"6. D is correct. The heat released when steam is condensed in the condenser is dissipated through the walls of the system to the external environment and thus is wasted energy. This makes choice A an invalid statement. Both a gas and a liquid are fluids, so both are capable of flowing through the pump. The density of a liquid does not necessarily impact the ease with which it flows. The ease with which it flows depends on its viscosity, which may or may not parallel density. This eliminates choice B. The piston in the cylinder is hot from the steam, so condensing gas in a nearby chamber does not affect the temperature of the piston. The boiling point of water and the condensation temperature of steam are both 100?C, so the chambers adjacent to the piston are at 100?C. The piston is likely going to be at 100?C, so condensing the steam in the condenser does not result in a decrease in the temperature of the piston. Choice C is an invalid statement. When the vapor is condensed into a gas, the pressure in the condenser is reduced. This results in the pressure in the condenser being lower than the pressure in the piston. Because of the pressure differential between the piston chamber and the condenser, steam flows from the piston through the exhaust port and into the condenser (from a region of higher pressure to a region of lower pressure). Flow is made easier, when the exhaust gas is condensed into a liquid once inside of the condenser. The correct choice is D."
