 Alright, today the video is going to be on types of reactions. We have five different types of reactions that we want to go over. Just briefly, those five types are your combination reaction, your decomposition reaction, a single replacement reaction, a double replacement reaction, as well as a combustion reaction. So first of all, let's start out with our combination reaction. In a combination reaction, two or more elements, or simple compounds, combine to form one product. So the generic formula for a combination reaction is going to be A plus B yields a product of A, B. In this reaction we're taking two reactants, reactants being the items on the left side of the arrow, and we're combining them to form one product, product on the right side of the arrow. Here's an example of a combination reaction. When we take magnesium solid, and we react it with oxygen from the atmosphere, we yield a solid product called magnesium oxide. So let's do this reaction, and see what happens when magnesium reacts with oxygen. In order to start this reaction, we need a flame, so whenever magnesium reacts with oxygen with the help of a flame, we get a very bright white light, and then the product that is left over is magnesium oxide. The second type of reaction is a decomposition reaction. A decomposition reaction is simply the opposite of a combination reaction. This is where you have one reactant that splits into two or more products. So the generic formula for a decomposition reaction is A, B, which is your compound, is reacting and separating into two or more products. An example of a decomposition reaction is splitting water. Whenever we split water, we get hydrogen gas and oxygen gas. This process is known as electrolysis, the splitting of water using electricity. Our third type of reaction is a single replacement reaction. This is where one element takes the place of a different element in a reacting compound. So the generic formula for a single replacement reaction, plus BC, reacts to form a new product, AC plus B. What you see that's happened here is A and B have simply switched places. An example of this reaction is reacting magnesium metal with hydrochloric acid to form magnesium chloride and hydrogen gas. What you see is happening here is the magnesium and the hydrogen are simply switching places to form a new product. Let's watch what happens whenever we mix magnesium metal and hydrochloric acid. Pay attention to the reaction that takes place as well as looking for that hydrogen gas that's being emitted. So you can see the magnesium is now completely gone. We have a new product called magnesium chloride which is soluble in water and we emitted that hydrogen gas from the reaction. Our fourth type of reaction is known as a double replacement reaction. It's somewhat similar to a single replacement reaction except for the fact that two items from the reaction switch places. So you have two positively charged ions in the reacting compounds which switch places with each other. An example of this type of reaction is taking lead nitrate and mixing it with sodium iodide. And when this occurs you form two new products which are lead iodide and sodium nitrate. But as you can see what is happening here is our positively charged ions and in chemistry positively charged ions come from metals. Metals are found on the left side of the periodic table. Lead and sodium are both metals so these are the positively charged ions. And what you see is happening is the lead and the sodium switch places. They take on each other's negatively charged ion. In this formula or in this double replacement reaction the generic formula is AB plus CD. These are your reactants found on the left side of the arrow react to positively charged ions switch places to form AD and our other product is going to be BC. So let's watch what happens now whenever we mix lead nitrate and sodium iodide. This tube contains lead nitrate a clear colorless transparent liquid. This tube contains sodium iodide also a clear colorless transparent liquid. Let's watch what happens whenever we mix the two together. When lead nitrate and sodium iodide are mixed together we take two aqueous compounds meaning compounds that are soluble in water and we form lead iodide which is a solid substance. So what we have done is we formed a yellow color solid substance which is now floating to the bottom. Our final type of reaction is known as a combustion reaction. In a combustion reaction this is a reaction that we should all be familiar with. In a combustion reaction you have a hydrocarbon, a carbon containing compound which reacts with oxygen in the air to form water, carbon dioxide as well as energy. This reaction we should all be familiar with because whenever we get in our car and start it up this is the reaction that is taking place in our motor. Gasoline is a carbon containing compound. When mixed with oxygen which your car takes in from the atmosphere it reacts to produce water vapor, carbon dioxide and the energy is transferred into moving your car forward.