Q: A steel rod of length $$L_0 = 2.0$$\ \text{m}$$ at 20$$\ ^\circ\text{C}$$ is heated to 120$$\ ^\circ\text{C}$$. If the coefficient of linear expansion is $$\alpha = 1.2 \times $$10^{-5}$$\ \text{K}^{-1}$$, what is the change in length $$\Delta L$$?

$$\Delta L = \alpha L_0$ \Delta T = 1.2 \times 10$$^{-5}$$ \times 2.0 \times (120-20) = 0.0024\ \text{m}$$

Q: A 50.0 g block of ice at $$0\ ^\circ\text{C} is $$placed in 100 g of water at $$20\ ^\circ\text{C}. If $$the latent heat of fusion for ice is $$L = 334\ \text{J/g}$$ and the specific heat of water is $$c = 4.18\ \text{J/g}\cdot\text{K}$$, how much heat is required to melt the ice completely?

$$Q = mL = 50.0 \times 334 = 16,700\ \text{J}$$

Q: Which of the following best explains why lakes freeze from the top down?

Water is most dense at $$4\ ^\circ\text{C}$$, so colder water stays on top and freezes first.

Question 1

Which statement best describes the Zeroth Law of Thermodynamics?

Accepted Answer

If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other.

Question 2

A steel rod of length $$L_0 = 2.0$$\ 	ext{m}$$ at 20$$\ ^\circ	ext{C}$$ is heated to 120$$\ ^\circ	ext{C}$$. If the coefficient of linear expansion is $$\alpha = 1.2 	imes $$10^{-5}$$\ 	ext{K}^{-1}$$, what is the change in length $$\Delta L$$?

Accepted Answer

$$\Delta L = \alpha L_0$ \Delta T = 1.2 	imes 10$$^{-5}$$ 	imes 2.0 	imes (120-20) = 0.0024\ 	ext{m}$$

Question 3

Which of the following is true about the Kelvin temperature scale?

Accepted Answer

Kelvin temperatures are measured in kelvins, not degrees kelvin.

Question 4

A glass plate with a circular hole is heated. What happens to the diameter of the hole?

Accepted Answer

The diameter increases as the plate expands.

Question 5

Which equation describes the heat required to change the temperature of a mass $$m of $$material by $$\Delta T$$?

Accepted Answer

$$Q = mc\Delta T$$

Question 6

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

Accepted Answer

The temperature remains constant during the phase change.

Question 7

A 50.0 g block of ice at $$0\ ^\circ	ext{C} is $$placed in 100 g of water at $$20\ ^\circ	ext{C}. If $$the latent heat of fusion for ice is $$L = 334\ 	ext{J/g}$$ and the specific heat of water is $$c = 4.18\ 	ext{J/g}\cdot	ext{K}$$, how much heat is required to melt the ice completely?

Accepted Answer

$$Q = mL = 50.0 	imes 334 = 16,700\ 	ext{J}$$

Question 8

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

Accepted Answer

Radiation

Question 9

A rod is prevented from expanding as its temperature increases. What is the resulting physical effect?

Accepted Answer

Thermal stress develops in the rod.

Question 10

Which equation gives the rate of heat transfer by conduction through a rod?

Accepted Answer

$$H = \frac{kA (T_H - T_C)}{L}$$

Question 11

A railroad track is designed with gaps between segments. What is the primary reason for these gaps?

Accepted Answer

To allow for thermal expansion and prevent buckling on hot days.

Question 12

Which equation describes the heat required to change the temperature of $$n$$ moles of a material by $$\Delta T$$?

Accepted Answer

$$Q = nC\Delta T$$

Question 13

Which of the following best explains why lakes freeze from the top down?

Accepted Answer

Water is most dense at $$4\ ^\circ	ext{C}$$, so colder water stays on top and freezes first.

Question 14

A person steps out of a swimming pool and feels cold. Which process is responsible for this sensation?

Accepted Answer

Evaporation removes heat of vaporization from the body.

Question 15

Which equation describes the heat transfer during a phase change?

Accepted Answer

$$Q = mL$$

Question 16

Which equation describes the rate of heat transfer by radiation from a surface?

Accepted Answer

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

Question 17

A surveyor uses a steel measuring tape calibrated at $$20\ ^\circ	ext{C} to $$measure a distance at $$35\ ^\circ	ext{C}. If $$the tape reads $$35.794\ 	ext{m}$$, what is the actual distance measured?

Accepted Answer

The actual distance is greater than $$35.794\ 	ext{m}$$ because the tape expands with temperature.

Question 18

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

Accepted Answer

Warm air rising above a heating element in a room.

Question 19

Which property of water is responsible for its anomalous expansion between $$0\ ^\circ	ext{C}$$ and $$4\ ^\circ	ext{C}$$?

Accepted Answer

Water decreases in volume with increasing temperature in this range.

Chapter 17: Temperature and Heat – Study Notes

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