Energy changes Flashcards
How is energy transferred to or from its surroundings during a chemical reaction?
Energy is transferred when bonds are broken or are formed.
What are exothermic reactions?
When energy is transferred to the surroundings, this is called an exothermic reaction, and the temperature of the surroundings increases. (HEAT/HOT/TEMP INCREASES)
E.g. combustion, hand warmers
What are endothermic reactions?
When energy is taken in from the surroundings, this is called an endothermic reaction and the temperature of the surroundings decreases.
(COLD)
E.g. melting ice cubes
What is the collision theory?
Collision theory states that for a chemical reaction to occur, the reacting particles must collide with one another.
What is activation energy?
The minimum kinetic energy required for a reaction to occur is called the activation energy.
Exothermic graphs:
Energy of reactants (first line) is higher than the energy of the reactants (second line).
Endothermic graphs:
Energy of reactants (first line) is lower than the energy of the reactants (second line).
Where is the activation energy on the graph?
It is the difference between the energy of the reactants and the highest peak of the arc.
Where is the overall energy change on the graph?
The difference between the energy of the reactants and products.
How do you calculate the energy change in exothermic and endothermic reactions?
Energy change = energy in - energy out
If the answer is negative it is an exothermic reaction.
