Chemical Reactions and Equations
1. Chemical Reactions
A chemical reaction involves a chemical change where one or more substances
(reactants) are converted into new substances (products).
Indicators of a chemical reaction:
o Change in state
o Change in color
o Evolution of gas
o Change in temperature (heat/light produced or absorbed)
o Formation of a precipitate
2. Chemical Equations
Representation of a chemical reaction using symbols and formulas.
Example:
Mg+O2→MgO
Reactants: Substances before reaction (left side).
Products: New substances formed (right side).
➤ Word Equation
Reactants and products written in words.
Example:
Magnesium + Oxygen → Magnesium oxide
➤ Balanced Chemical Equation
Has equal number of atoms of each element on both sides (Law of Conservation of
Mass).
Example:
2Mg+O2→2MgO
➤ Unbalanced Equation (Skeleton Equation)
Atom counts are not equal on both sides.
➤ Steps for Balancing:
1. Write the skeleton equation.
1. Chemical Reactions
A chemical reaction involves a chemical change where one or more substances
(reactants) are converted into new substances (products).
Indicators of a chemical reaction:
o Change in state
o Change in color
o Evolution of gas
o Change in temperature (heat/light produced or absorbed)
o Formation of a precipitate
2. Chemical Equations
Representation of a chemical reaction using symbols and formulas.
Example:
Mg+O2→MgO
Reactants: Substances before reaction (left side).
Products: New substances formed (right side).
➤ Word Equation
Reactants and products written in words.
Example:
Magnesium + Oxygen → Magnesium oxide
➤ Balanced Chemical Equation
Has equal number of atoms of each element on both sides (Law of Conservation of
Mass).
Example:
2Mg+O2→2MgO
➤ Unbalanced Equation (Skeleton Equation)
Atom counts are not equal on both sides.
➤ Steps for Balancing:
1. Write the skeleton equation.
