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Combustion Reactions - Concept

Teacher/Instructor Kendal Orenstein
Kendal Orenstein

Rutger's University
M.Ed., Columbia Teachers College

Kendal founded an academic coaching company in Washington D.C. and teaches in local area schools. In her spare time she loves to explore new places.

A combustion reaction (commonly known as burning ) is an exothermic reaction in which something reacts with oxygen. The combustion of organic compounds usually takes the form organic compound + oxygen => water + carbon dioxide.

Alright so we're going to talk about combustion reactions. Combustion reactions are when oxygen combines with a substance and releases energy in the form of light and heat. Combustion reactions are the classic one of the very most exothermic reaction we can have. Exothermic indicating that it releases energy in the form of light and heat that means exothermic. So let's look at this reaction, alright so we have hydrogen combining with oxygen to form water. Now that fact that it's combining with oxygen is our indicator that this is a combustion reaction. But then we also look at it and say it only gives us one product. We can also say this is oh also a synthesis reaction, so this reaction actually falls under two different types of categories. Combustion and synthesis, like typically you'll see a combustion reaction with a hydrocarbon reacting with oxygen rather than other things. What is a hydrocarbon? Well a hydrocarbon is the compound, it's a carbon containing compound with hydrogens or oxygens attached to it.

Let's look at this one below, so we have methane of CH4 reacts with oxygen which is our indicator that it's combustion reaction. It's going to require a bit of energy for this reaction to take place but it's going to release a lot more energy than it needs. Indicating this is exothermic reaction, our products will always without a doubt, always, always be a carbon dioxide and water. If the reaction is a complete reaction, meaning we put in enough energy for this reaction to take place fully. If we didn't put in enough energy the reaction will still take place but it won't be as quite as strong so it'll give us the products of carbon monoxide not very good, very poisonous actually and water. That's an indicator that it's an incomplete combustion reaction. Alright so combustion reactions are always fun to watch. So let's actually look over here and watch a video on combustion reaction in action.

Alright so what exactly happened in that video? Okay so we had, the guy had ethanol in an aqueous solution and he put it inside that big container okay ethanol's compound looks like this C2H5OH reacts with oxygen which is the source of the flame, so you put a flame in there and that's our source of oxygen gas and it reacted okay and it gave us carbon dioxide as a gas so all the oxygen was eaten up and gone away and now we have carbon dioxide left and we have water as you saw him pouring out the water in liquid form out of the container. So why did it crush? Well we look at it and say okay we've for everey, in the product reacts side here we have 3 particles of oxygen gas for every 2 particles of carbon dioxide gas. so we're actually losing from gas in this reaction all these guys are getting up, these are going to go away and only 2 gas particles are going to be produced in its place. So that means we have less we've got [IB] particles and so the volume is actually much smaller which is the reason why it crushed down.

And then at the end, we also saw him pour out the water to prove that there was water by-product. Alright so that is combustion reactions.