Change of State
Physics · 50 practice questions
Latent heat; specific latent heats of fusion and vaporization; melting, evaporation and boiling; influence of pressure and dissolved substances on boiling and melting points; applications in appliances.
- Differentiate between latent heat and specific latent heats of fusion and vaporization.
- Differentiate between melting, evaporation and boiling.
- Examine the effects of pressure and dissolved substances on boiling and melting points, and solve numerical problems.
Try a few questions
- Practice question 1
Condensation, the reverse process of evaporation or boiling, is when a gas changes into a liquid,
- A.absorbing latent heat in the process
- B.releasing latent heat in the process
- C.with no exchange of latent heat at all
- D.while its temperature continues to rise throughout the process
Show the answer
B. releasing latent heat in the process
Since vaporization absorbs latent heat, its reverse (condensation) correspondingly releases that same latent heat.
- Practice question 2
Sublimation is the direct change of state from solid to gas (or gas to solid), without passing through the liquid state, as seen in substances like
- A.solid carbon(IV) oxide (dry ice) and iodine
- B.water and ethanol
- C.iron and copper
- D.oxygen and nitrogen gas
Show the answer
A. solid carbon(IV) oxide (dry ice) and iodine
These are classic examples of substances that sublime directly, without an intermediate liquid phase, under normal conditions.
- Practice question 3
A substance's boiling point decreases at higher altitudes mainly because
- A.atmospheric pressure is higher there, requiring a higher vapour pressure to boil
- B.the surrounding air is always colder at higher altitudes
- C.gravity has no effect at all on boiling point at any altitude
- D.atmospheric pressure is lower there, so a lower vapour pressure is sufficient for boiling
Show the answer
D. atmospheric pressure is lower there, so a lower vapour pressure is sufficient for boiling
Lower atmospheric pressure at altitude means the liquid's vapour pressure reaches equality with it at a lower temperature.
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