TERMS IN THERMOCHEMISTRY WITH THEIR MEANING

·       This article contains terms used in thermochemistry and their meaning. terms like enthalpy, entropy, system, intrisive variables, extrisive variables, exothermic and endothermic etc.
         
          
          HEAT: This is the transfer of energy from a warmer body to a cooler one, heat is transferred because of temperature difference, but remember temperature is not a measure of energy. It just reflects the motion of particles.

·         TEMPERATURE (T): This is defined as the degree of hotness or coldness of a body or object. It is proportional to average kinetic energy of the molecules.

·         ENTHALPY(H): This is the heat content in a substance. Heat exchange at constant pressure when two systems are in contact.

·         ENTHALPY OF REACTION(H_rxn): This is the amount of heat released(negative value) or absorbed(positive value) by a chemical reaction at constant pressure in KJ/mol.

·         ENTHALPY OF COMBUSTION(H_comb): This is the amount of heat released or absorbed when one gram of a substance is burnt in oxygen. Note that combustion reactions yields oxides of that which is combusted.

·         ENTHALPY OF FORMATION(H_f): This the amount of heat absorbed or released when one mole of compound is formed from elements in their standard states in kj/mol.

·         ENTHALPY OF FUSION (H_fus): Heat absorbed to melt one mole of solid to liquid at the melting point, expressed in kj/mol.

·         ENTHALPY OF VAPOURIZATION (H_vap)): Heat absorbed to vapourize or boil one mole of liquid to vapour at the boiling point, in kj/mol.

·         SYSTEM: This is the area of the universe we are focusing on (i.e., the experiment).

·         CLOSED SYSTEM: This system allows the exchange of heat with the surroundings, but does not allow exchange of matter.

·         OPEN SYSTEM: Allows the exchange of both heat and matter with its surroundings.

·         ISOLATED SYSTEM: Allows the exchange of neither heat nor matter with the surroundings.

·         STATE FUNCTION: Is a property that depends only on the current state of the system not on the way in which the system acquires that state. Pressure,  temperature, volume, internal energy, enthalpy and entropy are examples of state functions.

·         INTENSIVE VARIABLES: This is a bulk property that do not depends on the amount of material in the system. Examples are temperature, refractive index, density and hardness of an object. Othe examples include; specific heat capacity, pressure, viscosity, elasticity, melting point, boiling point.

·     EXTENSIVE VARIABLES: This property depends on the amount of material in the system. Examples include mass, volume, enthalpy, entropy, gibb’s free energy, length etc.

·         SURROUNDINGS: this is everything outside the system.

·         ENDOTHERMIC: This involves the absorption of heat from the surroundings. Click Here to get more understanding on endothermic reaction.

·         EXOTHERMIC: This involves the amount of heat released to the surroundings. Click Here to explore more on exothermic reaction.

·         ENTROPY(S): This measures the degree of disorderliness or randomness of a system.

·         GIBB'S FREE ENERGY: This is the amount of useful energy needed to do work.

·         THERMODYNAMICS: This is the study of energy and its interconversions.

·         WORK: This is the force acting over a particular distance. 

       It is expressed as W= -PV.