Question

Which of the following statements is correct?

A)The phase change from liquid to gas is exothermic.
substance with a low boiling point would be expected to have a relatively low vapor pressure at a low temperature.
B) Liquids boil at lower than normal temperatures in Death Valley, since it is below sea level.
C)When a substance condenses, heat energy is given off.
D)The phase change from solid to liquid is exothermic.

Answer 1

When a substance condenses, heat energy is given off.

Option C.

Step-by-step explanation:

When a liquid changes into gas or a solid changes into a liquid, the heat is needed to be supplied from the surrounding. So heat is absorbed in this process, not emitted.

Vapour pressure of a liquid is higher when the tendency of the liquid to boil is higher at a particular temperature. So vapour pressure of a liquid increases with increase in temperature until it boils. So a fluid with low boiling point will have higher vapour pressure st normal temperature, because it's near to its boiling point. So we get so much smell of alcohol when it's kept open.

Death valley is below sea level. So the height of atmosphere over death valley is more than normal places. So atmospheric pressure over death valley is more. So boiling of water or any liquid will take place at higher temperature than its boiling point.

Condensation happens when a substance is cooled. So heat is absorbed by the surrounding.