O-LevelPhysicsThermal Physics5054/21 · Oct/Nov 2015 · Q55 Marks
In a steam cleaner, water is heated to its boiling point and is then turned into steam (water in the gas state).
- (a)Define boiling point.[1]
- (b)(i)Describe the molecular structure of a liquid.[2]
- (b)(ii)Explain, using ideas about molecules, why thermal energy (heat) must be supplied to the water as it boils.[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2015). The mark or mark type is shown in brackets.
- [1] temperature at which a liquid becomes a gas
- [1] molecules close together/touching or closer than in gas
- [1] randomly arranged or irregular structure
- [1] to separate/increase the distance between molecules
- [1] work done against (intermolecular) forces or supply p.e. or break bonds
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