Q: A 2.0 kg block of aluminum (specific heat $$c = 900 \ \mathrm{J/(kg \cdot K)}) is $$heated from $$20^\circC to$$ $$50^\circC. $$How much heat is required?

$$Q = 2.0 \times 900 \times (50 - 20) = 54,000 \ \mathrm{J}$$

Q: A 0.5 kg block of ice at $$0^\circC is $$placed in contact with 1.0 kg of water at $$20^\circC. $$The latent heat of fusion for ice is $$3.34 \times 10^5$ \ \mathrm{J/kg}$$ and the specific heat of water is $$4.18 \times 10^3$ \ \mathrm{J/(kg \cdot K)}. $$What is the minimum amount of heat required to melt all the ice?

$$Q = 0.5 \times 3.34 \times 10^5$ = 1.67 \times 10^5$ \ \mathrm{J}$$

Question 1

Which of the following statements best describes thermal equilibrium?

Accepted Answer

Two objects are in thermal equilibrium if they have the same temperature and no net heat flows between them.

Question 2

The Zeroth Law of Thermodynamics is essential for which practical application?

Accepted Answer

Establishing the basis for temperature measurement using thermometers.

Question 3

A steel bridge is constructed with expansion joints. What is the primary reason for including these joints?

Accepted Answer

To prevent the bridge from expanding and buckling during hot weather.

Question 4

Which equation correctly relates the change in length $$\Delta L of a $$rod to its original length $$L_0$$, the coefficient of linear expansion $$\alpha$$, and the temperature change $$\Delta T$$?

Accepted Answer

$$\Delta L = \alpha L_0$ \Delta T$$

Question 5

A glass beaker with a hole in the center is heated. What happens to the diameter of the hole?

Accepted Answer

The diameter of the hole increases.

Question 6

Which of the following best explains why lakes freeze from the top down rather than from the bottom up?

Accepted Answer

Water has a maximum density at $$4^\circC$$, causing colder water to float.

Question 7

A 2.0 kg block of aluminum (specific heat $$c = 900 \ \mathrm{J/(kg \cdot K)}) is $$heated from $$20^\circC to$$ $$50^\circC. $$How much heat is required?

Accepted Answer

$$Q = 2.0 	imes 900 	imes (50 - 20) = 54,000 \ \mathrm{J}$$

Question 8

Which equation gives the amount of heat $$Q$$ required to change the temperature of $$n$$ moles of a substance with molar heat capacity $$C by$$ $$\Delta T$$?

Accepted Answer

$$Q = nC\Delta T$$

Question 9

During a phase change, such as melting or boiling, what happens to the temperature of a substance as heat is added?

Accepted Answer

The temperature remains constant.

Question 10

Which formula correctly expresses the heat $$Q$$ required for a phase change involving a mass $$m$$ and latent heat $$L$$?

Accepted Answer

$$Q = mL$$

Question 11

A 0.5 kg block of ice at $$0^\circC is $$placed in contact with 1.0 kg of water at $$20^\circC. $$The latent heat of fusion for ice is $$3.34 	imes 10^5$ \ \mathrm{J/kg}$$ and the specific heat of water is $$4.18 	imes 10^3$ \ \mathrm{J/(kg \cdot K)}. $$What is the minimum amount of heat required to melt all the ice?

Accepted Answer

$$Q = 0.5 	imes 3.34 	imes 10^5$ = 1.67 	imes 10^5$ \ \mathrm{J}$$

Question 12

Which of the following is the correct equation for the rate of heat transfer $$H by $$conduction through a rod of length $$L$$, cross-sectional area $$A$$, and thermal conductivity $$k$$, with a temperature difference $$T_H - T_C$$ across its ends?

Accepted Answer

$$H = kA \dfrac{T_H - T_C}{L}$$

Question 13

Which mechanism of heat transfer does NOT require matter to be present between two objects?

Accepted Answer

Radiation

Question 14

A blackbody emits thermal radiation according to the Stefan-Boltzmann law. Which equation gives the power $$H$$ radiated from a surface of area $$A$$ and emissivity $$e at $$absolute temperature $$T$$?

Accepted Answer

$$H = e \sigma A T^4$

Question 15

A steel rod is fixed at both ends and its temperature is increased. What is the resulting effect?

Accepted Answer

Thermal stress develops in the rod.

Question 16

Which of the following best describes the specific heat of a substance?

Accepted Answer

The amount of heat required to raise the temperature of 1 kg of the substance by 1 K.

Question 17

A 1.0 kg block of copper and a 1.0 kg block of aluminum are both heated by 1000 J. If the specific heat of copper is less than that of aluminum, which block experiences the greater temperature increase?

Accepted Answer

The copper block.

Question 18

Which of the following is a real-world example of convection?

Accepted Answer

Warm air rising above a radiator in a room.

Question 19

Why do people feel cold when stepping out of a swimming pool on a warm, windy day?

Accepted Answer

The latent heat of vaporization is absorbed from their skin as water evaporates.

Chapter 17: Temperature and Heat – Structured Study Notes

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