Why does a chemical reaction slow down on cooling

2 Why does a chemical reaction slow down on cooling  

There are two reasons why a chemical reaction slows on cooling first, for particles to react with each other, they have to collide. The lower the temperature, the slower the particles are moving. The slower they move, the less often they collide and the less energy the particles possess, so the slower the reaction goes. Second, for any chemical reaction to work, the old bonds in the reagent molecules have to be broken before new bonds can be formed to give the new products. Consider the simple chemical reaction 

When hydrogen reacts with oxygen to form water, what happens is this  

Step 2 - the energy of the collision causes the bonds of some of the hydrogen and oxygen molecules to break, forming hydrogen atoms. We call these free radicals. 

The asterisk shows that this is an atom and has free un-bonded electrons. Here one hydrogen molecule splits up to give two hydrogen atoms. 

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WHY DOES A CHEMICAL REACTION SLOW DOWN ON COOLING ... 

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