Balancing Chemical Equations

A reactant

is a chemical substance that is present at the start of the reaction. There can be one or more reactants involved in a chemical reaction.

A product

is a new substance that is formed during a chemical reaction.

A chemical reaction

is a process that involves the rearrangement of the atoms in reactant molecule(s) to form new molecules

evidence of a chemical reactions

When a chemical reaction occurs you will observe one or more of the following: energy is produced or used

A chemical formula

is a symbolic representation that uses element symbols and numbers as subscripts to show the composition of a chemical substance.

A chemical equation

is a symbolic representation of what occurs when reactants are converted to products during a chemical reaction.

Subscripts

are used to show the number of each type of atoms in a chemical substance. They are written as a small number after the element symbol.

A coefficient

is a number written before a chemical formula to show how many molecules (or moles) are present.

State of matter

After each formula there is a symbol that indicates the state of the substance: solid (s)

Aqueous solution (aq)

a solute dissolved in a solvent

Solute

the solid that goes into a solution (i.e. the NaCl in salt water)

Solvent

the liquid that does the dissolving in a solution (I.e. the water in salt water)

The Law of Conservation of Mass

states that the mass of the reactants must equal the mass of the products.

Balanced equation

you must use coefficients in a chemical formula to obey the law of conservation of mass

What is the product in this reaction?

2 water and carbon dioxide

What is the reactant in this reaction?

Carbon tetrahydride and 2 oxygen molecules.

Why does this equation use Coefficients?

To balance the number of atoms on both sides of the equation, ensuring mass is conserved during the reaction.

Why does this reaction use subscripts?

To show the ratio of atoms within a compound.