GENERAL CHEMISTRY

• The study of energy and its transformation is known as thermodynamics. This area of study began during the Industrial Revolution in order to develop the relationships among heat, work and fuels in steam engines.
• The first law of thermodynamics states that energy can neither be created nor destroyed, it can only be transformed from one form to another. This is also known as the Law of Conservation of Energy.
• This law says that there are two kinds of processes, heat and work, that can lead to a change in the internal energy of the system. Since both heat and work can be measured and quantified, this is the same as saying that any change in the energy of a system must result in a corresponding change in the energy of the surroundings outside the system. In other words, energy cannot be created or destroyed.
• Heat and work are two kinds of processes that define the change in the internal energy.
• If the heat flows into a system or the surroundings do work on it, internal energy increases and the values of the q and w are positive.
• Heat flow out of the system or work done by the system on the surroundings, the internal energy decreases because q and w are both negative.
• Change in Internal Energy is used in expressing the first law of thermodynamics, wherein change in the internal energy(   E) is the sum of the heat (q) that flows across its boundaries and the work (w) done on the system by the surrounding

  Mathematically it is expressed as:

     E= q + w
• The second law of thermodynamics puts restrictions upon the direction of heat transfer and achievable efficiencies of heat engines. The first law of thermodynamics states that the energy of the universe remains constant; though energy can be exchanged between system and surroundings, it can’t be created or destroyed.
• The second law of thermodynamics states that any spontaneously occurring process will always lead to an escalation in the entropy (S) of the universe. In simple words, the law explains that an isolated system’s entropy will never decrease over time.
• , in some cases, where the system is in thermodynamic equilibrium or going through a reversible process, the total entropy of a system and its surroundings remains constant. The second law is also known as the Law of Increased Entropy.
• The second law of thermodynamics states that it is impossible to convert heat energy to mechanical energy with 100 per cent efficiency.
• In an engine, the gas is heated to increase its pressure and drive the piston.
• The first law of thermodynamics does not indicate whether a metallic bar of uniform temperature can spontaneously become warmer at one end and cooler at others.
• Heat generated from friction that is generally unusable should also be removed from the system.
• All that the first law of thermodynamics can state is that there will always be an energy balance if the process occurs.
• The second law of thermodynamics provides the criterion for the feasibility of any process.
• A process cannot occur unless it satisfies both the first and second laws of thermodynamics.
• Entropy is a measure of the randomness of the system, or it is the measure of energy or chaos within an isolated system.
• Entropy can be considered a quantitative index that describes the quality of energy.
• In a closed system, while the mass remains constant, there is an exchange of heat with the surroundings.
• The change in the heat content creates a disturbance in the system, thereby increasing the entropy of the system.
• Internal changes may occur in the movements of the molecules of the system.
• These changes lead to disturbances which further cause irreversibilities inside the system resulting in the increment of its entropy.
• There are two statements on the second law of thermodynamics, and they are

  1. Kelvin- lank Statement
  2. Clausius Statement
• Kelvin-Planck Statement

  It is impossible for a heat engine to produce a network in a complete cycle, if it exchanges heat only with bodies at a single fixed temperature.
• Clausius’s Statement states that it is impossible to construct a device operating in a cycle that can transfer heat from a colder body to a warmer one without consuming any work.
• Clausius’s Statement also states that energy will not flow spontaneously from a low-temperature object to a higher-temperature object.
• Clausius’s Statement refers to the net transfer of energy.
• Energy transfer can take place from a cold object to a hot object by the transfer of energetic particles or electromagnetic radiation.
• The net transfer will occur from the hot object to the cold object in any spontaneous process.
• Some form of work is needed to transfer the net energy to the hot object.
• Unless the compressor is driven by an external source, the refrigerator won’t be able to operate.
• The heat pump and refrigerator work on Clausius’s Statement.