Q: A student catches the flu and his body temperature increases from $37.0^\circ$C to $39.0^\circ$C. If his mass is $70$ kg and the specific heat of the body is $3400$ J/kg K, how much energy is required for this temperature increase?

$Q = (70)(3400)(2.0) = 4.8 \times 10^5$ J

Question 1

Which of the following best describes the first law of thermodynamics?

Accepted Answer

Energy cannot be created or destroyed, only transferred as work or heat.

Question 2

A gas in a well-insulated cylinder is compressed by a steady force. What happens to the temperature of the gas?

Accepted Answer

It increases.

Question 3

Which equation correctly expresses the first law of thermodynamics for a closed system?

Accepted Answer

$\Delta E_{th} = W + Q$

Question 4

During an isochoric process, what is the work done on the gas?

Accepted Answer

$W = 0$

Question 5

A block is dragged across a rough surface and becomes warmer. The temperature increase occurs because of:

Accepted Answer

Work done on the block.

Question 6

For an isothermal compression of an ideal gas, which formula gives the work done on the gas?

Accepted Answer

$W = nRT \ln \left( \frac{V_i}{V_f} \right)$

Question 7

Two liquids, A and B, of equal mass and initial temperature are heated for the same time with identical burners. Afterward, liquid A is hotter than liquid B. Which has the larger specific heat?

Accepted Answer

Liquid B

Question 8

A 1 kg piece of silver ($c = 234 	ext{ J/kg K}$) at $100^\circ$C is placed in 1 kg of water ($c = 4190 	ext{ J/kg K}$) at $0^\circ$C in an insulated beaker. What is the final temperature?

Accepted Answer

Between $0^\circ$C and $50^\circ$C

Question 9

Which equation gives the amount of heat required to change the temperature of a mass $M$ of a substance by $\Delta T$?

Accepted Answer

$Q = Mc \Delta T$

Question 10

Which process is characterized by a change in thermal energy without a change in temperature?

Accepted Answer

Phase change

Question 11

A gas is rapidly compressed in a cylinder, with no heat exchange with the environment. What type of process is this?

Accepted Answer

Adiabatic

Question 12

During an adiabatic expansion of a gas, what happens to its temperature?

Accepted Answer

It decreases.

Question 13

Which formula gives the rate of heat transfer by conduction through a material of area $A$, thickness $L$, and thermal conductivity $k$, with temperature difference $\Delta T$?

Accepted Answer

$\frac{dQ}{dt} = \frac{kA \Delta T}{L}$

Question 14

If the temperature of the sun suddenly dropped to half its present value, by what factor would its power output decrease?

Accepted Answer

1/16

Question 15

Which equation gives the net rate of heat transfer by radiation between an object of area $A$ and temperature $T$ and its environment at temperature $T_{env}$?

Accepted Answer

$\frac{dQ}{dt} = e \sigma A (T^4 - T_{env}^4)$

Question 16

Which of the following statements about specific heats of gases is correct?

Accepted Answer

$C_p = C_v + R$

Question 17

A student catches the flu and his body temperature increases from $37.0^\circ$C to $39.0^\circ$C. If his mass is $70$ kg and the specific heat of the body is $3400$ J/kg K, how much energy is required for this temperature increase?

Accepted Answer

$Q = (70)(3400)(2.0) = 4.8 	imes 10^5$ J

Question 18

Which of the following mechanisms is NOT a way heat is transferred between a system and its environment?

Accepted Answer

Reflection

Question 19

A refrigerator uses the vaporization of Freon to cool the air. What physical principle is being exploited?

Accepted Answer

The heat of vaporization

Work, Heat, and the First Law of Thermodynamics – Chapter 19 Study Notes

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