Energy changes Flashcards
Chemical reactions can only occur when…
… reacting particles collide with each other with sufficient energy.
What is the activation energy?
The minimum amount of energy that particles must have to react.
In terms of bond energy, explain an exothermic reaction.
In an exothermic reaction, the energy released from forming new
bonds is greater than the energy needed to break existing bonds.
In terms of bond energy, explain an endothermic reaction.
In an endothermic reaction, the energy needed from forming new
bonds is greater than the energy released to break existing bonds.
What are the 2 stipulants of a chemical reaction?
> energy must be supplied to break bonds in the reactants
energy is released when bonds in the products are formed.
What is the overall energy change of the reaction?
The difference between the sum of the energy needed to break
bonds in the reactants and the sum of the energy released when
bonds in the products are formed
What happens to energy in a chemical reaction?
It is conserved.
The amount of energy in
the universe at the end of a chemical reaction…
is the same as before the reaction took place.
What is an exothermic reaction?
An exothermic reaction is one that transfers energy to the
surroundings so the temperature of the surroundings increases.
What are examples of exothermic reactions?
Exothermic reactions include combustion, many oxidation reactions and neutralisation.
What are everyday uses of exothermic reactions?
Self-heating cans
and hand warmers
What are endothermic reactions?
An endothermic reaction is one that takes in energy from the
surroundings so the temperature of the surroundings decreases.
What are examples of endothermic reactions?
Thermal decompositions and the
reaction of citric acid and sodium hydrogencarbonate. Some sports
injury packs are based on endothermic reactions.
What do cells contain?
Chemicals which react to produce electricity.
How to make a simple cell?
> Two different electrodes with an electrolyte.
The electrolyte is a liquid that contains ions which react with the electrodes
The chemical reaction sets up a charge difference between the electrodes.
if connected by a wire, the charge is able to flow and electricity is produced.
