The next is the study of how fast reactions go. Reactions can be slow like the conversion concrete into limestone can take centuries. The resting of steel structures can take decades. Reaction could be a fraction of a second or seconds. Explosions definitely a fraction of a second. So we can have a wide range of how fast reactions go. You measure our reactions by change of concentration of time. Generally, you would like to use mobility. So change of mobility over time for our rate. And we'll play with this a little bit between the different reactants and different products and reactions. Using this stoichiometric ratio. But to get a single rate for all the reactions, reactants and products in the soon reaction. What we do is, for reactant, we do the negative of the change over time or the change of time. And we divide by the coefficient of that reaction. So, the change of reaction would be negative. So this negative is making it possible. We always like our rates being positive. For products where change of concentration is possible, we're doing change of concentration over change of time. And divided by this coefficient. So, it's divided by the coefficient that is making all the different reactants and products being the same. We're doing negative of the change of reactants. So we end up with a positive rate. And positive change of reactants for products. So what effects of rate? How do we affect it? One of the obvious things is that concentration. So concentration affects the rate. We'll see that in the types of rate laws that we're expecting. Temperature affects rate. So the oxidational iron is doing a slow process. But if we give the iron lot of surface here, or you make it into a powder, it's a person's air, so it's well mixed with oxygen. So we throw a handful of iron filings above a campfire. And then it has to flame the campfire, the iron burns real fast. So what is that flame raising the temperature high enough? I guess that fire would go. So it's throwing the iron into the air. It won't start to fire. But if we raise the temperature up, then we can burn that iron. Candles are very important. We use them in all types of chemical synthesis industries. And our environmental processes, like our car, we have catalytic converters to clean up the combustion process. Make the combustion more complete, so we're getting carbon dioxide and water out of it. Instead of carbon monoxide and poly aromatic hydrocarbons, or products of income-peak combustion. So calis, speed of reaction, but they don't get consumed. Another reaction, but their presence helps speed up the reaction. Usually by making up, providing another alternative reaction pathway. A compound that went slow reaction down is called the inhibitor. And we look for inhibitors as many as for a treating set type of illnesses in our body. We try to slow down certain reactions, so we have a better health permit. So for a generic reaction, A plus B gives us C plus D, with coefficients of A, lowercase A for A, lowercase B for B, lowercase C for C, lowercase B for C, lowercase B. We expect our rate law to be written on their reactants. We generally do not expect to see any products or other things in there. We do, a catalyst will show up as a term, we know it's not a reactant. So we expect our rate law to be rate equals a constant, the rate constant times the first reaction to an exponent times a second reaction to an exponent. We'll continue for reaction to an exponent. The exponents we cannot predict, they are not the coefficients from the balance equation. And we cannot predict them based on the balance equation at all. So the only way that we could predict this, if we knew all the elementary steps of the reaction, then we could derive a rate law. But generally, the overall reaction could have multiple steps within it. So our rate laws rate equals constant times each reactant to an exponent. The rate constant is tetrapendent, so we don't see temperature in the equation. But we're going to have another equation to derive K and show it's temperature dependence. The, if we're just looking at A, so what's the order of reaction with respect to A? The order is that exponent. So if the exponent is zero, it's zero order. If one is first order, it's two and second order. We could have fractional orders. We're not going to be focusing on those. And the overall order of the reaction is some of the lolly exponents in the rate law. So if we had an x was one, y was two, and we have one plus two, the overall order is three, or our third order reaction. So this is an intro to it. We'll next play with a story concrete between the various reactants and various products. And then go into the rate laws better using an integrated rate laws that allow us to do better process. So let me actually write down the rate laws. So this is zero order. If I'm just going to do the A on A, so rate equals, if it's A to a zero, that disappears. So rate equals K, a constant. So for zero order reaction, the rate is constant. Well, for a first order reaction rate is directly proportional to the concentration. So if we double the concentration, we double the rate. For a second order reaction. Now the rate is proportional to the square of the concentration. So if we double the concentration to square, we're going to quadruple the rate to the rate increases way faster for a second order reaction as we increase the concentration. So this is a little intro. Again, we'll go into these by doing an integrated rate law, which allows us to take data and figure out the order of the reaction better. So we're going to have two methods of figure out the order reaction. One is by using integrated rate laws and plotting graphs. And the second one is using a method of initial concentration. For when we double a concentration, what's happened? We don't look concentration here, but we know change in rate. Double a concentration here, we're doubling the rate. Double a concentration here, we're quadrupling the rate. So that would be a method of initial rates to figure out the rate law on that one.