Chemical Reactions: A basic tutorial

On Saturday I was making cinnamon rolls for my family. And it occurred to me how many chemical reactions take place in everyday processes. When I make a batch of cinnamon rolls, a lot of chemical reactions are taking place. Just the conversion of sugar to carbon dioxide and water involves a major metabolic pathway.

This week's video covers the basics of chemical reactions. If this is an area where you need help in chemistry, you should also see last week's video on chemical bonds, here:

If you're already familiar with chemical reactions, you should watch the following videos on orbitals, photosynthesis and respiration. Here are the links:


And finally, here is this week's video:

The sugar, along with oxygen in the air are the reactants. In other words, they are the chemicals that are going to react in the chemical reaction. Easy peasy, right?

What is a chemical reaction?

You could define a chemical reaction as the breaking and forming of covalent bonds. The carbon in the sugar breaks away and forms a chemical bond with the oxygen, creating carbon dioxide. The leftover oxygen and hydrogen form a covalent bond, creating water.

Chemical reactions can be reversed, but this isn't as straightforward as you might think. If it were, then perhaps the water and carbon dioxide would recombine in a reverse chemical reaction, creating sugar. Obviously this doens't happen very much, or you would be coughing up lollipops every time you exhaled in the rain.

Chemical reactions are helped or hindered by energy, temperature, enzymes, and the relative abundance of reactants. If you have dry sugar just sitting on a table at room temperature, it won't turn into carbon dioxide. But if an organism consumes the sugar, then you'll see it transformed.

Likewise, to turn water and carbon dioxide into sugar, you need a lot of energy inputs. Plants make this transformation, using energy from the sun in the process known as photosynthesis. Without this energy input, your carbon dioxide will not turn back into sugar.

However, many chemical reactions are reversible under common conditions. And this suggests that the products of a reactiom must be made of the same "stuff" as the reactants. This is known as conservation of matter. If you count the carbon atoms in a molecule of glucose (sugar), and then count the carbon atoms in the carbon dioxide after the chemical reaction takes place, you'll find the same number of atoms.

This chemical reaction accounting is known as stoichiometry, or the measure of atoms of an element before and after a chemical reaction.

By the way, a man named Jon told me how to make yeast-risen cinnamon rolls more than 20 years ago. The yeast gives the rolls a sourdough flavor that goes well with green tea, I think.

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