Collision Theory

[Freak]

What is the Collision Theory? I need to know how and why :

• Temperature
• Concentration of the acid used
• Catalysts
• Surface area

they affect chemical reactions? Please I need this question answered, because I am doing GCSE coursework.

[moose!]

Try this site - http://www.gcsescience.com/rc1.htm - it looks like it aimed at GCSE level understanding so should help you.

[j2buttonsw]

Well the higher the temperature the more the reactants collide about and the more likely a reaction will occur. Similarly, if a reactant is the acid, the more acid you add the more likely a reaction will occur simply because there is more of it to be able to react. Catalysts aren't involved directly in the reaction (no catalysts are used up or converted like the reactants) but they are able to increase the rate of the reaction. This is often because they can orientate the reactants in such a way the reation is quicker. If you increase the surface area of a solid reactant there is more of it available to be reacted (rather like increasing the concentration of a soluble reactant like the acid).

[Peter Pedant]

Well thats the how: here are some whys

Temperature - The faster atoms may be the ones taking part in a reaction, (activation energy) and so when it is hotter, there are more atoms with the higher energy so the reaction gos faster.

Concentration: Hmmm There are more protons around in a given volume, therefore the chances of a reaction are greater.

I mean its really [H+] is directly proportional to rate, but that is not GCSE level

Catalysts increase reaction rates, but not eauilibrium concentrations. They may orient the atoms. They may also hold the reactants in an activated state for longer, so there is a greater chance of a reaction. This is how enzymes act as catalysts

Surface area - the reaction will only occur on the outside of a crystal. increasing the surface area increases the number of atoms which have a chance to interact.

For catalysts and SA, use decomposition of H202 and manganese dioxide as examples

Good luck, I always found Chemistry interesting - i took the o level as they were then in 1965

[moose!]

Not wanting to upset anyone but I'd be careful where you get your information.  I realise Peter is only trying to help but some of his comments are a little confusing.  You are much better going for a text book or your school notes not a site like this.  I have a Chemistry degree and feel nervous about giving information in case it isn't correct or isn't how something is being currently taught in school (and it was only 10 years since I was there).  As I say, just a warning.

[Lindz]

I hope this helps you with your GCSE coursework:

The collsion theory:
Particles need to collide with each other to react and the collison theory is all about this.The can be affected by the temperature of the particles, the concentration of the particles, whether a calayst is used or the surface area (if the particles are solid).

Temperature affects the rate of a reaction because if particles are cold, they move slowly and there are few collions between them. But when they are heated up they move much faster or you can also say they have more kinetic energy. When the move faster there is more of a chance of a collision. More collions means that the reaction goes faster - its rate increases.

Concentration of the acid used also affects the rate because when there is a higher concentration(more acid) there are more partciles to collide with each other-more collisions means that the reaction goes faster.

A catalyst is a substace that can speed up a chemical reaction without actually being used up in the reaction. It gives the particles a surface to stick to so they can collide with each other there - more collisions. Again when there are more collisions this causes the reaction to go faster.

Surface area also affects the rate of a reaction if the partcicles are solid. Larger particles collide less often because there are fewer of them. So making the particles smaller means that there are more of them to collide with each other meaning that there will be more collisions and a faster reaction.

So all of these factors affect chemical reaction becuse changing them means that the reaction goes faster.

I hope this helps you with you coursework