# Rates of Reactions

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• Created by: Katie
• Created on: 21-05-13 16:58
• Rates of reactions
• Collision Theory
• An explanation of chemical reactions in terms of reacting particles colliding with sufficient energy and the correct orientation for a reaction to take place.
• Activation energy
• The minimum amount of energy needed to start a reaction.
• The affect of concentration
• As you increase the concentrationthe rate is quicker.
• Higher concentration= particles closer together
• It also increases the frequency of collisions so the rate of a reaction increases.
• The graph would like somehing like: the line startig half way up the y axis and then going in a steady diagonal line up.
• Real life example - in limestone when the statues are damages by acid rain. The higher the concentrationof acid in the rain water, the quicker the damage occurs.
• Increasing the concentrationof reactants in solutions increases the frequency of collisions between particles and so it increases the rates of reactions.
• The affect of surface area
• The larger the  surface area, the more frequent collisions will take place, so there is a faster rate.
• Real-life example - When you light a fire, you use small pieces of wood to begin the fire to increase the surface area. This means ther is more wood exposed to react with the oxygen.
• The rate of a chemical reaction increases if the surface area of any solid reactant is incresed. This increases the fequency of collisions between reacting particles.
• The affect  of temperature
• The higher the temperature the greater the kinetic energy of the particles. Therefore, they are more likely to collide. Collisions will have more energy, causing the rate to increase.
• Real-life example - Fridge/freezer slows down the rate of food going off.
• Graph would look like: a stright digonal line going up from the point 0.
• Reactions happen quicker as the temperature increases. Increasing the temperature increases the rate of the reaction because particles collide more frequently and more energetically. More of the collisions result in a reaction because a higher proportion of particles have energy greater than the activatin energy.