Worth 50 points
1)going against the natural flow of heat and moving thermal energy from a low temperature to a high temperature is .
2)which are sources for thermal energy for a heat pump? check all that apply.
air
water
sunlight
ground
fire
3)a is formed from two pieces of different metals stuck together lengthwise.
bimetallic coil
coolant
heat pump
furnace
4)which burns fuel to release thermal energy?
refrigeration
combustion
coolant
thermostat
5)for which function is a heat engine most likely used?
starting an air conditioner
running a car
igniting a furnace
activating a thermostat
6)which best describes why heat pumps are reversible?
they can heat and cool an indoor space.
they involve a metal expanding or contracting against another.
they combust and can also add coolant.
they allow a piston to move up and down.
7)the thermal energy in a heat engine is used to move a piston. which best describes why this is possible?
the increase in thermal energy results in an increase in pressure.
the decrease in thermal energy results in an increase in pressure.
the increase in thermal energy results in a decrease in pressure.
the decrease in thermal energy results in a decrease in pressure.

1) We have that temperature naturally flows from areas that are hot to areas that are cold (this is a consequence of the 2nd law of thermodynamics). But this can change if we do not have a closed system, hence if we can change some of the conditions. A good completion would be: is possible only if the system is not closed/we add energy.
2) Air is apoor conductor and sunlight has barely enough concnetrated energy to make a heat pump work adequately. However, all other choices have worked. Hot water is used in several nuclear plant for heat pumps, fires are also used in simple mechanical systems and the ground heat has been used in hydrothermal vents etc.
3) A bimetallic coil is a coil that exemplifies the expansion of metals in the presence of heat and acts like an inaccurate thermometer. Since different metals expand at different speeds, the coil expands unequally when heated and ends up stretching.
4) Out of the 4 choices, refrigeration and coolant are inappropriate choices since they do not refer to release of hit but getting rid of heat. The thermostat also does not burn fuel, it jsut observes temperature. The correct answer is combustion which is defined as a cheical reaction that gives off heat and flame.
5) A heat engine by definitions converts heat into mechanical energy. We have that the only of the choices above that has as a product mechanical energy is the choice with the car, hence this is correct. An air conditioner is a heat pump, not a heat engine.
7) We have that by the law of chemistry, PV=nRT. and that the thermal energy is proportional to T. The pressure cannot increase without stop, so what we have when the temperature (thermal energy) goes up is that the volume also goes up. Hence, the correct answer is that an increase in thermal energy leads to an increase in pressure.