Physics Exam Review 1

A 4 mol ideal gas sytem undergoes an adiabatic process where it expands and does 20 J of work on its environment. What is the change in internal energy?

-20 J (negative work)

A heat engine performs 2000.0 j of net work while adding 5000 j of heat to the low-temperature reservoir. What is the efficiency of the engine?

.286 it would appear that 2000 J does useful work out of a total of 7000 J so efficiency = out put / in put 2000/7000 = eff

An engine absorbs 2150 J as heat from a hot reservoir and gives off 750 J as heat to a cold reservoir during each cycle. How much work is done during each cycle?

1400 J (2150-750)

A total of 165 J of work is done on a gaseous refrigerant as it undergoes compression. If the internal energy of the gas increases by 123 J during the process, what is the total amount of energy transferred as heat?

42 J (ΔU = ΔQ + ΔW 123 = ΔQ + 165)

A container of gas is at a pressure of 1.3x10^5 Pa and volume of 6.0 m^3. How much work is done by the gas if it expands at constant pressure to twice its initial volume?

7.8x10^5 (1.3...x 6)

The internal energy of a system is initially 63 J. A total of 71 J of energy is added to the system as heat while the system does 59 J of work. What is the system's final internal energy?

75 J (Ui+Q−W=Uf) 63J+71J−59J= 75 J) U=internal energy Q=heat energy

Over several cycles, a refrigerator does 1.73 x 104 J of work on the refrigerant. The refrigerant removes 8.11 x 104 J as heat from the air inside the refrigerator. How much energy is delivered to the outside air?

9.84 x 10^4 J (add them)

Which of the following is a thermodynamic process during which work is done on or by the system but no energy is transferred to or from as heat?

Adiabatic Process

According to the second law of thermodynamics, what applies for any process that can occur within an isolated system?

Entropy increases

In an isovolumetric process by an ideal gas, the systems/ heat gain is equal to a change in what?

Internal Energy

According to the first law of thermodynamics, the difference between energy transferred to and from a system as heat, and energy transferred by work is equivalent to what?

Internal energy change

Which process for an ideal gas system has an unchanging internal energy and a heat intake that corresponds to the value of the work done by the system?

Isothermal Process

A thermodynamic process that takes place at a constant temp and where the internal energy remains unchanged.

Isothermal process

A thermodynamic process that takes place at a constant volume so no work is done on or by the system

Isovolumetric process

A thermodynamics process occurs, and the entropy of the system decreases. What can be concluded about the entropy change?

It increases

A chunk of ice with a mass of 1 kg at 0*C melts and absorbs 3.35 x 10^8 J of heat. Which best describes what happened to the system?

Its entropy increased.

Imagine you could observe the individual atoms that make up a piece of matter and that you observe the motion of the atoms becoming more orderly. What can you assume about the system?

Its entropy is decreasing.

An electrical power plant manages to transfer 88 percent of the heat produced in the burning of fossil fuel to convert water to steam. Of the heat carried by the steam, 40 percent is converted to the mechanical energy of the spinning turbine. Which best describes the !overall! efficiency of the heat-to-work conversion in the plant?

Less then 40%

The requirement that a heat engine must give up some energy at a lower temp. in order to do work corresponds to which law of thermo?

Second

According to the second law of thermodynamics, the heat received by a heat engine operating in complete cycle from a high-temp reservoir...

cannot be completely converted to work

When an egg is broken and scrambled, the entropy of the system...

increases, and the total entropy of the universe increases.

When a system's disorder is increased...

less energy is available to do work

When all the entropy changes in a process are included...

the increases in entropy are always greater then the decreases

If an ideal gas does positive work on its surrounding, then

the volume of the gas increases