Question 1

Which of the following best explains why sweating cools the human body during exercise?

Accepted Answer

Sweat absorbs heat from the body as it evaporates, lowering the average kinetic energy of skin molecules.

Question 2

Which phase change requires the greatest input of energy per gram for water?

Accepted Answer

Vaporizing liquid water to steam

Question 3

A pressure cooker allows food to cook faster because:

Accepted Answer

The increased pressure raises the boiling point of water, allowing food to cook at a higher temperature.

Question 4

Which of the following best describes the process of condensation?

Accepted Answer

Gas molecules lose kinetic energy and become part of a liquid, releasing energy.

Question 5

Why does a steam burn cause more damage than a burn from boiling water at the same temperature?

Accepted Answer

Condensing steam releases additional energy as it changes phase to liquid on the skin.

Question 6

Which of the following equations correctly represents the energy required to melt a mass $$m of $$ice at $$0^\circ C$$?

Accepted Answer

$$Q = m L_f$$

Question 7

A can of soda is wet on the outside after being taken from the fridge into warm air. This is because:

Accepted Answer

Water vapor in the air condenses on the cold surface of the can.

Question 8

Which process is responsible for the formation of frost on a cold window during winter?

Accepted Answer

Deposition (gas to solid)

Question 9

If you want to cool a beverage quickly in a picnic cooler, why is it important that the ice melts?

Accepted Answer

Melting ice absorbs a large amount of energy (latent heat of fusion) from the beverage.

Question 10

Which of the following statements about boiling is correct?

Accepted Answer

Boiling point decreases as atmospheric pressure decreases.

Question 11

Which of the following best explains why fog forms when warm, moist air rises and cools?

Accepted Answer

Cooling causes water vapor molecules to slow down and condense into tiny droplets.

Question 12

Which equation gives the energy required to vaporize $$m$$ grams of water at $$100^\circ C$$?

Accepted Answer

$$Q = m L_v$$

Question 13

A block of ice at $$0^\circ C is $$placed in a room at $$25^\circ C. $$Which of the following occurs first?

Accepted Answer

The ice absorbs energy and begins to melt.

Question 14

Which of the following is an example of sublimation?

Accepted Answer

Dry ice (solid CO$$_2) $$turning directly into gas.

Question 15

When snow forms in clouds, what happens to the surrounding air?

Accepted Answer

It is warmed because energy is released during the phase change from gas to solid.

Question 16

Which process is responsible for the cooling effect observed when alcohol evaporates from your skin?

Accepted Answer

Evaporation, which removes energy from your skin as molecules escape.

Question 17

Which of the following best describes the energy changes during the melting of ice?

Accepted Answer

Energy is absorbed by the ice, breaking molecular bonds and increasing molecular motion.

Question 18

Which of the following is true about the boiling of water at high altitudes?

Accepted Answer

Water boils at a lower temperature due to decreased atmospheric pressure.

Question 19

Which of the following processes is a warming process for the environment?

Accepted Answer

Condensation of water vapor

Question 20

Which of the following best explains why you feel cold when stepping out of a hot shower into dry air?

Accepted Answer

Evaporation of water from your skin absorbs heat, lowering your skin temperature.

Change of Phase: Physics with Calculus Study Notes

Study Guide - Practice Questions