An easy way to think of a chemical reaction is to think of the process of making a cake. We mix all the ingredients together (flour, butter, salt, sugar and eggs), and after baking, this mixture turns into food (cake). In chemical terms, the equation is the recipe, the ingredients are the "reactants," and the cake is the "product." All chemical equations look like "A + B C (+ D..)", where each letter represents an element or molecule (a group of atoms held together by chemical bonds). The arrow symbolizes the reaction or change that occurs.
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Part 1 of 3: Learning the Basics of Chemistry
Step 1. Study the periodic table
Atoms are the basic units that make up a chemical substance. Atoms (elements) can be found in the periodic table. The periodic table of the elements is found in most chemistry textbooks or online and provides a wealth of information. This table tells us the atomic number (number of protons in an atom's nucleus), atomic mass (number of protons and neutrons in an atom's nucleus), as well as the atomic symbol for an element.
The symbol for an element can be a single capital letter or a capital letter followed by a lowercase letter. For example, C is for carbon and He is for helium
Step 2. Remember how an element forms in nature
Pure carbon can be found as graphite or diamond, and is denoted by the letter C.
Many elements that are gases at room temperature must bond with each other to be stable. These pairs of atoms are called diatomic molecules. For example, 1 oxygen atom is unstable. The air we breathe contains the diatomic pair O2 (which is stable), as does N2, which is a stable form of Nitrogen
Step 3. Know how to write a molecular formula correctly
A molecular formula is a sequential arrangement of the atoms in the molecule, with each atomic symbol followed by a subscript number indicating the number of atoms of a particular type in an element.
For example, the methane molecule is made up of 1 carbon atom and 4 hydrogen atoms, so it is written as CH4. Other household chemicals such as ammonia gas (NH3) or clothes bleach (HClO4) are written this way
Part 2 of 3: Writing Chemical Equations
Step 1. Know the reactants in the equation
The reactants are to the left of the arrow. Reactants represent the starting materials for the chemical reaction we are writing about. Reactants are expressed as atoms or molecules or a combination of both.
For the chemical reaction: Fe + O2 Fe2O3, the reactants are: Iron (Fe) and Oxygen (O2)
Step 2. Know the product in the equation
The product is to the right of the arrow. The product indicates the molecule that results from the chemical reaction we are writing about. Products can also be written as atoms or molecules or a combination of the two.
For the chemical reaction: Fe + O2 Fe2O3, the products are: Iron (III) Oxide (Fe2O3), or rust
Step 3. Remember that this equation is not yet balanced
The reaction of iron turning into rust (iron oxide) requires iron and oxygen, so the reactants are Fe and O2 and the product is Fe2O3. Then the equation that represents this reaction is Fe + O2 Fe2O3. However, this is not accurate because it is not yet balanced.
Part 3 of 3: Balancing Chemical Equations
Step 1. Remember Dalton's atomic theory
Atoms can neither be created nor destroyed during a reaction (except for nuclear reactions, which is beyond the scope of this article). This means that all atoms on either side of the arrow must be counted.
For example, the Fe + O2 Fe2O3 equation for rusted iron as written is incorrect. 1 Fe and 2 O react, but the result is 2 Fe and 3 O. To justify it, adjust the amount and ratio of the inputs. With some experiments, it can be seen that 4 Fe + 3 O2 2 Fe2O3. Four iron atoms are on either side of the arrow and six oxygen atoms are also on either side of the arrow. All numbers must be used in the equation because there is no such thing as a half molecule, so writing the equation 2 Fe + 11/2 O2 Fe2O3 is incorrect
Step 2. Write the correct final chemical equation
For the example reaction we have worked on (iron and oxygen react to form rust), the final correct equation is:
2 Fe + 3O2 2 Fe2O3
Step 3. Practice
Try the reaction of burning methane and oxygen to produce carbon dioxide and water: CH4 + O2 CO2 + H2O. What are the coefficients of each molecule? The result is CH4 + 2O2 CO2 + 2H2O. On each side of the arrow is 1 carbon, 4 hydrogen, and 4 oxygen. Many websites provide problem sets or additional help with balancing equations.
