now we're going to think about some related kind of terms so thermal energy is some sort of kinetic energy due to the motion of atoms or molecules so how fast are things moving around temperature on the other hand is a quantitative measure of of how hot or cold something is so i like to think about this in this kind of a diagram down here is that a hot liquid will have a higher temperature and the reason it has a higher temperature is because all the atoms in there are moving faster and faster and then when you cool it down the atoms start moving a lot slower so that is the difference between temperature and thermal energy is thinking about how what happens in a hot liquid versus a cold liquid so how fast are the things that are moving around heat is what we're going to be really concerned about and we're going to call this q and this is the transfer of thermal energy so we can have different kind of transfers that happens from something going from hot to something going colder so remember when things get warmer all the atoms inside are actually vibrating a little bit faster are moving around a little bit faster so this can happen in a solid liquid or a gas so in terms of chemistry what we're really going to look at is our reactions and how they produce heat and we'll give this heat uh term a name uh later so we can think about it exothermic reaction and an exothermic reaction releases heat so you can think about this as an a going to b and heat is on the product side and we can feel this heat that's coming off it'll feel hot to us an endothermic it's a reaction that absorbs heat so our reactant actually requires some heat to it and something like this an endothermic reaction will feel cold because it's actually sucking the heat out of our hand into the reaction itself so some examples of an exothermic reaction are things like combustion kind of reactions so this is when we burn something so if you take an acetylene oxygen torch and you burn it you end up getting heat out and that's how we do a lot of our welding and cutting for the the steel and metals industry and something that's endothermic that you might be familiar with if you've ever gotten hurt doing some activity you might have gotten an ice pack and uh and in these kinds of reactions we are going to take something like ammonium nitrate and that ends up dissolving in the water so you have to smash it so that you can break out the water and mix it with the ammonium nitrate and as it dissolves it absorbs heat so it feels cold to you