IGCSE Chemistry Paper-1: Specimen Questions with Answers 20 - 21 of 99

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Question 20

Question

MCQ▾

Aluminum is an important metal with many uses. Its properties are:

1 It is a good conductor of heat.

2 It has a low density.

3 It has an oxide layer that prevents corrosion.

What explains the use of aluminum for cooking and storing food?

Choices

Choice (4)

a.

1 and 2 only

b.

1,2 and 3

c.

2 and 3 only

d.

1 only

Answer

b.

Explanation

Aluminum is now the second most widely used metal in the world. The above properties can be explained as:

  • Aluminum is an excellent conductor of heat and electricity. An aluminum conductor weighs approximately half as much as a copper conductor having the same conductivity.
  • With a density one third that of steel, 2.700 . The low density of aluminum accounts for it being lightweight but this does not affect its strength.
  • Aluminum reacts with the oxygen in the air to form an extremely thin layer of oxide. This layer is dense and provides excellent corrosion protection. The layer is self-repairing if damaged.

Therefore all the above three properties are useful.

Question 21

Question

MCQ▾

The diagrams show the arrangement of particles in three different physical states of substance X.

Find the Correct State of Matter

Which statement about the physical states of substance X is correct?

Choices

Choice (4)

a.

State 2 changes directly to state 3 by condensation.

b.

State 1 changes to state 2 by diffusion.

c.

The substance in state 3 has a fixed volume.

d.

Particles in state 1 vibrate about fixed positions.

Answer

c.

Explanation

The molecules in a solid are in fixed positions and are close together. Although the molecules can still vibrate, they cannot move from one part of the solid to another part. As a result, a solid does not easily change its shape or its volume.

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