Addition reactions in organic chemistry

Hydrocarbons and addition reactions:

http://www.starscience.net/chemistryBG/organic2_e.htm

http://www.starscience.net/chemistryBG/hydrocarbons.htm

Properties of ethene:

http://www.tutorvista.com/content/chemistry/chemistry-iii/hydrocarbons/ethene-animation.php