Chemical reactions and Equations

Chemical Reactions and equations

Quick chapter summary


What Is a Chemical Reaction?

A chemical reaction is a process in which one or more substances
(reactants) change into new substances (products) with different
properties.
General Form

Reactants → Products
Example:

2H2+O2→2H2O2H_2 + O_2 \rightarrow 2H_2O2H2
+O2→2H2O


Indicators of a Chemical Reaction

A chemical reaction may involve:
●Change in colour
●Change in temperature (heat released or absorbed)
●Formation of gas
●Formation of a precipitate (solid)
●Change in smell

, Writing Chemical Equations
Word Equation

Magnesium + Oxygen → Magnesium oxide
Balanced Chemical Equation

2Mg+O2→2MgO2Mg + O_2 \rightarrow 2MgO2Mg+O2
→2MgO


Why Are Equations Balanced?

According to the Law of Conservation of Mass , atoms are neither
created nor destroyed. Therefore, the number of atoms of each element
must be the same on both sides.


Types of Chemical Reactions
1. Combination Reaction

Two or more substances combine to form one product.

2H2+O2→2H2O2H_2 + O_2 \rightarrow 2H_2O2H2
+O2→2H2O
2. Decomposition Reaction

One compound breaks into simpler substances.