States of Matter
5 marks · EasyA student leaves a dish of water on a sunny windowsill. After a day, most of the water is gone.
State the process that has occurred to the water.
Describe the arrangement of water particles in the liquid state.
Explain, using particle theory, how the process in (a) happens.
Name the new arrangement and movement of the water particles after the process has finished.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Evaporation
(b) Particles are mostly touching, randomly arranged, can move around each other.
(c) Some surface particles gain enough energy to overcome the forces of attraction and escape as a gas. This is possible at any temperature.
(d) Particles are far apart, randomly arranged, moving rapidly (gas arrangement and movement).
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Marking points
B1 (a) · 1 mark · Correctly states 'evaporation'.
B1 (b) · 1 mark · States liquid particles are randomly arranged, mostly touching, move around each other.
M1 (c) · 1 mark · Explains particles at surface gain enough energy to escape forces of attraction.
A1 (c) · 1 mark · States this occurs at any temperature and escapes as a gas.
B1 (d) · 1 mark · Names new gas arrangement: far apart, randomly arranged, moving rapidly.
Worked solution
a) Evaporation.
b) The particles in a liquid are randomly arranged, mostly touching, and can move around each other.
c) Particles at the surface gain enough energy from the sun to overcome attractive forces and escape as a gas; this can happen at any temperature.
d) After evaporation, the particles are far apart, randomly arranged, and moving rapidly as a gas.