Physics Thermodynamics Review

A rocket engine acquires motion by ejecting hot gases in the opposite direction.

This is an example of which law?

• Conservation of mass

• Conservation of heat

• Conservation of energy

• Conservation of momentum

The Law of Conservation of Momentum applies to an isolated system only when

• there is a loss of kinetic energy

• there is a gain in kinetic energy

• there is no external forces acting on it

• there is no internal forces acting on it

A bowl of hot soup and a glass of ice water are left in a room.

Eventually the soup and the water becomethe same temperature as their surroundings.

Which of the following explains the flow of heat that led to this final outcome?

• The heat of the soup and the cold of the water were exchanged, cancelling each other out.

• Heat energy went from the soup to the room and from the room into the ice water.

• Heat energy went from the ice water to the soup and from the soup to the room.

• The low temperature of the water was transferred to the room and from the room to the soup.

Which of the following describes a situation that would violate the law of entropy?

• Cold water, taken from the refrigerator, eventually reaches room temperature

• An iron bar placed in a room becomes cooler than its surroundings.

• A metal pan, heated on the stove, cools off when removed from the burner

• Iced tea and hot coffee, left of a table, reach the same temperature

Which of the following statements is not true with regards to the first law of thermodynamics?

• The first law of thermodynamics states that within an open system, the total energy of that system will remain constant

• A change in internal energy can be calculated if you know how much energy was transferred in the form of heat, and how much energy was used created in the form of mechanical work

• With regards to heat flow, if a system is heated, the energy will move from the surroundings to the sytem

• You can calculate the change of enthalpy of a system(the change in heat content of the system) by calculating the heat flow of the system. The heat flow is represented byt he letter (q).

How can popcorn be made using conduction?

• Placing in under a heat lamp

• Popping it in a microwave

• Heating it with hot air

• Cooking in in a hot pan

NASA developed a reflective foil barrier to help shield spacecraft from heat transfer in space. These

reflective barriers are now used in homes to prevent heat transfer by the same method. What method of heat transfer is being prevented by the reflective barrier?

• Conduction

• Convection

• Entropy

• Radiation

A tray filled with ice is removed from the freezer. After a short period of time, the ice begins to melt.

As the ice melts, it ―

• Decreases in specific heat capacity

• Decreases in temperature

• Increases in entropy

• Decreases in entropy

In the lab, a student places a 5 kg container of water on a hot plate. The heating of the water is

constant. The student records the temperature and graphs it as a function of time on the graph below. Accoring to the graph, which change will likely require the most heat

• A-->B

• B-->C

• C-->D

• D-->E

A student that just received their driver’s license decides to buy a new car. remembers from physics

class that heat engines have a thermal efficiency that can be calculated. He asks the car dealer for a

car that has a high thermal efficiency rating. The car dealer says he has a car that is 100% efficient.

Which law of thermodynamics best describes why the car cannot be 100% efficient?

• The zeroth law of thermodynamics

• The first law of thermodynamics

• The second law of thermodynamics

• The third law of thermodynamics