We see and experience chemical reactions everyday, whether it is from the rust on your mailbox, cellular respiration, or having to start your car.
A chemical reaction is the process of one or more atoms that are split apart and then recombined to create a new substance. When a chemical reaction occurs chemical bonds of an atom break apart and then recollect. One of the most popular examples of a chemical reaction is rust. When iron (Fe) combines with oxygen (O2) it creates a chemical compound called iron oxide (Fe2O3) or so called rust. In general this means for every 2 iron atoms there are 3 oxygen atoms that all combine together to make Iron Oxide.
All chemical equations have reactants and products. The reactants are the starting substances and the product is the resulting chemical compound that is formed from the reactants combining. Lets go back to rust (Fe2O3). We would use the distributive property to break this compound apart. Fe x2 + O x3. These are the reactants in this chemical equation. The product, which would be all of the atoms in the reactant combined would be Fe2O3 (rust).
The conservation of mass states that matter can not be created nor destroyed. This means that when a chemical reaction occurs, the product has the same amount of matter than the reactants. The atoms transform recombine to transform themselves into a different substance but those same atoms that were once split apart are still there, in the new substance. Lets take the chemical equation of photosynthesis for an example. C6H12O6+6O2 are the reactants and 6CO2+6H2O is the product. Lets dissect the reactants. There are 6 carbon atoms, 12 hydrogen atoms, and 18 oxygen atoms. Now, lets take a good look at the product. There are as well, 6 carbon atoms, 12 hydrogen atoms, and 18 oxygen atoms. This supports that matter can not be created nor destroyed. All of the same atoms are still there, but in a different form.
An interesting way to think of chemical reactions is when you make a cookie. The two main ingredients are flour and sugar and there are several other ingredients that are added to complete the recipe of a cookie. Think about it for a moment. The reactants are the flour, sugar, and other ingredients, and when energy is applied to these ingredients (in this case heat) the product is a cookie. This reenacts the concept of atoms and the chemical compounds that they form.
Chemical reactions are a essential part of the planet earth. They allow living things to grow, develop, reproduce, and adapt. In general they keep our world running, and will continue to do so forever.