Just like mathematical equations, chemical equations allow us to convey a large amount of information in a very brief and clear way. In this video, we're going to learn how to interpret these equations. So to begin, let's look at the parts of a chemical equation.

When a chemical reaction occurs, you begin with the reactants. These are the substances that are going to react together. The arrow after the reactants represents the chemical reaction itself, and can be read as “yields” or “produces.” Then, to the right of the arrow, you have the products, which are the substances that are produced in the chemical reaction. Sometimes, you'll see a substance written above the arrow. This is called a catalyst, and it's a substance that is not actually consumed or produced in the chemical reaction, it just allows the reaction to proceed more quickly.

Along with the chemical formulae for the substances involved, we can also use chemical equations to indicate the state of matter for each of the substances. We do this by using abbreviations for each phase in parentheses after the chemical formula. To indicate a solid phase, we use an “s” in parentheses. The example shown is for solid sodium chloride. Liquids are indicated with an “L.” This is how you indicate liquid hydrogen peroxide. Gasses are indicated with a “g,” like shown here with nitrous oxide, sometimes called dinitrogen oxide. And lastly, aqueous solutions, which are formed when a substance - be it solid, liquid, or gas - is dissolved in water, those are indicated with the letters “aq”. For example, an aqueous solution of hydrogen chloride is how we form hydrochloric acid.

With this information, let's look at putting together a chemical equation. Let's write the chemical equation for the following reaction: An aqueous solution of sodium chloride reacts with an aqueous solution of silver nitrate to produce an aqueous solution of sodium nitrate and solid silver chloride.

Well, an aqueous solution of sodium chloride is NaCl(aq), and an aqueous solution of silver nitrate is AgNO3(aq). We separate substances with a plus sign, so the reactant side of our chemical equation will look like this.

Those two react to produce - so we draw an arrow - an aqueous solution of sodium nitrate, that is NaNO3 aq, and - so we draw a plus sign - solid silver chloride, which is AgCl(s). And this is the chemical equation for this reaction.

Looking at this chemical reaction, it must obey what is called the law of conservation of mass. That means that mass, and thus matter, are never created or destroyed in a chemical reaction. To better understand this, let's look at the chemical equation we just created. The two critical consequence of the law of conservation of mass are: first, that the mass of the reactants must equal the mass of the products. The other important result of this law is that the quantities of each element must also be preserved. For example, if there are three oxygens in the reactants, there must also be three oxygens in the products.

In the next video, we'll look more at how we apply the law of conservation of mass when we are creating chemical equations.