# Thermodynamics

Introduction:

Thermodynamics is the study of energy which can exist in many forms, such as heat, light, chemical energy, and electrical energy. The variables that thermodynamics can be used to define include temperature, internal energy, entropy, and pressure. Temperature, relating to thermodynamics, is the measure of kinetic energy in the particles of a substance. Light is usually linked to absorbance and emission in thermodynamics while pressure, linked with volume, can do work on an entire system. The entropy is the measure of the flow of heat through a system whose equation is for a thermodynamically reversible process as

Regarding thermodynamics, there are three laws the first of which is appropriately named the First Law of Thermodynamics. The First Law of Thermodynamics states that energy can be changed from one form to another, but it cannot be created or destroyed. The total amount of energy and matter in the Universe must remains constant at all times, however it can change from one form to another. In other words energy is always conserved with the amount remaining constant. The Second Law of Thermodynamics states that in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state also referred to as entropy. The third law of thermodynamics is that the entropy of a perfect crystal at absolute zero is exactly equal to zero. When a system is at zero kelvin, the system will be in a state with the least possible energy. The third law is true if and only if the perfect crystal has only one minimum energy state. The entropy is zero because it only has one microstate. In simple terms the entropy of a system approaches a constant value as the temperature approaches zero. Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure, which enthalpy is greatly affected by. The unit of measurement for enthalpy is the joule since enthalpy is the measure of energy. With simplicity, enthalpy is energy transfer. Enthalpy accounts for energy transferred to the environment through the expansion of the system. The total enthalpy of a system, written as H, of a system cannot be measured directly so the change in enthalpy, written as ΔH, is more commonly used. The change ΔH is positive in endothermic reactions, and negative in exothermic processes which is a process that releases heat. The ΔH of a system is equal to the sum of work done on it and the heat supplied to it. For processes under constant pressure, ΔH is equal to the change in the internal energy of the system, in addition to the work that the system has done on its surroundings so the change in enthalpy would be the heat absorbed or released by a chemical reaction. The equation for enthalpy is as H=U+pV Equation 1 where H is the enthalpy of the system, U is the internal energy of the system, p is the pressure of the system, and V is the volume of the system. An equation for the change in enthalpy is ∆H=Hf-HI Equation 2 where delta H is the change in enthalpy. Hess’s Law states that if several reactions add up to produce an overall reaction, then the heat transfers of the reaction will add up to the value of the heat transfer of the total reaction. With relation to this lab, the enthalpy changes for the reaction of ammonia and hydrochloric acid can be determined using...

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