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in chemistry will be studying tons of different reactions that can be organized into different classes of reactions. So in this video, all we covering combination anti composition reactions, so the first type of reaction that I'll be going over are called combination reactions and combination reactions are reactions where you make one single product from a number of different reactions having at least two or more eso for a generic kind of reaction. You have something like molecule a plus molecule B combines to make molecules. And again, this is a combination reaction because you are combining one. You are combining two or more reactant in this case, molecule A and molecule B to create one single product on. In this case, it is molecules. So in nature, um, something you might be more familiar with is erection to make water, so it's make water. You can combine oxygen gas with hydrogen gas, um, two great water, which is a liquid in room temperature. And whenever you're running a chemical reaction, you want to make sure that you write out the molecular formula, which is composed of atoms that are whole and not fractions of an atom. A swell as the states. So in this case, at room temperature, um, auction exists as a gas. Hydrogen exists as a gas and liquid water exists as a liquid. And and whenever you write your actions, you also want to make sure that they are balanced. So right now, the reaction as is, is not balanced. So we need to go back and adjust this chemical formula so that the number of oxygen atoms on the left side are equal to that of the right side. And the number of hydrogen on the left side is equal to the number on the right side. Eso to start. Let's work with the number of hydrogen, so you can see that as of now there are two hydrogen atoms on left side and two hydrogen atoms on the right side. So we're fine, Aziz. Enough. But if we look at the number of oxygen atoms, there are two on the left side and two on the right side. Eso. We need to have at least two moles on the right side to make sure that the number of oxygen's are correct. But when we do this, but now we have more hydrogen atoms on the right side than the left side eso To get the same number of hydrogen atoms on the left side, we also need a coefficient of to next to the molecule. And so now we can see that the equation is balanced because we have the same number of oxygen atoms and hydrogen atoms on the left side and the right side. So in some, this is basically what a combination reaction is. Uh, so you want to make sure that you have a single product? Uh huh. As the end result of a reaction with two or more reactive. So before I go into decomposition reactions, which can be thought of as the opposite of a combination reaction, I wanted to mention a very specific case on DSO. If you have a case where you have one reactant um, making a new molecule well, you have something called isomerization, and this is not well illustrated using chemical formulas, because chemical formulas actually don't tell you anything about the bonding. So in this case, I will be introducing line structures, um, which might be a little intimidating, but you'll learn more about them later on in the course. Eso For example, let's say you have something, Um, like a carbon chain, Um, like butane and butane has a carbon chain off four carbons. And for the purpose of this, I won't be including the higher regions. But just know that if the carbon is not bonded to another carbon, all the other bonds, um, are bonds with hydrogen atoms and for carbon will make four bonds. Um, so let's say you have a carbon chain that looks like this if it under grows and ice harmonization, Um, the chemical formula stays the same, but the bonding of the molecule is different. So here you can see that first we begin with a chain, and now we have something different. And so this is an example of a nice authorization. So you have one reactant turning into one product. Now the next type of reaction that will be learning is called a decomposition reaction. So for decomposition reactions, this can be thought of as the opposite of a combination reaction. So for 80 composition reaction, you start off with one reactant, which will decompose into two or more products. So if we compare this to the combination reaction from the floor, we see that it is the reverse. So if you start out with a reacting see, it can decompose to create two products, which are molecules A and molecule B. And if we apply the same analogy with the one from before, you could have water decomposing back to oxygen gas as well as hydrogen gas. The only issue is that in nature that's actually does not happen. Um, because obviously our oceans are made up of water, and it would be a terrifying thought to think that our own ocean can disappear and just create oxygen and hydrogen. And and so, just for the purpose of illustrating my point, we can see that the decomposition reaction is the opposite of the combination reaction, where instead of making one product from multiple reactions, you have one reacted creating multiple products. And so even though this doesn't happen in nature, something that does happen in nature is the decomposition of hydrogen peroxide. Eso hydrogen peroxide is H 202 and this can create hydrogen gas and oxygen. Guess so. The decomposition of water technically does not happen in your life because of energetic, but something like this we can definitely happen. So basically of our combination reactions, you have two or more reactant to make one product price authorization. You make a single product from one reacted, and for decomposition reactions, you make multiple products from a single reactive.