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Chemical reactants and products

Pearson
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In this lesson, we will distinguish between chemical reactants and products that make up a chemical reaction. But first, let's think about something we all learned when we were young. Colors! When we combine blue and red, for example, we don't end up with blue and red. We get something new. Right? We get purple. Similarly, when a chemical reaction occurs, we typically start with one or more molecules or compounds and end up with something different. Let's look at this concept using letters to represent the different chemicals that are involved in the chemical reaction. In this example, chemical compound A and chemical compound B, when put together, give us chemical compound C. Another way to think of this is to say that compounds A and B react together to produce compound C. And this is where the terms reactant and product come from. Reactants react to produce products. Simple, right? Notice that in a chemical reaction an arrow is used to indicate the direction in which the reaction proceeds. The arrow separates the reactants from the products. Reactants appear before the arrow and you can think of the arrow as meaning "produces". The products appear after the arrow. Of course, real chemical reactions are often more complicated than just A plus B produces C. Let's look at one example. Here we are looking at three sugars. Glucose and fructose react to form sucrose, which is table sugar. In this case, glucose and fructose are the reactants and sucrose is the product. But look carefully at the arrow. You should notice that there are two arrows running parallel to each other, one going forward and one going backward. This indicates that this is a reversible reaction, which means that it may occur forward or backward depending on the conditions at the time. If the reaction occurs as written, glucose and fructose are the reactants and they produce sucrose. However, if glucose or fructose is needed instead, the sucrose can be broken down. This reaction is the opposite of the first one and is indicated here by the backwards arrow. Now the reaction begins with sucrose, so sucrose is now the reactant and glucose and fructose are produced when sucrose is broken down so they are the products. Instead of writing both reactions separately, it is simpler to write them together and to merely add the double arrow in the middle to indicate that the reaction may occur in either direction. When you see this, just remember that the reactants react to produce products, so if you read the reaction in the direction that it occurs then you will always know which chemicals are reactants and which are products. Just follow the arrow.
In this lesson, we will distinguish between chemical reactants and products that make up a chemical reaction. But first, let's think about something we all learned when we were young. Colors! When we combine blue and red, for example, we don't end up with blue and red. We get something new. Right? We get purple. Similarly, when a chemical reaction occurs, we typically start with one or more molecules or compounds and end up with something different. Let's look at this concept using letters to represent the different chemicals that are involved in the chemical reaction. In this example, chemical compound A and chemical compound B, when put together, give us chemical compound C. Another way to think of this is to say that compounds A and B react together to produce compound C. And this is where the terms reactant and product come from. Reactants react to produce products. Simple, right? Notice that in a chemical reaction an arrow is used to indicate the direction in which the reaction proceeds. The arrow separates the reactants from the products. Reactants appear before the arrow and you can think of the arrow as meaning "produces". The products appear after the arrow. Of course, real chemical reactions are often more complicated than just A plus B produces C. Let's look at one example. Here we are looking at three sugars. Glucose and fructose react to form sucrose, which is table sugar. In this case, glucose and fructose are the reactants and sucrose is the product. But look carefully at the arrow. You should notice that there are two arrows running parallel to each other, one going forward and one going backward. This indicates that this is a reversible reaction, which means that it may occur forward or backward depending on the conditions at the time. If the reaction occurs as written, glucose and fructose are the reactants and they produce sucrose. However, if glucose or fructose is needed instead, the sucrose can be broken down. This reaction is the opposite of the first one and is indicated here by the backwards arrow. Now the reaction begins with sucrose, so sucrose is now the reactant and glucose and fructose are produced when sucrose is broken down so they are the products. Instead of writing both reactions separately, it is simpler to write them together and to merely add the double arrow in the middle to indicate that the reaction may occur in either direction. When you see this, just remember that the reactants react to produce products, so if you read the reaction in the direction that it occurs then you will always know which chemicals are reactants and which are products. Just follow the arrow.