How does concentration affect the rate of a chemical reactions?
Concentration is how much there is dissolved in a volume of solvent. For reactions that take place in solution, the greater the concentration of reactants, the greater the rate of the reaction, as the chances of collisions increases the more there are reactants in a given volume. If the concentration of a chemical increases, there will be more particles within a given space. Particles with therefore collide more often. As concentration, the rate of reaction also increases. In order for a chemical reaction to occur the particles must collide. As you see in the picture below a low concentration has few collisions and a high concentration has more collisions.
"Chemical Rates." http://www.physchem.co.za. N.p., n.d. Web. 10 Mar. 2010. <http://www.physchem.co.za/OB12-che/rates.htm#collision>.
Concen.jpg

Molecular-collisions.jpg
http://www.kentchemistry.com/. N.p., n.d. Web. 5 Mar. 2010. <http://www.kentchemistry.com/images/links/Kinetics/Molecular-collisions.jpg>.