The arrangement of the particles
4 marks · NormalA student compares the density and shape of three unknown substances at room temperature. The data are in the table below.
| Substance | Density (g/cm^3) | Shape |
|---|---|---|
| A | 1.0 | Fixed |
| B | 0.0013 | No fixed shape |
| C | 0.79 | No fixed shape |
Which substance is most likely to be a liquid at room temperature? Give one reason for your answer.
Using the particle model, explain why substance B can easily be compressed.
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.
Show answer
(a) C is most likely a liquid because it has no fixed shape and a density much higher than that of a gas but lower than a solid.
(b) In gases (like substance B), particles are far apart so they can be pushed closer together easily; lots of empty space allows compression.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Identifies C as the liquid.
B2 (a) · 1 mark · Explains it is a liquid because it has no fixed shape and moderate density.
B3 (b) · 1 mark · Explains that in a gas, particles are far apart.
B4 (b) · 1 mark · States that these large spaces allow compression (particles can be pushed closer together).
Worked solution
a) C is most likely to be a liquid because it does not have a fixed shape and its density (0.79 g/cm^3) is much higher than that of a gas, but less than most solids. b) In a gas (such as B), the particles are far apart with a lot of empty space between them. This space allows the particles to be pushed closer together, so the substance can be compressed easily.