Endothermic and Exothermic reactions

Topics: Water, Energy, Thermodynamics Pages: 2 (446 words) Published: August 17, 2014
Grade 11 Research task: Chemistry
Endothermic and Exothermic reactions
A chemical reaction is a process in which one or more substances are chemically changed into one or more new substances. A chemical reaction may involve the motion of electrons in the forming and breaking of chemical bonds. Therefore when a chemical reaction takes place, energy is transferred to, or from, the environment. A Chemical reaction can either be exothermic or endothermic. Exothermic Reactions

During an Exothermic Reaction a transfer of energy to the surrounding, usually in the form of heat, takes place. This causes an increase in the temperature of the surrounding environment. The process can be easily explained using the change of phases of Water (H2O): Liquid water had to have energy put into it to become steam, and that energy is not lost. Instead, it is retained by the gaseous water molecules. When these molecules condense to form liquid water again, the energy put into the system must be released. And this stored energy is let out as exothermic heat. The same explanation can be used for the process of freezing: energy is put into a liquid during melting, so freezing the liquid into a solid again returns that energy to the surroundings. The most stable state is where all energy has been released. When going to a more stable state, energy will be released. On an enthalpy level diagram, higher positions will be less stable therefore, if the product is lower, heat is released. Therefore we can say that the formation of bonds causes an energy release (exothermic). Examples of exothermic reactions:

making ice cubes
formation of snow in clouds
condensation of rain from water vapour
a candle flame
rusting iron
burning sugar
forming ion pairs
Combining atoms to make a molecule in the gas phase
mixing water and strong acids
Endothermic Reactions
An Endothermic reaction is a reaction that takes place when energy is taken in from the surrounding environment. This energy is...
Continue Reading

Please join StudyMode to read the full document

You May Also Find These Documents Helpful

  • Exothermic and Endothermic Reactions Essay
  • Exothermic Reaction Essay
  • Endothermic and Exothermic Reaction Essay
  • Endothermic and Exothermic Reactions Essay
  • Thermochemistry: Temperature and Endothermic Reaction Essay
  • Ice Packs an Endothermic Reaction Essay
  • Exothermic vs Endothermic Reactions Worksheet Essay
  • Essay on Endothermic and exothermic reactions

Become a StudyMode Member

Sign Up - It's Free