Chemical Equations and Reactions

Study Notes

A chemical equation is a chemical reaction written in the form of an equation.
There are two types of chemical equations: word equations and formula equations.

A word equation is a chemical reaction written in terms of the full names of the reactants and products.
The reactants are written first, followed by an arrow (→), which means "forms" or "gives", and then the products.
If there are multiple reactants or products, they are joined by the '+' sign.
The '+' sign has different meanings on each side of the equation: on the reactant side, it means "reacts with", and on the product side, it means "and" or "in addition to".
The conditions required for the chemical change can be written above the arrow to make the equation more informative.
The state of reactants and products can be expressed using the following signs: 's' for solid, 'l' for liquid, 'g' for gas, and 'aq' for a solution in water.

A formula equation is a scientific way to express a chemical reaction using symbols and molecular formulas of reactants and products.
Formula equations can be balanced or unbalanced.
Formula equations use molecular formulas of reactants and products instead of their full names.

Chemical changes occur when zinc reacts with sulfuric acid to produce zinc sulfate and hydrogen gas, and zinc displaces the hydrogen atom of sulfuric acid.
Calcium carbonate decomposes to calcium oxide and carbon dioxide when heated, undergoing dissociation.
Magnesium combines with oxygen to produce magnesium oxide when burnt.

A chemical reaction brings about a chemical change, such as when nitrogen reacts with hydrogen to form ammonia.
A chemical reaction consists of reactants and products, separated by an arrow (→).
Reactants are substances that undergo a chemical change during a chemical reaction, such as nitrogen and hydrogen in the ammonia formation reaction.
Products are substances formed as a result of a chemical change in a reaction, such as ammonia in the same reaction.

A chemical equation represents a chemical reaction, with reactants on the left and products on the right, separated by an arrow (→).
An example of a chemical reaction is the reaction between dilute hydrochloric acid and calcium carbonate (marble), producing calcium chloride, water, and carbon dioxide, accompanied by fizzing air bubbles.