How is the kinetic energy of the particles that make up a substance different after it changes state?
O A. The kinetic energy is greater after a substance changes from a
plasma to a gas.
O B. The kinetic energy is greater after a substance changes from a
liquid to a solid.
O C. The kinetic energy is less after a substance changes from a liquid
to a gas.
O D. The kinetic energy is less after a substance changes from a gas to
a liquid.

As part of an industrial process, air as an ideal gas at 10 bar, 400k expands at steady state through a valve to a pressure of 4 bar. the mass flow rate of air is 0.5 kg/s. the air then passes through a heat exchanger where it is cooled to a temperature of 295k with negligible change in pressure. the valve can be modeled as a throttling process, and kinetic and potential energy effects can be neglected. (a) for a control volume enclosing the valve and heat exchanger and enough of the local surroundings that the heat transfer occurs at the ambient temperature of 295 k, determine the rate of entropy production, in kw/k. (b) if the expansion valve were replaced by an adiabatic turbine operating isentropically, what would be the entropy production? compare the results of parts (a) and (b) and discuss.

Consider an insulating crystal, made up of layers of atoms. what form would you expect the temperature dependence of the phonon heat capacity to approach at extremely low temperatures if the interlayer coupling is i)very strong (rigid coupling), and ii) very weak. explain.

If two parallel light rays hit a mirror, they will not be parallel to each other after they reflect.