gcsescience.com 24 gcsescience.com
Rates of Reaction
Energy - Exothermic and Endothermic.
What do Exothermic and Endothermic mean?
A chemical reaction always has a change in energy.
In a reaction going from reactants to products, either
1) heat is
given out - called exothermic
2) heat is taken in - called endothermic.
The large majority of chemical reactions are exothermic.
Exothermic reactions give out heat to their surroundings.
Some physical processes are associated with a
energy. For example, melting and boiling are endothermic
but freezing and condensing are exothermic.
bonds (overcoming the force of
requires energy. You have to put heat in - it is endothermic.
This is why melting and boiling are endothermic.
energy - it is exothermic.
This is why freezing and condensing are exothermic.
In a chemical
reaction you need to put energy in
to break the bonds that exist in the reactants. You
get energy out when new bonds are formed to
make the products. The bonds are covalent or ionic.
If you get
out more energy than you have
to put in,
then overall the reaction is exothermic.
This is what normally occurs - see some examples.
If you have to put in more energy
than you get out,
then the reaction is endothermic - see some examples.
Links Catalysts and Energy Enzymes Revision Questions
gcsescience.com The Periodic Table Index Energy Quiz gcsescience.com
Home GCSE Chemistry GCSE Physics
Copyright © 2015 gcsescience.com. All Rights Reserved.