[Music] hi and welcome back to three size lessons Cole you K by the end of this video you should be able to describe the effective temperature on the rate of a chemical reaction remember that collision Theory helps us to explain reaction rates collision theory states that chemical reaction can only take place when the reacting particles collide with each other and the collisions must have sufficient energy the rate of the reaction is determined by the frequency of successful collisions in other words the number of collisions per second now there's something important about this definition that we need to look up more closely as we said the particles must collide with sufficient energy so what does this actually mean in a previous video we looked at energy in chemical reactions I'm showing you here the energy profile for a reaction as you can see the product has less energy than the reactants started with this tells us that the reaction is exothermic that's because energy must have been released from the reaction to the surroundings now you'll notice that the energy actually increases before the reaction completes and I'm showing that here we call this the activation energy the activation energy is the minimum amount of energy that the particles must have in order to react in other words to collide successfully activation energy is a key idea in chemistry and we're going to look at it later in the video on catalysts take a look at this diagram this shows particles taking part in a chemical reaction the size of the arrow shows us the energy of each particle as you can see some particles have more energy than others imagine that two particles with only a small amount of energy collide for example of these two because they have a low energy they cannot overcome the activation energy barrier in that case they would not collide successfully and no reaction would occur however imagine that two particles with a large amount of energy collide such as these two now they've got enough energy to overcome the activation energy barrier and collide successfully in this case a reaction would take place and we can see that here so what would happen if I increase the temperature increasing the temperature increases the rate of chemical reactions but because increasing the temperature increases the energy of the particles like this because the particles now have more energy they now move faster this increases the frequency of collisions in other words there's a greater number of collisions per second secondly each collision now has more energy that means that more particles can overcome the activation energy barrier and collide successfully so because the rate of reaction increases with temperature we can say that the rate of reaction is proportional to the temperature remember you'll find plenty of questions on the effect of temperature on the rate of reaction in my vision workbook and you can get that by clicking on the link above ok so hopefully now you should be able to describe the effect of temperature on the rate of a chemical reaction [Music]