Q: A 2 kg block of copper ($$c = 0.385 J/g K) is $$heated from $$20^ ext{\circ}C to$$ $$80^ ext{\circ}C. $$How much energy is required? (Assume $$c is $$per gram.)

$$Q = 2000 \times 0.385 \times 60 = 46,200 J$$

Q: A 0.5 kg sample of ice at $$0^ ext{\circ}C is $$melted by adding heat. How much energy is required if the latent heat of fusion for ice is $$L_f = 334 kJ/kg$$?

$$Q = 0.5 \times 334,000 = 167,000 J$$

Question 1

Which of the following best describes the First Law of Thermodynamics?

Accepted Answer

The change in internal energy of a system equals the heat added to the system minus the work done by the system: $$\Delta U = Q - W$$

Question 2

A 2 kg block of copper ($$c = 0.385 J/g K) is $$heated from $$20^	ext{\circ}C to$$ $$80^	ext{\circ}C. $$How much energy is required? (Assume $$c is $$per gram.)

Accepted Answer

$$Q = 2000 	imes 0.385 	imes 60 = 46,200 J$$

Question 3

Which process involves no heat transfer ($$Q = 0) $$between a system and its surroundings?

Accepted Answer

Adiabatic

Question 4

During an isothermal expansion of an ideal gas, which statement is true?

Accepted Answer

The temperature remains constant and $$Q = W.$$

Question 5

A calorimetry experiment mixes 100 g of water at $$80^	ext{\circ}C $$with 100 g of water at $$20^	ext{\circ}C in an $$isolated system. What is the final temperature?

Accepted Answer

$$T_f = 50^	ext{\circ}C$$

Question 6

Which equation best represents the heat conducted through a wall of thickness $$d$$, area $$A$$, and thermal conductivity $$k$$, with temperature difference $$\Delta T$$?

Accepted Answer

$$Q = k \frac{A \Delta T}{d}$$

Question 7

Which of the following statements about specific heat is correct?

Accepted Answer

Specific heat is the amount of energy needed to raise 1 kg of a substance by 1 K.

Question 8

Why do metals generally feel colder than wood at the same temperature?

Accepted Answer

Metals have a higher thermal conductivity than wood.

Question 9

A gas undergoes an adiabatic compression. Which of the following occurs?

Accepted Answer

The internal energy of the gas increases.

Question 10

Which of the following is NOT a method of heat transfer discussed in the materials?

Accepted Answer

Reflection

Question 11

A 0.5 kg sample of ice at $$0^	ext{\circ}C is $$melted by adding heat. How much energy is required if the latent heat of fusion for ice is $$L_f = 334 kJ/kg$$?

Accepted Answer

$$Q = 0.5 	imes 334,000 = 167,000 J$$

Question 12

Which statement about molar specific heat is correct?

Accepted Answer

Molar specific heat is the energy needed to raise 1 mole of a substance by 1 K.

Question 13

In a real-world scenario, why does a metal spoon heat up quickly when placed in hot soup compared to a plastic spoon?

Accepted Answer

Metal has a higher thermal conductivity than plastic.

Question 14

Which of the following best describes convection?

Accepted Answer

Heat transfer by movement of fluid.

Question 15

A gas is compressed in a cylinder, and no heat is exchanged with the surroundings. Which equation describes the change in internal energy?

Accepted Answer

$$\Delta U = -W$$

Question 16

Which factor does NOT affect the rate of heat conduction through a material?

Accepted Answer

Color

Question 17

A 1 kg block of aluminum ($$c = 900 J/kg K) at$$ $$100^	ext{\circ}C is $$placed in 2 kg of water ($$c = 4186 J/kg K) at$$ $$20^	ext{\circ}C. $$What is the final equilibrium temperature? (Assume no heat loss to surroundings.)

Accepted Answer

$$T_f \approx 40^	ext{\circ}C$$

Question 18

Which of the following is true about heat transfer by radiation?

Accepted Answer

It can occur in a vacuum.

Question 19

Which scenario best illustrates an adiabatic process in real life?

Accepted Answer

Rapid compression of air in a bicycle pump.

Work, Heat, and the First Law of Thermodynamics: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard