Vapours
Physics · 50 practice questions
Unsaturated and saturated vapours; relationship between saturated vapour pressure (S.V.P.) and boiling; determination of S.V.P. by barometer tube method; formation of dew, mist, fog, clouds and rain; dew point, humidity and relative humidity; hygrometry using wet and dry bulb hygrometers.
- Distinguish between saturated and unsaturated vapours and relate S.V.P. to boiling point.
- Determine S.V.P. by the barometer tube method.
- Differentiate between dew point, humidity and relative humidity, and estimate atmospheric humidity using wet and dry bulb hygrometers.
Try a few questions
- Practice question 1
High relative humidity conditions can feel more uncomfortable than the actual air temperature suggests mainly because
- A.sweat evaporates much more quickly, over-cooling the body
- B.the air itself becomes significantly colder under high humidity
- C.perspiration stops entirely once humidity exceeds 50%
- D.sweat evaporates more slowly, reducing the body's cooling efficiency
Show the answer
D. sweat evaporates more slowly, reducing the body's cooling efficiency
Humid air can already hold less additional moisture, slowing sweat evaporation and reducing the body's natural cooling.
- Practice question 2
Fog is essentially
- A.a cloud that forms only high in the atmosphere, never near the ground
- B.a cloud that forms at ground level, while typical clouds form higher in the atmosphere
- C.entirely unrelated to cloud formation processes
- D.a phenomenon that only occurs over large bodies of water
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B. a cloud that forms at ground level, while typical clouds form higher in the atmosphere
Fog and clouds share the same basic formation process, differing mainly in their altitude above the ground.
- Practice question 3
Relative humidity is best defined as the
- A.ratio of the actual mass of water vapour in air to the mass needed to saturate it at the same temperature, expressed as a percentage
- B.total mass of water vapour present in the atmosphere, in kilograms
- C.exact temperature of the surrounding air
- D.volume of air present in a given region
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A. ratio of the actual mass of water vapour in air to the mass needed to saturate it at the same temperature, expressed as a percentage
Relative humidity specifically compares actual moisture content to the maximum possible at that same temperature.
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