Molecules are like the building blocks of different materials because they help make up various substances. Let's take a closer look at why they are important:

What is a Molecule?

• A molecule is a group of two or more atoms that are connected together.
• Sometimes the atoms can be the same, like in O₂ (oxygen).
• Other times, they can be different, like in H₂O (water).

What is a Compound?

• A compound is a special kind of molecule that has at least two different types of elements in it.
• For example, NaCl (table salt) and CO₂ (carbon dioxide) are compounds because they have different kinds of atoms combined together.

Why Molecules Matter

1. Composition: Molecules help decide what a compound is made of.

   • For instance, in H₂O, there are two hydrogen atoms and one oxygen atom.
   • This mix gives water its special properties, which are very different from the properties of just hydrogen or oxygen.

2. Chemical Properties: How the atoms are arranged in a molecule changes the properties of the compound.

   • For example, water boils at 100°C, but hydrogen gas boils at −253°C.

3. Molecular Ratio: In compounds like CO₂, the ratio of carbon to oxygen is 1:2.

   • This ratio helps us understand how different compounds are formed and how they react with each other.

Some Cool Facts

• About 90% of all known substances are organic compounds, which include molecules that contain carbon.
• There are more than 10 million different compounds recorded, showing how many different ways atoms can join together.

In summary, molecules are the basic units that form compounds. They have special properties based on how the atoms are arranged and connected.