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The Three Laws of Thermodynamics: Applications and Overview

Maram Ghadban, Robert Egan, Christianlly Cena
  • Author
    Maram Ghadban

    A freelance tutor equipped with a bachelor's of science in chemical engineering. Graduated from the American University of the Middle East with a GPA of 3.87, performed a number of scientific primary and secondary research. Tutored university level students in various courses in chemical engineering, math, and art. Has experience tutoring middle school and high school level students in science courses.

  • Instructor
    Robert Egan
  • Expert Contributor
    Christianlly Cena

    Christianlly has taught college Physics, Natural science, Earth science, and facilitated laboratory courses. He has a master's degree in Physics and is currently pursuing his doctorate degree.

Explore how the laws of thermodynamics function in everyday life, review the three laws of thermodynamics, and learn about energy in a closed system. Updated: 12/16/2021

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Thermodynamics

Thermodynamics is a science discipline that studies the relationship of heat, work, and temperature and examines how these variables are related to other parameters like entropy, properties of matter, energy, and radiation. The law of thermodynamics definition is the principles that govern the behavior of an observed system and its interaction with the surroundings.

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  • 0:03 Laws in Everyday Llife
  • 0:40 First Law of Thermodynamics
  • 3:21 Second Law of Thermodynamics
  • 4:44 Energy in a Closed System
  • 7:12 Lesson Summary
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The Three Laws of Thermodynamics

What are the three laws of thermodynamics? The three laws of thermodynamics are the set of principles that describe thermodynamic systems. The laws assess the system's ability to perform useful work by studying how the system's energy changes with other variables. In order to observe how certain variables impact others, thermodynamics have divided the universe into two parts—the system and the surroundings.

The system is the selected part of the universe that is being studied. The system can be any part of the physical universe whose thermodynamics properties are a subject of study. The surroundings are the remaining part of the universe that is separated from the system by a hypothetical boundary. The table serves as a reminder of the types of systems in thermodynamics.

Closed System Open System Isolated System
A system where there is energy transfer but no matter transfer (matter is conserved) A system where there is matter and energy transfer in and out the system A system where neither matter nor energy transfers outside the system's boundaries

Figure 1: In thermodynamics, the universe is divided into system and surroundings

Thermodynamics system and surroundings

The First Law of Thermodynamics

What are the first and second laws of thermodynamics? The first law of thermodynamics, alternatively known as the 'Law of Conservation of Energy', states that the total energy in an isolated system is conserved:

{eq}E_{system} + E_{surroundings} = Constant {/eq}

In other words, the universe's total energy is constant; it does not change, because energy cannot be created nor destroyed. One of the appropriate thermodynamics examples that best explain the first law is electricity. Electricity is used to power many appliances, but where does this electricity come from? The sources of much electricity are powerplants; there are plants that generate electricity from nuclear materials, and others that use kinetic energy. A hydroelectric plant is an example of the latter type: dams act as reservoirs that block rivers. The dam converts the river's kinetic energy to potential energy, so that when the water is released it would flow down the pipes that lead to the turbine. The water pushes the turbine blades to generate electricity in the generator. What happened here is that the water's kinetic energy made the turbine spin to produce electricity in the generator. The electricity is then distributed in commercial and residential areas where it is used to power appliances.

Figure 2: Electricity is generated in hydroelectric plants

Real life first law of thermodynamics example

To summarize, the dam converts the river's kinetic energy, which is the energy generated from moving bodies, to potential energy, which is the stored energy of a body relative to its position. The potential energy is used in spinning the turbine, which in turn leads to the generation of electricity.

Electricity is a form of energy that cannot be created nor destroyed; it did not conjure itself out of nothing to power computers and fridges. It was produced originally from kinetic energy (the starting point). The electricity generated does not dissipate into nothing nor is it 'lost' to the surroundings; the electricity in light bulbs just transforms into a different form of energy, light, and heat.

What the first law shows is that energy is never lost nor is it created out of nothing; it simply transforms from one form to another.

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Laws of Thermodynamics True or False Activity

This activity will help you assess your knowledge of the first and second laws of thermodynamics.

Directions

Determine whether the following statements are true or false. To do this, print or copy this page on a blank paper and underline or circle the answer.

1. Thermodynamics deals with the relationships between heat and other forms of energy.

True | False

2. The energy that an object possesses due to its motion is known as potential energy.

True | False

3. Kinetic energy is dependent on two things: the weight and the speed of the object, respectively.

True | False

4. Hydroelectric energy generates electricity by converting the energy of moving water.

True | False

5. From the second law of thermodynamics, the total energy is equal to the free energy plus the usable energy in the system.

True | False

6. A force that resists the relative motion or tendency to such motion of two bodies in contact is known as friction.

True | False

7. Heat is another example of kinetic energy.

True | False

8. Kinetic energy can be transformed into kinetic energy, and vice versa.

True | False

9. The first law of thermodynamics is often referred to as the law of conservation of energy.

True | False

10. As stated in the first law, the entropy of a system increases over time.

True | False


Answer Key

  1. True
  2. False, because the correct statement is, The energy that an object possesses due to its motion is known as kinetic energy.
  3. False, because the correct statement is, Kinetic energy is dependent on two things: the mass and the speed of the object respectively.
  4. True
  5. False, because the correct statement is, From the second law of thermodynamics, the total energy is equal to the free energy plus the unusable energy in the system.
  6. True
  7. False, because the correct statement is, Heat is not an example of kinetic energy.
  8. True
  9. True
  10. False, because the correct statement is, As stated in the second law, the entropy of a system increases over time.

What are the real life examples of the first law of thermodynamics?

A real life example of the first law is electricity. Electricity can be produced in hydroelectric plants, which use dams to convert the river's kinetic energy to potential energy. This is then used to push down the turbine's blades to power the generator to produce electricity. The electricity is then distributed to commercial and residential areas where it is used to power appliances. The electricity does not disappear upon powering some devices; electricity is converted to thermal and light energies in light bulbs.

What are the first, second, and third laws of thermodynamics?

  • The first law of thermodynamics states that the energy of an isolated system is conserved; it cannot be created nor destroyed, but it can transform from one form of energy to another.
  • The second law of thermodynamics states that entropy increases with time; not all the energy is used to perform useful work.
  • The third law of thermodynamics states that at the absolute zero; the entropy of the system reaches a constant value. The absolute zero is the lowest temperature possible.

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