Physics 3.4 Second Law of Thermodynamics

What is the heat energy required to completely vaporize 10g of water beginning at 0°C? (The heat capacity of water is 4.2 J/g⋅K and the ΔHvaporization​ of water is 2260 kJ/kg) A. 4.9 kJ B. 26.8 kJ C. 228.1 kJ D. 2126 kJ

B. 26.8 kJ First, use q=mc(delta)T, then q=mL for a phase change

When energy is put into a system, entropy...

increases

Describe entropy on a macroscopic level and in statistical terms.

Macroscopic Level: Tendency toward disorder Statistical: the measure of the spontaneous dispersal of energy at a specific temperature , increasing the number of available microstates for a given molecule

When energy leaves a system, entropy....

decreases

Natural Process

irreversible process

Entropy Equation

ΔS=Q/T (in K) delta S= change in entropy Q= heat gained or lost in a reversible process T=temp in K

What is the net work on the gas from point A to B?

-200J

What is the net work on the gas from points C to D to E?

500J

What is the final temperature of a 3 kg wrought iron fireplace tool that is left in front of an electric heater absorbing heat energy at a rate of 100 W for 10 minutes? Assume the pendant is initially at 20 degrees C and that the specific heat of wrought iron is 500 J/kg-K A. 40 degrees C B. 50 degrees C C. 60 degrees C D. 70 degrees C

A. 40 degrees C First take 100 W x 10min x 60s/min Then use q=mcdeltaT

When heating a solution, a scientist detects a temperature increase in the solution during a period of time. Which of the following statements accurately characterizes the solution during this period? A. The velocity of molecules in the solution is increasing. B. The solution is undergoing a phase change. C. The solution is at boiling point. D. The solution's temperature increase is proportional to its ΔHvaporization​.

A. The velocity of molecules in the solution is increasing. During a phase change, temperature remains constant.

Which of the following is not a state function? A. Internal energy B. Heat C. Temperature D. Entropy

B. Heat

A 20 m steel rod at 10 degrees C. is dangling from the edge of a building and is 2.5 cm from the ground. If the rod is heated to 110 degrees C, will the rod touch the ground? A. Yes, because it expands by 3.2 cm B. Yes, because it expands by 2.6 cm C. No, because it expands by 2.2 cm D. No, because it expands by 1.8 cm

C. No, because it expands by 2.2 cm Use deltaL=ALdeltaT

In an adiabatic compression process, the internal energy of the gas: a. increases because the work done on the gas is negative b. increases because the work done on the gas is positive c. decreases because the work done on the gas is negative d. decreases because the work done on the gas is positive

b. increases because the work done on the gas is positive delta U=W, because no heat transfer is involved work done on the system is positive

Second Law of Thermodynamics

states that objects in thermal contact(not in thermal equilibrium) will exchange heat energy such that the object with a higher temperature will give off heat energy to the object with a lower temperature until both objects reach equilibrium (Heat always flows from hot to cold objects)

Which of the following scenarios violates the first law of thermodynamics, "the conservation of energy?" A. An isolated electrochemical cell that indefinitely generates an electrical current. B. An efficient wind turbine that converts all of its energy from mechanical movement into electrical potential energy. C. A machine that converts heat energy into work energy. D. A spring that extends and retracts forever, alternating between potential and kinetic energy.

A. An isolated electrochemical cell that indefinitely generates an electrical current. If the cell is in an isolated system, it can not indefinitely generate more energy.

A certain substance has a specific heat of 1 J/mol-K and a melting point of 350 K. If one mole of the substance is currently at a temperature of 349 K, how much energy must be added in order to melt it? A. More than 1 J B. Exactly 1 J C. Less than 1 J but more than 0 J D. Less than 0 J

A. More than 1 J

In a system undergoing adiabatic compression, what are the values of internal energy and heat if work done on the system is 500J? A. Internal energy is 0J and heat is 500J. B. Internal energy is 500J and heat is 0J. C. Internal energy is 0J and heat is -500J. D. Internal energy is -500J and heat is 0J.

B. Internal energy is 500J and heat is 0J. Adiabatic process equals no heat transfer deltaU=Q-W, so in adiabatic processes, deltaU=-W Compression =work done on the system (-500J) deltaU=-(-500J) =500J

Atmospheric gases absorb more energy than they emit. If we consider a gas to be a closed system, which of the following is true? A. The change in volume of the gas is negative. B. The heat absorbed by the gas is positive. C. The work done on the gas is equal to the change in internal energy and the heat absorbed by the gas. D. The internal energy of the gas increases.

