Q: Calculate the total energy required to convert 10 grams of ice at $$0\ ^\circ\mathrm{C} to $$steam at $$100\ ^\circ\mathrm{C}. $$Use the following values: heat of fusion for water $$= 334\ \mathrm{J/g}$$, specific heat of water $$= 4.18\ \mathrm{J/(g\cdot ^\circ C)}$$, heat of vaporization $$= 2256\ \mathrm{J/g}.$$

$$\text{Total energy} = 3340\ \mathrm{J} + 4180\ \mathrm{J} + 22560\ \mathrm{J} = 30080\ \mathrm{J}$$

Question 1

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

Accepted Answer

Evaporation of sweat absorbs energy from the skin, lowering body temperature.

Question 2

A pressure cooker allows food to cook faster because:

Accepted Answer

The increased pressure raises the boiling point of water, allowing higher cooking temperatures.

Question 3

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

Accepted Answer

Sublimation of water vapor directly to solid ice.

Question 4

When water boils at high altitude (such as in Denver, CO), which of the following is true?

Accepted Answer

The boiling point is lower than at sea level because atmospheric pressure is lower.

Question 5

Which of the following best describes the energy changes during condensation?

Accepted Answer

Energy is released to the surroundings as molecules slow down and join the liquid.

Question 6

Calculate the total energy required to convert 10 grams of ice at $$0\ ^\circ\mathrm{C} to $$steam at $$100\ ^\circ\mathrm{C}. $$Use the following values: heat of fusion for water $$= 334\ \mathrm{J/g}$$, specific heat of water $$= 4.18\ \mathrm{J/(g\cdot ^\circ C)}$$, heat of vaporization $$= 2256\ \mathrm{J/g}.$$

Accepted Answer

$$	ext{Total energy} = 3340\ \mathrm{J} + 4180\ \mathrm{J} + 22560\ \mathrm{J} = 30080\ \mathrm{J}$$

Question 7

Why does steam at $$100\ ^\circ\mathrm{C}$$ cause more severe burns than liquid water at $$100\ ^\circ\mathrm{C}$$?

Accepted Answer

Steam releases additional energy when it condenses on the skin.

Question 8

Which of the following statements about boiling is correct?

Accepted Answer

Boiling is a cooling process because energy is used to change liquid to vapor.

Question 9

A farmer places tubs of unfrozen water in a cellar to prevent jars of food from freezing overnight. Which concept explains why this works?

Accepted Answer

The water releases energy as it freezes, warming the surrounding air.

Question 10

Which of the following best describes the process of sublimation?

Accepted Answer

A solid changes directly to a gas without becoming a liquid.

Question 11

If you step out of a hot shower and feel cold, but then feel warm again when you step back into the shower area, which process is responsible for the warming?

Accepted Answer

Condensation of water vapor on your skin releases energy.

Question 12

Which of the following phase changes requires the most energy per gram for water?

Accepted Answer

Vaporizing liquid water to steam.

Question 13

During which phase change is energy absorbed by a substance?

Accepted Answer

Melting and evaporation.

Question 14

Which of the following best explains why a cold soda can becomes wet when placed in warm air?

Accepted Answer

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

Question 15

Which of the following is true about the energy changes when snow forms in clouds?

Accepted Answer

Energy is released to the surrounding air, warming it.

Question 16

Which of the following involves the greatest number of calories for 1 gram of water?

Accepted Answer

Condensing $$1\ \mathrm{g} of$$ $$100\ ^\circ\mathrm{C}$$ steam to $$100\ ^\circ\mathrm{C}$$ water.

Question 17

Why is it important that ice melts in a picnic cooler to speed up the cooling of beverage cans?

Accepted Answer

Melting ice absorbs a large amount of energy from the beverages.

Question 18

Which of the following is NOT a correct statement about boiling?

Accepted Answer

Boiling point increases as atmospheric pressure decreases.

Change of Phase: Physics with Calculus Study Notes

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