Description: This passage is mainly about what is activation energy. In this passage, the writer makes us understand how reactions work and shows us the test of it step by step.
Welcome to a lecture online and now in order to understand how reactions work, let’s talk a little bit about the activation energy, so the assumption is when we put reactants together, that reaction will normally take place but that’s not always the case, because there’s a certain amount of bound string between the molecules in the reactants.
So before they can start reacting form different molecules, we have to break those bonds, so that means that enough kinetic energy has to come into the reaction to vibrate or break the bond sufficiently for the reaction to take place, so what happens sometimes is that you bring two reactants together and nothing happens, because you first have to give enough energy to the reactants so that they can break the bond sufficiently for the next reaction to take place.
For the the product, it should not be reactants but this should be for the products to form, now it can be that, the amount of energy released in that reaction is a way more than what you need to get the reaction going and the amount of energy that you need, it’s getting a ball over the hump, for example you kick a soccer ball and you get to get over the hump, you have to kick it hard enough to get over there.
Once you get past the hump, then the ball will roll down to a lower energy level and that’s what an exothermic reaction is, it gives off energy but it requires a little bit of energy in order to get the reaction started, and without that additional energy the reaction will never take place, so that’s what we mean by the activation energy.
There are quite a few reactions that require that energy, even though a sufficient amount is released more than payback for the energy needed to get the reaction going, in some cases the reaction is not exothermic, it is endothermic, in other words you still need to provide activation energy, but you need to provide so much activation energy to get the reaction going that.
The energy that you get from making the products is less than what it takes to activate the reaction or to get the reaction going, therefore that energy typically comes within the products from the reactants, therefore the temperature may go down from the solution based upon this situation where the amount of energy you put back into the system is less than the amount.
It takes to get the reaction going, so you can probably measure a decrease in temperature, because the energy has to come from somewhere, and in this case you probably measure an increase in temperature, because more energy is released in both cases, the situation is that you need some energy to get the reaction going, and it’s all about what these molecules are made out of.
We’ll see some examples of that for me to solidify this concept, but it’s interesting because normally you expect that you put two reactants together and immediately something happens, it may not happen in less than sufficient energy which is available to get the reaction going, so the speed at which the reaction takes place a lot has to do with how much activation energy that you’re required to have the reaction take place.