B. The heat absorbed by the gas is positive. When there is heat entering into the system, q is positive.

Compared to the initial value, what is the resulting pressure for an ideal gas that is compressed isothermally to one-third of its initial volume? A. Equal B. Three times larger C. Larger, but less than three times larger D. More than three times larger

B. Three times larger

The entropy of a system can: A. never decrease B. decrease when the entropy of the surroundings increases by at least as much C. decrease when the system is isolated and the process is irreversible D. decrease during an adiabatic reversible process

B. decrease when the entropy of the surroundings increases by at least as much

Entropy

a measure of the spontaneous dispersal of energy at a specific temperature (how much energy has spread out, or how spread out energy has become)

In experiment A, a student mixes ink with water and notices that the two liquids mix evenly. In experiment B, the student mixes oil with water; in this case, the liquids separate into two different layers. The entropy change is: A. positive in A and negative in B B. positive in A and zero in B C. negative in A and positive in B D. zero in A and negative in B

B. positive in A and zero in B

Unnatural Process

Processes that are generally reversible, Ex : Hot object in contact with cold object becomes hotter while cold object gets colder

How much heat is required to completely melt 500 g of gold earrings, given that their initial temperature is 25 degrees C? (The melting point of gold is 1064 degrees C, its heat of fusion is 6.37 x 10^4 J/kg, and its specific heat is 126 J/kg -K) A. 15 kJ B. 32 kJ C. 66 kJ D. 97 kJ

D. 97 kJ First, use q=mcat, then use q=mL for the phase change Then add the two results together to get the total heat

A hot object is placed next to a cold object so that they are touching. Which of the following statements is true? I. Heat will transfer from the hot object to the cold object because the hot object has a higher temperature. II. The two objects are in thermal equilibrium. III. Internal energy will transfer from the hot object to the cold object because the hot object has greater internal energy.

I. only Internal energy does not transfer from hot to cold objects

What is the relationship between the entropy of a system and its surroundings for any thermodynamic process?

The entropy of a system and its surroundings will never decrease; it will always remain zero or increase.

Second law of Thermodynamics (Equation)

deltaS(universe) = deltaS(system) + deltaS(surroundings) > 0

Second Law of Thermodynamics (Energy)

energy spontaneously disperses from being localized to being spread out if it is not hindered to do so

Which of the following choices correctly identifies the following three heat transfer processes? I. Heat transferred from the dun to the earth II. A metal spoon heating up when placed in a pot of hot soup III. A rising plume of smoke from a fire A. Radiation, Conduction, Convection B. Conduction, Radiation, Convection C Radiation, Convection, Conduction D. Convection, Conduction, Radiation

A. Radiation, Conduction, Convection

A student making a coffee cup calorimeter fails to use a second coffee cup and inadequately seals the lid. What was her initial goal, and what was the result of the mistake? A. She was trying to create an isolated system, but created an open system. B. She was trying to create an isolated system, but created a closed system. C. She was trying to create a closed system, but created an open system. D. She was trying to create a closed system, but created an isolated system.

A. She was trying to create an isolated system, but created an open system.

If an object with an initial temperature of 300K increases its temperature by 1 degree C every minute, by how many degrees Fahrenheit will its temperature have increased in 10 minutes?

C. 18 degrees Fahrenheit 1 degrees Celsius= 1.8 degrees Fahrenheit

Which of the following is least likely to be accompanied by a change in temp? A. The kinetic energy of a gas is increased through a chemical reaction B. Energy is transferred to a solid via electromagnetic waves C. A boiling liquid is heated on a hot plate D. A warm gas is mixed with a cold gas

C. A boiling liquid is heated on a hot plate

Substances A and B have the same freezing and boiling points. If solid samples of both substances are heated in the same way, substance A boils before substance B. Which of the following would NOT explain this phenomenon? A. Substance B has a higher specific heat B. Substance B has a higher heat of vaporization C. Substance B has a higher heat of fusion D. Substance B has a higher internal energy

D. Substance B has a higher internal energy

Equal amounts of heat are absorbed by 100 g samples of various solid metals with differing specific heat values. Which of the following statements is true regarding metals and their specific heat values? A. The metal with the greatest specific heat will resist melting to a greater degree at its melting point. B. The metal with the smallest specific heat will undergo the smallest change in temperature. C. The metal with the smallest specific heat will resist melting to a greater degree at its melting point. D. The metal with the greatest specific heat will undergo the smallest change in temperature.

D. The metal with the greatest specific heat will undergo the smallest change in temperature.

Additional gas is pumped inside a rigid container that stores compressed gas. Which of the following is a true statement about this system? A. Pressure is constant throughout the compression. B. The molar concentration of gas is decreasing. C. The volume of the container is decreasing. D. There is no work done on the container.

D. There is no work done on the container. For work to be done, there must be a change in volume. Since the container is rigid, it has a fixed volume.