[Alison]

Alison asked the Naked Scientists:
   
Are most reactions exothermic? If so why do we use the bunsen so much in the lab?

What do you think?

[Bored chemist]

All reactions are exothermic- in one direction. They are exactly as endothermic in the other direction.
One reason for heating things up in the lab is to get things to react more quickly.

[lightarrow]

All reactions are exothermic- in one direction. They are exactly as endothermic in the other direction.
One reason for heating things up in the lab is to get things to react more quickly.

...which has not only to do with the enthalpy variation in the reaction, but with lowering the activation energy too.

[Horseradish_5000]

most reaction are exothermic and the bunsen is used to reach the activation energy so it can start.

[lightarrow]

Anyway, many common reactions are endothermic: fusion, vaporization, sublimation, for example.

[Bored chemist]

It's a moot point if phase changes are "reations".


An important reason why some reactios run a lot faster when heated is that one of the reactants melts. Two solids can only react at the points where they are in contact. If you heat them and one melts then it can flow over the other and so there's more contact area.