9.3 Alloys

Physical properties of pure metals
■ Pure metal

	►	Soft and not very strong.
	►	Atoms of the same size arranged in a regular organised close packing arrangement.

■ Physical properties of pure metals:

	►	Ductile ○ Pure metals are soft and ductile because the layers of atoms can slide over each other easily when an external force is applied on them.
	►	Malleable ○ Most natural arrangement of atoms in pure metals are not perfect and may contain empty spaces in the structures. ○ When hammered or pressed, groups of metal atoms may glide into new position in these empty spaces. This makes metals malleable.

■ High melting and boiling point

►

Strong forces of attraction between metal atoms require high energy to overcome. Thus, most metals have high melting and boiling points.

Alloy
■ Alloy

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Mixture of a pure metal with small quantities of other metals.

■ Arrangement of atom in an alloy

	►	In alloying process, a foreign metal is added to the molten pure metal.
	►	The foreign atoms filling up the spaces between the atoms of the pure metal.
	►	These foreign metal atoms disrupt the orderly arrangement of the metal atoms.
	►	Thus the layers of metal atoms are prevented from sliding over each other easily.
	►	This makes the metal harder, less malleable and less ductile.

Laboratory Activity 9.3.1 : Investigating the difference in hardness of an alloy and a pure metal

Purpose of making alloys
■ Purpose of making alloys

	►	Increase the hardness of metals.
	►	Prevent the corrosion of metals.
	►	Improve beauty and lustre of metals.

■ Uses of alloys

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The animation below shows the composition, properties and uses of some common alloys.

← 9.2 Manufacture of Ammonia and its Salt

9.4 Synthetic Polymers and Their Uses →

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