topic 5 Flashcards
What does it mean 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 reactants from the surroundings during the reaction
Why does the overall energy not change in the reactions
Because energy is conserved
What does it mean if the reaction stores less energy
Then the excess energy was transferred to the surroundings
What is an EXOTHERMIC reaction
One which transfers energy to the surroundings usually by heating
How can you tell a reaction is exothermic
It is shown by a raise in temp
An example of an exothermic reaction
Combustion
What is an endothermic reaction
One which takes in energy from the surroundings
How can you tell a reaction is endothermic
It is shown by a fall in temp
2 examples of endothermic reaction
- thermal decomposition
- reaction between citric acid and sodium hydrogen carbonate
What happens to bonds in a chemical reaction
Old bonds are broken and new bonds are formed
What must happen to energy to break existing bonds
It has to be supplied
What process is bond breaking
Endothermic reaction
What happens to energy when new bonds are formed
Energy is supplied
What process is bond FORMATION
An exothermic reaction
In exothermic reactions the energy released by forming binds is …
Greater than the energy used to break them
