C6 Energy changes in chemical reactions Flashcards
What is an exothermic reaction?
An exothermic reaction is when thermal energy is transferred to the surroundings so the temperature of the surroundings increases.
What is an endothermic reaction?
An endothermic reaction is when thermal energy is taken in from the surroundings so the temperature of the surroundings decreases.
Why do chemical reactions occur?
Chemical reactions occur so that elements can achieve a more stable energy state by gaining a full outer shell of electrons. - done by chemical bonding.
How is energy transferred in an exothermic reaction?
In an exothermic reaction, the energy is transferred from the chemical energy store of the chemical system to the surroundings and so the energy of the system falls. This means the energy change is negative.
What is the overall transfer in an exothermic reaction?
In an exothermic reaction, the overall transfer is from the system to the surroundings.
What are examples of exothermic reactions?
Examples of exothermic reactions include:
Neutralisation, combustion and oxidation.
How is energy transferred in an endothermic reaction?
In an endothermic reaction, energy is transferred to the chemical energy store of the chemical system from the surroundings and so the energy of the system increases. This means the energy change is positive.
What is the overall transfer in an endothermic reaction?
In an endothermic reaction, the overall transfer is from the surroundings to the system.
What are examples of endothermic reactions?
Examples of endothermic reactions include:
Electrolysis, thermal decomposition reactions and the first stages of photosynthesis.
What type of reaction is bond breaking?
Bond breaking is an endothermic reaction because it requires energy.
What type of reaction is bond making?
Bond making is an exothermic reaction because it releases energy.
