Which observations correctly describe the second law of thermodynamics? Check all that apply.

Thermal energy that is not used to do work is often released to the surroundings.

Thermal energy flows from a cooler object to a warmer object.

Thermal energy flows from a warmer object to a cooler object.

Thermal energy is released as unusable energy by a heat engine, which is never 100 percent efficient.

Thermal energy flows when two objects in contact have a temperature difference.

Answers: 1,3,4,5

Thermal energy flows from a warmer object to a cooler object.

Explanation:

The second law of thermodynamics speaks about the direction of processes. Clarifying that these can only go in one direction as time progresses in one direction. To better understand this concept, several examples will be explained.

The first example is when we have a wood that we will use to make a campfire, as we require thermal energy to heat a space. We see that as the fire consumes the wood heat is generated inside the space. This will happen until the wood is consumed. Now if we want to perform the reverse process, that is to cool the room and use the heat content in this to generate wood, we see that it is an impossible process to perform, that is to say, it is true that this thermal process has only one direction.

Now suppose we have a cup of coffee at a temperature of 95 (°C), with the passage of time the coffee cools this is because it generates a heat transfer from the coffee to the surroundings. Similarly if we want to collect the heat from the surroundings and pass them to the coffee so that it reaches a temperature close to 95 (°C), naturally it can not be done, the heat transfer always exists in one direction this is from objects at high temperature to objects of lower temperature.

To violate the second law of thermodynamics, and to allow processes to go in the opposite direction, it is only possible through mechanical work that adheres to the process. For example if we have a canned drink at 25 (°C) and want to reduce the temperature of this drink, then we must put it in a refrigerator, so that it can reduce its temperature to 5 (°C). The refrigerator is electromechanical equipment that can alter heat transfer directions.

1, 3, 4, 5