The Nature of Energy Thermodynamics is the study of energy changes accompanying physical and chemical changes Heat and work are both forms of energy They are also related forms in that one can be transformed into the other Heat energy can be used to do work Work can be transformed into heat Energy is the capacity to do work or to transfer heat It is a known fact that energy can be trans ferred from one piece of matter to another There are six forms of energy they are listed below 1 Mechanical Energy Mechanical energy is the sum of potential energy and kinetic energy present in the components of a mechanical system 2 Thermal Energy Thermal energy is the part of the total internal energy of a thermodynamic system 3 Chemical Energy Chemical energy is the potential of a chemical substance to undergo a transformation 4 Electrical Energy Electrical potential energy is a potential energy measured in joules that results from Coulomb forces 5 Nuclear Energy Nuclear power is the use of sustained nuclear fission to generate heat and do useful work 6 Solar Energy Solar energy is energy derived from the Sun s radiation Kinetic Energy is the energy of motion The formula used to figure out kinetic energy is Ek 1 2 m v2 Potential energy on the other hand is the stored energy The potential energy is the highest when the object is at rest and at rest there is zero kinetic energy since there is no speed involved vice versa A form of potential energy is electrostatic potential energy this comes from the intersection be tween charged particles This the formula to finding this Eel KQ1Q2 d The SI unit for energy is the joule One joule is defined as the amount of energy exerted when a force of one newton is applied over a displacement of one meter A calorie was originally de fined as the amount of energy required to raise the temperature of l g of water from 14 5 C to 15 5 C 1 cal 1000 cal 1 kcal A force is any push or pull exerted on an object W FD Heat is the energy transferred from a hotter object to a colder one There are 4 laws in thermodynamics 1 Zeroth law when three bodies at different temperatures come into contact the equilibrium temperature will be attained by these three bodies 2 Energy can neither created nor destroyed but can change from one form to another 3 Entropy must be positive and always increasing 4 Without the help of any external agency impossible to transfer heat from a low temperature source to high temperature sink These are the key points in the law of thermodynamics In a closed system not necessarily the universe energy is neither created nor destroyed That is energy is conserved In a closed sys tem the entropy of the system does not decrease Internal Energy It is the total energy possessed by the body by virtue of a particular configura tion of it s molecules and also their random motion Thus internal energy is the sum of Potential and kinetic energies of the molecules of the body The change in internal energy is defined as delta E E final E initial Delta E is the sum of the heat added to or liberated from the system delta E Q W Exothermic the word describes a process that releases energy in the form of heat Endothermic a process or reaction that absorbs energy in the form of heat Enthalpy is the amount of heat content used or released in a system at constant pressure En thalpy is usually expressed as the change in enthalpy The change in enthalpy is related to a change in internal energy H E PV The work involved in the expansion or compression of gases is called pressure volume work w P delta V When a change occurs at constant pressure the change in enthalpy delta H is given by the below delta E P delta V qp w w qp Enthalpy of a reaction or energy change of a reaction DH is the amount of energy or heat ab sorbed in a reaction If the energy is required DH is positive and if energy is released the DH is negative delta H H products H reactants 1 2 Enthalpy is an extensive property The enthalpy change for a reaction is equal in magnitude but opposite in sign to delta H for the reverse reaction The enthalpy change for a reaction depends on the states of the reactants and products Calorime try is the science associated with determining the changes in energy of a system by measuring the heat exchanged with the surroundings The heat capacity is the amount of heat required to raise the temperature of the entire calorime ter by 1 K and it is usually determined experimentally before or after the actual measurements of heat of reaction q mc delta T Hess Law states that the heat evolved or absorbed in a chemical process is the same whether the process takes place in one or in several steps This is also known as the law of constant heat summation The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy from the formation of 1 mole of the compound from its constituent elements H rxn H f products minus H f reactants