Q: A scientist measures the temperature of a solution as 60 $$^\circC. $$What is this temperature in Fahrenheit?

$$T_F = \frac{9}{5}T_C + 32 = \frac{9}{5} \times 60 + 32 = 140^\circF$$

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

$$\Delta L = \alpha L_0$ \Delta T = 1.2 \times 10$$^{-5}$$ \times 2.0 \times 100 = 0.0024 m$$

Q: A 200 g sample of water is heated from $$20^\circC to$$ $$80^\circC. $$The specific heat capacity of water is $$4186~\frac{J}{kg\cdot ^\circ C}. $$How much heat is required?

$$Q = cm\Delta T = 4186 \times 0.2 \times 60 = 50,232 J$$

Q: A 100 g sample of ice at $$0^\circC is $$melted to water at $$0^\circC. $$The latent heat of fusion for water is $$334,000~\frac{J}{kg}. $$How much heat is required?

$$Q = mL_F = 0.1 \times 334,000 = 33,400 J$$

Question 1

Which of the following best describes what is measured when you record the temperature of an object?

Accepted Answer

The sum of the molecular kinetic energy (internal energy) of the material.

Question 2

A scientist measures the temperature of a solution as 60 $$^\circC. $$What is this temperature in Fahrenheit?

Accepted Answer

$$T_F = \frac{9}{5}T_C + 32 = \frac{9}{5} 	imes 60 + 32 = 140^\circF$$

Question 3

Which of the following statements about the Kelvin temperature scale is correct?

Accepted Answer

A temperature change of 1 K is equal to a change of 1 $$^\circC.$$

Question 4

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

Accepted Answer

$$\Delta L = \alpha L_0$ \Delta T = 1.2 	imes 10$$^{-5}$$ 	imes 2.0 	imes 100 = 0.0024 m$$

Question 5

If a glass jar and a metal lid are both heated by running hot water over them, why does the lid loosen more than the jar?

Accepted Answer

The metal lid has a higher linear expansion coefficient than the glass jar.

Question 6

Which equation correctly relates the volume expansion coefficient $$\beta to $$the linear expansion coefficient $$\alpha$$ for a solid?

Accepted Answer

$$\beta = 3\alpha$$

Question 7

A 500 g block of ice at $$-10^\circC is $$heated until it becomes water at $$20^\circC. $$Which of the following steps is NOT required to calculate the total heat absorbed?

Accepted Answer

Calculating the heat required to vaporize the water.

Question 8

Which of the following best describes the concept of 'latent heat'?

Accepted Answer

The amount of heat required to change the phase of a substance without changing its temperature.

Question 9

A 200 g sample of water is heated from $$20^\circC to$$ $$80^\circC. $$The specific heat capacity of water is $$4186~\frac{J}{kg\cdot ^\circ C}. $$How much heat is required?

Accepted Answer

$$Q = cm\Delta T = 4186 	imes 0.2 	imes 60 = 50,232 J$$

Question 10

Which of the following is true about the temperature of a substance during a phase change?

Accepted Answer

The temperature remains constant until the phase change is complete.

Question 11

A 100 g sample of ice at $$0^\circC is $$melted to water at $$0^\circC. $$The latent heat of fusion for water is $$334,000~\frac{J}{kg}. $$How much heat is required?

Accepted Answer

$$Q = mL_F = 0.1 	imes 334,000 = 33,400 J$$

Question 12

Which of the following best explains why the Celsius scale is commonly used in science?

Accepted Answer

Its zero point is the freezing point of water, making it convenient for scientific measurements.

Question 13

A steel bridge is 500 m long at $$20^\circC. If $$the temperature rises to $$50^\circC$$, and the linear expansion coefficient for steel is $$1.2 	imes 10$$^{-5}$$~^\circC$^{-1}$$, what is the increase in length?

Accepted Answer

$$\Delta L = \alpha L_0$ \Delta T = 1.2 	imes 10$$^{-5}$$ 	imes 500 	imes 30 = 0.18 m$$

Question 14

Which of the following is the correct conversion from $$25^\circC to $$Kelvin?

Accepted Answer

$$T_K = T_C + 273.15 = 25 + 273.15 = 298.15 K$$

Question 15

Which of the following statements about heat is correct?

Accepted Answer

Heat is the energy that flows from a hotter object to a colder one.

Question 16

A 250 g sample of water at $$100^\circC is $$converted to steam at $$100^\circC. $$The latent heat of vaporization for water is $$2,260,000~\frac{J}{kg}. $$How much heat is required?

Accepted Answer

$$Q = mL_V = 0.25 	imes 2,260,000 = 565,000 J$$

Question 17

Which of the following is the correct relationship for the amount of heat $$Q$$ required to change the temperature of a mass $$m of a $$substance with specific heat $$c by$$ $$\Delta T$$?

Accepted Answer

$$Q = cm\Delta T$$

Question 18

Which of the following best describes the difference between specific heat and latent heat?

Accepted Answer

Specific heat is the energy required to change temperature, while latent heat is the energy required to change phase.

Thermodynamics: Temperature, Thermal Expansion, and Heat- lecture 27

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