the first law of thermodynamics

Examples of the first law of thermodynamics in the following topics:

• The First Law of Thermodynamics

  • The first law of thermodynamics states that energy can be transferred or transformed, but cannot be created or destroyed.
  • The first law of thermodynamics deals with the total amount of energy in the universe.
  • According to the first law of thermodynamics, energy can be transferred from place to place or changed between different forms, but it cannot be created or destroyed.
  • The first law of thermodynamics tells us that energy can neither be created nor destroyed, so we know that the energy that is absorbed in an endothermic chemical reaction must have been lost from the surroundings.
  • Another useful form of the first law of thermodynamics relates heat and work for the change in energy of the internal system:

• The First Law

  • The first law of thermodynamics is a version of the law of conservation of energy specialized for thermodynamic systems.
  • The first law of thermodynamics applies the conservation of energy principle to systems where heat transfer and doing work are the methods of transferring energy into and out of the system .
  • In equation form, the first law of thermodynamics is
  • The change in the internal energy of the system, ΔU, is related to heat and work by the first law of thermodynamics, ΔU=Q−W.
  • Explain how the net heat transferred and net work done in a system relate to the first law of thermodynamics

• Energy Transformations

  • Energy transformation occurs when energy is changed from one form to another, and is a consequence of the first law of thermodynamics.
  • It is a consequence of the first law of thermodynamics that the total energy of a given system can only be changed when energy is added or subtracted from the system.
  • For example, the theoretical limit of the energy efficiency of a wind turbine (converting the kinetic energy of the wind to mechanical energy) is 59%.
  • This corresponds to zero kinetic energy and thus all of the energy of the pendulum is in the form of potential energy.
  • Summarize the consequence of the first law of thermodynamics on the total energy of a system

• The Second Law

  • The first law of thermodynamics would allow them to occur—none of those processes violate conservation of energy.
  • The law that forbids these processes is called the second law of thermodynamics .
  • The already familiar direction of heat transfer from hot to cold is the basis of our first version of the second law of thermodynamics.
  • The Second Law of Thermodynamics(first expression): Heat transfer occurs spontaneously from higher- to lower-temperature bodies but never spontaneously in the reverse direction.
  • Contrast the concept of irreversibility between the First and Second Laws of Thermodynamics

• The Three Laws of Thermodynamics

  • The laws of thermodynamics define fundamental physical quantities (temperature, energy, and entropy) that characterize thermodynamic systems.
  • The first law of thermodynamics, also known as Law of Conservation of Energy, states that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another.
  • A way of expressing the first law of thermodynamics is that any change in the internal energy (∆E) of a system is given by the sum of the heat (q) that flows across its boundaries and the work (w) done on the system by the surroundings:
  • The second law of thermodynamics says that the entropy of any isolated system always increases.
  • The third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero.

• Human Metabolism

  • The 1st law of thermodynamics explains human metabolism: the conversion of food into energy that is used by the body to perform activities.
  • It is an example of the first law of thermodynamics in action.
  • Considering the body as the system of interest, we can use the first law to examine heat transfer, doing work, and internal energy in activities ranging from sleep to heavy exercise.
  • Both applications of the first law of thermodynamics are illustrated in .
  • (a) The first law of thermodynamics applied to metabolism.

• Isothermal Processes

  • An isothermal process is a change of a thermodynamic system, in which the temperature remains constant.
  • The value of the constant is nRT, where n is the number of moles of gas present and R is the ideal gas constant.
  • In other words, the ideal gas law PV = nRT applies.
  • In thermodynamics, the work involved when a gas changes from state A to state B is simply
  • From the first law of thermodynamics, it follows that $Q =-W$ for this same isothermal process.

• A Review of the Zeroth Law

  • Zeroth law justifies the use of thermodynamic temperature, defined as the shared temperature of three designated systems at equilibrium.
  • This law was postulated in the 1930s, after the first and second laws of thermodynamics had been developed and named.
  • It is called the "zeroth" law because it comes logically before the first and second laws (discussed in Atoms on the 1st and 2nd laws).
  • A brief introduction to the zeroth and 1st laws of thermodynamics as well as PV diagrams for students.
  • Discuss how the Zeroth Law of Thermodynamics justifies the use of thermodynamic temperature

• The Zeroth Law of Thermodynamics

  • The Zeroth Law of Thermodynamics states that systems in thermal equilibrium are at the same temperature.
  • There are a few ways to state the Zeroth Law of Thermodynamics, but the simplest is as follows: systems that are in thermal equilibrium exist at the same temperature.
  • What the Zeroth Law of Thermodynamics means is that temperature is something worth measuring, because it indicates whether heat will move between objects.
  • However, according to the Zeroth Law of Thermodynamics, if the systems are in thermal equilibrium, no heat flow will take place.
  • There are more formal ways to state the Zeroth Law of Thermodynamics, which is commonly stated in the following manner:

• Changes in Energy

  • The concept of entropy evolved in order to explain why some processes (permitted by conservation laws) occur spontaneously while their time reversals (also permitted by conservation laws) do not; systems tend to progress in the direction of increasing entropy.
  • This fact has several important consequences in science: first, it prohibits "perpetual motion" machines; and second, it implies the arrow of entropy has the same direction as the arrow of time.
  • In classical thermodynamics the entropy is interpreted as a state function of a thermodynamic system.
  • The entropy of the thermodynamic system is a measure of how far the equalization has progressed.
  • The second law of thermodynamics shows that in an isolated system internal portions at different temperatures will tend to adjust to a single uniform temperature and thus produce equilibrium.