ChemThink: Chemical Reactions

The materials left at the end of a reaction are called products.

Let's take a look at these reactions. What do all three of the products have in common?
Their bonds are being rearranged. Rearranging bonds is necessary for a chemical reaction.

Generally, we don't draw pictures when showing reactions. We use chemical symbols.

The first reaction is the bonding of Fe and S-- Fe + S-- which results in FeS.
The second reaction is the splitting of CaCO3, which results in CaO + CO2.
The third reaction is the splitting of H2 and Cl2 along with the joining of Mg and Cl. This goes from 2 HCl + Mg to H2 + MgCl2.

In every chemical reaction, the chemicals at the end are the exact same ones as the ones at the beginning. No chemicals are ever removed or added in a chemical reaction, since chemical reactions are just rearrangements of the bonds between atoms.

This is not the correct way to make water, since there is an extra oxygen molecule. To fix this, we must add two more hydrogen molecules.

Now, that's water!

Each atom on the reactant side must also be on the product side. This idea is the Law of Conservation of Mass. There must be all of the same atoms before and after every reaction.

This is not a balanced equation because there are two oxygen atoms on one side but only one on the other. To represent the chemical reaction, we need to add another CuO.

Uh oh! Now the Cu atoms are unbalanced! We have to use two Cu atoms to interact with each O2 molecule, so if we use these two reactants it will produce two molecules of CuO.

Now it's balanced!

Let's try balancing this one using only these molecules.

There! Let's try a more difficult one.

Solved. Now let's try one without the scale.

And another...

Good! These are the sheer basics of chemical reactions, but it's easy to make more complex reactions if you know the basics!