quinta-feira, 23 de janeiro de 2014

Thermochemical Changes - Intro

Energy

The scientific definition of energy describes it as the ability to do work. Without energy, no reactions could occur, therefore, our lives would be impossible to continue. ALL ENERGY ORIGINATES FROM THE SUN! 
In this unit we will study the two types of energy that are extremely related to chemical changes and reactions: Kinetic and Potential Energy.

1) Kinetic:
It is an energy that is related to movement,  and in the case of chemistry, we will be talking about the movement of particles and molecules. Therefore, we will understand that when particles, or molecules, are moving faster, their kinetic energy is increasing. When moving slower, their kinetic energy will decrease. 
Kinetic Energy is very related to temperature. When a substance increases its temperature, it means that the particles are moving fast, therefore, we must have a large kinetic energy. The opposite occurs, when the temperature of a substance decreases.
As we know from previous studies, temperature gives us clues of heat. What is heat? Heat is the transfer of thermal energy between two substance or objects. 

2) Potential:
This energy is related to the bonds of molecules in a substance, when they are formed or broken down, potential energy is changed. In this units, we will focus on the potential energy in the intra molecular bonds, which are of course the bonds between atoms that form a molecule. When this bonds are broken down, or formed, that means that a chemical change, or we can say, a chemical reaction is occurring. 
There are two types of chemical reactions: Endothermic and Exothermic Reactions. 
Endothermic reactions are chemical reaction which energy is required in other to occur. The best example of endothermic reaction is PHOTOSYNTHESIS. Exothermic reaction in another hand is the chemical reaction that releases energy. The best example of exothermic reaction is CELLULAR RESPIRATION. 

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