Rates+of+Reaction

= = =RATES OF REACTIONS= =Collision Theory=
 * The rate of a reaction is the speed at which a reaction occurs.** Some reactions take hundreds, maybe even thousands of years while other can happen in less than one second.

==//__Science ideas of collision theory.__ Chemestry ideas relating to factors which affect the rates of reaction: Increasing the concentration of the acid provides more acid particles, therefore providing more successful collisions each second. As the particles collide more often the rate of reaction is increased, therefore changing the reactant to a product at greater speed.//==

The collision theory says that the more collisions in a system, the more likely combinations of molecules will happen. If there are a higher number of collisions in a system, more combinations of molecules will occur. **The reaction will go faster, and the rate of that reaction will be higher.**

Elements are always combining or breaking down. The reactions happen over and over but not always at the same speed. A few things affect the overall speed of the reaction and the number of collisions that can occur. They are: concentration surface area pressure temperature whats da rest?? lol some one fill it in plz

=Concentration=

**Concentration**: If there is more of a substance in a system, there is a greater chance that molecules will collide and speed up the rate of the reaction. If there is less of something, there will be fewer collisions and the reaction will probably happen at a slower speed.


 * Temperature**: When you raise the temperature of a system, the molecules bounce around a lot more (because they have more energy). When they bounce around more, they are more likely to collide. That fact means they are also more likely to combine. When you lower the temperature, the molecules are slower and collide less. That temperature drop lowers the rate of the reaction.

That greater concentration of molecules increases the number of collisions. When you decrease the pressure, molecules don't hit each other as often. The lower pressure decreases the rate of reaction.
 * Pressure**: Pressure affects the rate of reaction, especially when you look at gases. When you increase the pressure, the molecules have less space in which they can move.


 * Surface** **Area:** the larger the surface area of reactants (Mg+HCl) the more the rate of reaction increases. For Example: Mg Shavings reation rate is greater than the reaction rate of Mg ribbion. This is because collisions (the collision thereoy) are able to happen faster as the particles are able to colide more, compared to if they were locked inside of the Mg Clump.[[image:http://2.bp.blogspot.com/_Wbn-V9TNe4s/SXFKngqEJ2I/AAAAAAAAAAc/8dwGPvz9_yo/s320/sa.gif width="318" height="283" align="right"]]

Visit this site for good revision on chemistry.
 * Most of this was taken from [|chem4kids.com]

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How does it work?
Coke is basically sugar (or diet sweetener), flavoring, water and preservatives. The thing that makes coke bubbly is invisible carbon dioxide gas, which is pumped into bottles at the bottling factory using tons of pressure. Until you open the bottle and pour a glass of coke, the gas mostly stays suspended in the liquid and cannot expand to form more bubbles, which gases naturally do. But there's more... If you shake the bottle and then open it, the gas is released from the protective hold of the water molecules and escapes with a whoosh, taking some of the coke along with it. What other ways can you cause the gas to escape? Just drop something into a glass of coke and notice how bubbles immediately form on the surface of the object. For example, adding salt to coke causes it to foam up because thousands of little bubbles form on the surface of each grain of salt. Many scientists, claim that the Mentos phenomenon is a physical reaction, not a chemical one. Water molecules strongly attract each other, linking together to form a tight mesh around each bubble of carbon dioxide gas in the coke. In order to form a new bubble, or even to expand a bubble that has already formed, water molecules must push away from each other. It takes extra energy to break this "surface tension."  In other words, water "resists" the expansion of bubbles in the coke. When you drop the Mentos into the coke, the gelatin and gum arabic from the dissolving candy break the surface tension. This disrupts the water mesh, so that it takes less work to expand and form new bubbles. Each Mentos candy has thousands of tiny pits all over the surface. These tiny pits are called nucleation sites - perfect places for carbon dioxide bubbles to form. As soon as the Mentos hit the coke, bubbles form all over the surface of the candy. Couple this with the fact that the Mentos are heavy and sink to the bottom of the bottle and you've got a double-whammy. When all this gas is released, it literally pushes all of the liquid up and out of the bottle in an incredible coke blast. You can see a similar effect when cooking potatoes or pasta are lowered into a pot of boiling water. The water will sometimes boil over because organic materials that leach out of the cooking potatoes or pasta disrupt the tight mesh of water molecules at the surface of the water, making it easier for bubbles and foam to form. Why should you use diet Coke or diet Pepsi? The simple answer is that diet coke just works better than regular coke. Some people speculate that it has something to do with the artifical sweetner, but the verdict is still out. More importantly, diet coke does not leave a sticky mess to have to clean up.