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ENERGY IN CHEMICAL REACTIONS
•During chemical reactions the particles are rearranged to form new substances.
• The rearrangement of these particles can cause chemical energy to be released or absorbed.
•Types of Energy- heat (thermal), light (radiant), movement (kinetic), stored (potential),sound, electrical.
Chemical Energy is measured in Joules J.
Chemical Energy is stored in the bonds of chemical substances.
This energy comes from:
The law of the conservation of energy states that energy cannot be created or destroyed, it can only be transformed from one type of energy to another.
•The total chemical energy of the products of the chemical reaction is less than the total chemical energy of the reactants.
•The excess energy is released to the surroundings.
•Heat is given off.
CH4 (g) + O2 (g) --> CO2 (g) + H2O (g) + energy
•The total chemical energy of the products of the chemical reaction is greater than the total chemical energy of the reactants.
•Energy is absorbed from the surroundings.
•Energy enters the reactions system- will feel cold.
CaCO3 (s) + energy--> CaO (s) + CO2 (g)
Changes of state
Changes of state are physical changes- these require either the release or absorption of energy for the change to take place.