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Synthesis 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 synthesis reaction is a type of reaction in which multiple reactants combine to form a single product. Synthesis reactions release energy in the form of heat and light, so they are exothermic. An example of a synthesis reaction is the formation of water from hydrogen and oxygen. Synthesis is, in essence, the reversal of a decomposition reaction.

Alright there're millions and millions of different types of chemical reactions that take place in nature one of them that you might see in class would be the synthesis reaction also known as the combination reaction. This is when a chemical or 2 or more substances react to form a single product. That's your clue that it's a synthesis reaction or a combination reaction the single product. Okay it's when one substance combines with another substance to form again a single product. That's your hint, okay so what kinds of things will undergo this? Well we have 2 elements that come together, we have a sodium metal can combine with chlorine gas to form our table salt sodium chloride, notice we have just because there're 2 of them doesn't mean that this is not a single product.

If you just have one product over here, no plus sign that means it's a synthesis reaction. Another type is in carbon reacts with oxygen gas carbon dioxide or carbon monoxide. Now notice that this one is only one possible product that can take place because it's ionic. We know that ionic compounds normally have one type of compound together or one possible combination. However these 2 are non-metal or are gases, we can have several different types of products. We can have either carbon dioxide or carbon monoxide depending on what actually is happening here or possibly both in separate different reactions. Or 2 compounds can come together we have calcium oxide can combine with water to produce calcium hydroxide. Notice again a single product, or a compound and an element can come together sulfur dioxide plus oxygen gas yields 2 sulfur trioxide gas particles.

I do also want note that because these 2 react with oxygen, this also can be classified as combustion reactions which you can learn about in another video in more detail. Alright so let's actually look at a video describing what a synthesis reaction looks like. So we have combined sulfur particles and iron particles, sulfur is the yellow and iron is the black in order to combine them and mix them together to form a mixture and so we can have them all mixed throughout in this beaker. And then what we're going to do is we are going to put it on the table and so we're going to spread it out, so we have more surface area so because the greater the surface area you have the better reaction is going to take place. So we're going to pour it all on the table and then we're actually going to require a little bit of energy okay so an energy in this case is going to be in the form of heat. So we're going to bring over a Bunsen Burner which you probably have seen in class and we're going to light it and we're going to actually use the glass rod through the Bunsen Burner and we're actually going to heat up the glass rod, so we can actually have some energy, some thermal energy in this glass rod.

Okay and this is actually for some reason take a really long time on this video, so I'm just going heat it up because glass does take quite a awhile to heat up and actually retain that heat and then we're going to touch it to the mixture that we have of sulfur and iron. And notice this huge amount of energy that was released okay. That is showing us that synthesis reactions are exothermic meaning it releases energy. It might require a bit of energy but it releases a lot more than it requires. And now we have a new substance, this is iron sulfide. Okay that's our new substance and it has different properties, it completely reacts differently, notice it's all big block of new compound that's an example of synthesis reaction one of the reactions that you'll see in class.