Chemistry 0620 · IGCSE · Solids, liquids and gases

Solids, liquids and gases — practice question

Z is a covalent substance. In one experiment, a pure solid sample of Z was heated continuously for 11 minutes. The graph indicates how the temperature of the pure Z sample changed during the first 9 minutes.
(a)[1]

What is the melting point of pure Z?

(b)[1]

The pure sample of Z started boiling at 9 minutes. It was then boiled for 2 minutes. Use this information to sketch on the grid how the temperature of the pure Z sample changed between 9 minutes and 11 minutes.

(c)[2]

The pure sample of Z was heated continuously from 2 minutes to 5 minutes. Explain, in terms of attractive forces, why the temperature of the pure Z sample did not rise between 2 minutes and 5 minutes.

(d)[2]

Describe how the motion of particles of pure Z changed from 0 minutes to 2 minutes.

(e)[2]

The experiment was repeated with a solid sample of impure Z. Suggest any differences between the melting point and boiling point of impure Z and those of pure Z. melting point ............ boiling point ............

(f)[2]

A pure sample of Z was cooled from $120^\circ\text{C}$ to $20^\circ\text{C}$. The total time taken was 8 minutes. Starting from point X, sketch on the grid how the temperature of the pure Z sample changed between 0 minutes and 8 minutes.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: $80\ ^\circ\text{C}$

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