Lesson 8: The Use of Chemical Formulas to Represent Chemical Reactions (Balancing of Equations)

Chemicals react to change

The “chemicals” in a chemical reaction are elements or compounds. They “react” when combined or broken down.

Element

is a pure substance and cannot be broken down into a new one

Compound

is a combination of pure substances

Substance

a pure form of matter with a specific and uniform composition, meaning it's made up of only one type of atom or molecule. Substances can be elements (like gold or oxygen) or compounds (like water or salt). They have distinct properties and cannot be separated into simpler components by physical means. 

Chemical Change

A process where one or more substances are transformed into new substances with different chemical properties. Occurs through chemical reactions, resulting in the breaking and/or formation of chemical bonds. The change is often irreversible.

Examples of Chemical Change

Using chemical batteries, the explosion of fireworks, rotting bananas, rusting of iron

Reactants(ingredients)

starting substances

Products

new substances formed

Chemical equations provide?

a concise and universal way to describe chemical changes.

Chemical equation

tells the story of a chemical reaction

Chemical reaction

is essential when planning an experiment, the reactants are always written before the reaction or on the left side of the equation while the product is on the right side of the equation.

“Ingredients → Final Dish”

Reactants → Products H2 + O2 → H2O

Why do the chemical equation needs to be balanced?

so that it follows the law of conservation of mass.

Who discovered the law of conservation mass?

Antoine Lavoisier, a French chemist, who formulated it in 1789

Law of Conservation of Mass

Matter (atoms) cannot be created or destroyed in a chemical reaction.