Question 1

Which of the following statements best describes what happens to temperature and energy during a phase change on a heating curve?

Accepted Answer

Temperature remains constant while potential energy increases.

Question 2

Given the specific heat of ice is $$2.09 \ \frac{J}{g \ ^\circ C}$$, how much energy (in J) is required to raise the temperature of 10.0 g of ice from $$-10.0 \ ^\circ C to$$ $$0.0 \ ^\circ C$$?

Accepted Answer

$$209 \ J$$

Question 3

A sample of water at $$100 \ ^\circ C is $$converted to steam at $$100 \ ^\circ C. $$Which of the following best describes the energy change?

Accepted Answer

Energy is absorbed as heat is transformed into potential energy.

Question 4

If $$5.32 \ kJ of $$heat are added to a $$15.5 \ g$$ ice cube at $$-5.00 \ ^\circ C$$, what is the first step in determining the final state and temperature?

Accepted Answer

Calculate the energy needed to raise the ice to $$0.00 \ ^\circ C$$ using $$q = m c \Delta T.$$

Question 5

Which equation would you use to calculate the energy required to melt a solid at its melting point?

Accepted Answer

$$q = m \Delta H_{fus}$$

Question 6

A $$76.4 \ g$$ sample of acetone (molar mass $$58.08 \ g/mol) is $$cooled from $$-30 \ ^\circ C ($$liquid) to $$-115 \ ^\circ C ($$solid). Which steps must be included in the calculation of total energy released?

Accepted Answer

Cooling the liquid, freezing the liquid, and cooling the solid.

Question 7

During the flat portions of a heating curve, which of the following is true?

Accepted Answer

Temperature remains constant while the substance undergoes a phase change.

Question 8

Which value represents the specific heat of liquid water according to the provided data?

Accepted Answer

$$4.184 \ \frac{J}{g \ ^\circ C}$$

Question 9

If $$334 \ J/g is $$the heat of fusion for water, how much energy is required to melt $$20.0 \ g of $$ice at $$0 \ ^\circ C$$?

Accepted Answer

$$6,680 \ J$$

Question 10

A $$15.5 \ g$$ ice cube at $$-5.0 \ ^\circ C is $$heated with $$5.32 \ kJ of $$energy. After the ice reaches $$0.0 \ ^\circ C$$, how much energy is required to completely melt it? (Use $$\Delta H_{fus} = 334 \ J/g)$$

Accepted Answer

$$5,177 \ J$$

Question 11

Which of the following best explains why temperature does not change during a phase change?

Accepted Answer

The energy added is used to break intermolecular forces rather than increase kinetic energy.

Question 12

Which process requires the most energy per gram for water?

Accepted Answer

Vaporization ($$\Delta H_{vap} = 2,260 \ J/g)$$

Question 13

A $$50.0 \ g$$ sample of water at $$25.0 \ ^\circ C is $$heated to $$75.0 \ ^\circ C. $$How much energy is required? (Use $$c = 4.184 \ J/g \ ^\circ C)$$

Accepted Answer

$$10,460 \ J$$

Question 14

Which of the following is true about the average kinetic energy during a phase change?

Accepted Answer

It remains constant.

Question 15

If $$1.67 \ J/g \ ^\circ C is $$the specific heat of liquid acetone, how much energy is needed to heat $$76.4 \ g of $$acetone from $$-115 \ ^\circ C to$$ $$-30 \ ^\circ C$$?

Accepted Answer

$$10,800 \ J$$

Question 16

Which of the following steps is NOT required when calculating the energy needed to convert ice at $$-10 \ ^\circ C to $$steam at $$110 \ ^\circ C$$?

Accepted Answer

Calculating the energy to cool steam from $$110 \ ^\circ C to$$ $$100 \ ^\circ C.$$

Question 17

Which formula would you use to calculate the energy required to heat $$m$$ grams of a substance by $$\Delta T$$ degrees Celsius?

Accepted Answer

$$q = m c \Delta T$$

Question 18

A $$20.0 \ g$$ sample of steam at $$100 \ ^\circ C is $$condensed to liquid water at $$100 \ ^\circ C. $$How much energy is released? ($$\Delta H_{vap} = 2,260 \ J/g)$$

Accepted Answer

$$45,200 \ J$$

Question 19

Which of the following best describes the difference between heating and cooling curves?

Accepted Answer

Heating curves show energy absorption, while cooling curves show energy release.

Heating and Cooling Curves: Phase Changes and Energy Calculations

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