Endothermic/exothermic Reaction -- by Ria Park

All chemical reactions make changes in energy. Those are:

  Endothermic Reaction:

• This reaction absorbs energy.
• e.g. one ice pack melts. -> it absorbs energy so that ice becomes water.
• It takes more energy to break bonds.

  Exothermic Reaction:

• This reaction release energy.
• 2 explosion explode. -> it release energy.
• It takes takes less energy to break bonds.

> Chemical bonds hold molecules together.

• add energy to break bonds
• lose energy to to join together again.

> Enthalpy(H) is the heat contained in the reactions.

http://www.youtube.com/watch?v=1B3bb9d3WOk