methods. These methods include heating, exposure to light and effect of
electricity.
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B.
Mixtures
1.
A mixture consists of two or more substances, which are not chemically combined.
Sugar solution, salt solution, soil, air, aerated water, blood are examples of mixtures.
2.
Characteristics of mixtures:

When a mixture is formed, no chemical reaction occurs. Hence, there is little
or no light or heat taken in or given out.

A mixture has the properties of the substances of which it is made.

A mixture can be separated easily by physical methods, for example,
filtration, distillation, evaporation.

C.
The components in a mixture are not mixed in any fixed proportion.
Word Equation ( This section will be discussed further in class)
1.
Word equations represent chemical reactions which take place.
2.
Word equation can tell us what substances are reactants or the starting
materials, and what substances are product(s).
3.
Products are new substances obtained from the reaction.
Section B : Answer the following questions in the space provided.
1.
Explain why water is a compound.
Water is made up of oxygen and hydrogen. Oxygen is a colourless gas which
supports combustion while hydrogen is a gas which burns with a pale blue flame.
Water is a liquid at room temperature and does not have the properties of its
constituents elements.
Also, water contains hydrogen and oxygen, combined in a fixed proportion. For
example,
1 g of hydrogen gas + 8 g of oxygen  9 g of water.
Lastly, water can only be broken down by chemical means, i.e. electrolysis (passing
through electricity).
Created by Mrs ChuWL
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2.
Explain why air is a mixture.

Air can be made by simply mixing its component gases, nitrogen, oxygen,
carbon dioxide, noble gases and water vapour.

Air has properties of its constituents, nitrogen, oxygen, carbon dioxide, water
vapour and noble gases. Air support combustion because the oxygen gas in
it supports combustion.

Air can be separated into its components by fractional distillation. We can
obtain nitrogen, and oxygen separately by physical means.

The constituents gases in air may be mixed in different proportions, This may
vary with place and time. For example, we can find a higher proportion of
carbon dioxide in the city than at the seaside (why?)
3.
Distinguish between elements, compounds and mixtures.
Element
Compound
Mixture
An element is made up of
Different elements in a
The components in
only one kind of atom.
compound combine in a
mixtures are not mixed in
fixed proportion by mass.
any fixed proportion.
An element is the simplest A chemical change takes
No chemical reaction
pure substances
place when a compound
occurs. There is little or
is formed.
no heat and/or light taken
in or given out.
An element has properties A compound has
A mixture has the
similar to those of their
properties which are
properties of the
atoms.
different from the
substances of which it is
properties of its
made.
constituent elements.
Elements cannot be
A compound can only be
A mixture can be
broken down whether by
broken down, by chemical
separated easily by
physical or chemical
methods, for example
physical methods, for
means.
heating (decomposition)
example, filtration,
or by passing electricity
distillation, evaporation.
through it.
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4.
Complete the following word equation:
a.
Oxygen + Hydrogen  water
b.
Carbon + Oxygen (in excess)  Carbon dioxide
c.
Magnesium + oxygen  Magnesium oxide
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