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EXOTHERMIC AND ENDOTHERMIC REACTIONS - Coggle Diagram
EXOTHERMIC AND ENDOTHERMIC REACTIONS
REACTION PROFILES SHOW ENERGY CHANGES
This reaction profile shows an exothermic reaction- the products are at a lower energy than the reactants.
The difference in height represents the overall energy change in the reaction (the energy given out) per mole.
The initial rise in the line represents the energy needed to break the old bonds and start the reaction. this is the activation energy
The activation energy is the minimum amount of energy the reactants need to collide with each other and react.
The greater the activation energy, the more energy needed to start the reaction- this has to be supplied, ( example, heating the reaction mixture)
Reaction profiles are diagrams that show the relative energies of the reactants and products in a reaction, and how energy changes over the course of the reactions
ENERGY MUST ALWAYS BE SUPPLIED TO BREAK BONDS
In endothermic reactions the energy used to break the bonds is greater than the energy released by forming them
Energy is released when new bonds are formed - so the bond is an exothermic process
During a chemical reaction, old bonds are broken and new bonds are formed
Energy must be supplied to break existing bonds- so bond breaking is an endothermic process
In exothermic reactions, the energy released by forming bonds is greater than the energy used to break them.
ENERGY IS MOVED AROUND IN CHEMICAL REACTIONS
Chemicals store a certain amount of energy-and different chemicals store different amounts
if the products of a reaction store more energy than the original reactants then they must have taken in the difference in energy between the products and the reactants from the surroundings during the reactions
but if they store less, then the excess energy was transferred to the surroundings during the reaction
the overall amount of energy doesn't change. this is because energy is conserved in reactions - it cant be created or destroyed, only moved around. this means the amount of energy in the universe always stays the same
ENDOTHERMIC REACTIONS
AN ENDOTHERMIC REACTION, HEAT IS TAKEN IN
AN ENDOTHERMIC REACTION IS ONE WHICH TAKES IN ENERGY FROM THE SURROUNDINGS. THIS IS SHOWN BY A FALL IN TEMPERATURE
ENDOTHERMIC REACTIONS ARE MUCH LESS COMMON THAN EXOTHERMIC REACTIONS BUT THEY INCLUDE:
THE REACTION BETWEEN CITRIC ACID AND SODIUM HYDROGENCARBONATE
THERMAL DECOMPOSITION SUCH AS HEATING CALCIUM CARBONATE CAUSES IT TO DECOMPOSE INTO CALCIUM OXIDE ALSO KNOWN AS QUICKLIME AND CARBON DIOXIDE.
IN AN EXOTHERMIC REACTION, HEAT IS GIVEN OUT
AN EXOTHERMIC REACTION,IS ONE WHICH TRANSFERS ENERGY TO THE SURROUNDINGS USUALLY BY HEATING. THIS IS SHOWN BY A RISE IN TEMPERATURE
An example of exothermic reaction would be burning fuels which is also known as combustion.
this gives out a lot of energy it is very exothermic.
neutralisation reactions (acid + alkali) are also exothermic
many oxidation reactions are exothermic. adding sodium to water releases energy, so it must be exothermic. the reaction releases energy and the sodium moves about on the surface of the water as it is oxidised
EXOTHERMIC REACTIONS HAVE LOTS OF EVERYDAY USES
HAND WARMERS
the exothermic oxidation of iron in the air, with a salt solution catalyst to release energy
SELF HEATING CANS
hot chocolate and coffee rely on exothermic reactions between chemicals in their bases
