Fig. 1 shows a particle model for a substance kept in a sealed box at room temperature. The particles are close together but are not in a fixed pattern. © E...
Question 1 Report
Fig. 1 shows a particle model for a substance kept in a sealed box at room temperature. The particles are close together but are not in a fixed pattern.
(a) Name the state shown in Fig. 1. [1]
(b) Give one property of this state that makes it useful for transporting a solution in a bottle. [1]
(c) Suggest why the substance can change shape when the box is tilted. [2]
A laboratory compares two liquids used for cleaning glass. Table 1 gives their boiling points and observations at 25 degrees C. Both liquids are made of compounds, not elements.
| Liquid | Boiling point / degrees C | Observation after 10 min in an open dish |
|---|---|---|
| Water | 100 | Very small decrease in volume |
| Propanone | 56 | Large decrease in volume |
(a) Name the liquid that evaporates faster at 25 degrees C. [1]
(b) Give the boiling point of water from Table 1. [1]
(c) Suggest why propanone evaporates more quickly than water. [2]
(d) Use the table to give one safety precaution when using propanone near a heater. [1]
Answer Details
Particle model
(a) The close, randomly arranged particles represent a liquid [1].
(b) A liquid flows, can be poured, and takes the shape of its container, making it suitable for transporting a solution in a bottle [1].
(c) Liquid particles can move or slide past one another [1] because they are not held in fixed positions [1]. This enables the liquid to change shape when tilted.
Evaporation data
(a) Propanone evaporates faster at \(25\degree\text{C}\) [1], as shown by its large decrease in volume.
(b) The boiling point of water is \(100\degree\text{C}\) [1].
(c) Propanone has weaker forces between its particles, shown by its lower boiling point [1]. Therefore, more propanone particles have enough energy to escape from the liquid surface at \(25\degree\text{C}\) [1].
(d) Keep propanone away from the heater, and do not use it near flames, because it evaporates readily [1]. Its vapour can then be present near an ignition source.
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