The laws of thermodynamics

If an ideal gas is compressed isothermally, which of

the following statements is true?

• Energy is transferred to the gas by heat.

• No work is done on the gas.

• The temperature of the gas increases.

• The internal energy of the gas remains constant.

• None of those statements is true

Tags

NGSS.HS-PS3-4

When an ideal gas undergoes an adiabatic expansion, which of the following statements is true?

• The

  temperature of the gas doesn’t change

• No work is done by the gas.

• No energy is delivered to the gas by heat

• The internal energy of the gas doesn’t change.

• The pressure increases

By visual inspection, order the PV diagrams shown in Figure 12.4 from the most negative work done on the system to the most positive work done on the system.

• a, b, c, d

• a, c, b, d

• d, b, c, a

• d, a, c, b

When an ideal gas expands at constant pressure, the change in the internal energy must be positive.

• True

• False

What is the equation for the first law of thermodynamics?

• $\Delta U=Q-W$

• $Q=\Delta U+W$

• $W=Q-\Delta U$

• $W=\Delta U-Q$

A gas is heated by supplying it with 250 kJ of

energy; at the same time, it is compressed

so that 500 kJ of work is done on the gas.

Calculate the change in the internal energy of

the gas.

• 250 kJ

• 750 kJ

• -250 kJ

• 500 kJ

Tags

NGSS.HS-PS3-1

A heat engine

• converts heat input to an equivalent amount of work

• converts work to an equivalent amount of heat

• takes heat in, does work, and loses energy heat

• uses positive work done on the system to transfer heat from a low temperature reservoir to a high temperature reservoir

• uses positive work done on the system to transfer heat from a high temperature reservoir to a low temperature reservoir

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-4

A Carnot cycle

• is bounded by two isotherms and two adiabats on a p-V graph

• consists of two isothermal and two constant volume processes

• is any four sided process on a p-V graph

• only exists for an ideal gas

• has an efficiency equal to the enclosed area on a p-V diagram

A Carnot engine operates between 200°C and 20°C. Its maximum possible efficiency is

• 90%

• 100%

• 38%

• 24%

• 72%

Which of the following statements best describes the Second Law of Thermodynamics?

• The internal energy of the universe is constant.

• Energy can be neither created nor destroyed.

• When an isolated system undergoes a spontaneous change, the entropy of the system will increase.

• At absolute zero, the entropy of a perfect crystal is considered to be zero.

Tags

NGSS.HS-PS3-4