**Why is the mole concept so confusing?**

The mole concept has been recognized as one of the most difficult topics to teach and learn. This is due to its abstract, theoretical nature.

**How do you measure atoms and molecules?**

In baking, you can easily measure the amount of ingredients by using cups or weighing scales. In chemical reactions, however, it's physically impossible to count the number of atoms or molecules there are in a given amount of substance. That's why scientists have devised a clever way to overcome this problem.

**Using moles for counting atoms and molecules**

Do you know that in DIY stores, nails are usually purchased using mass rather than by counting individual nails? It's not practical to count small items as it is too time consuming. You can easily convert from mass to number by using a conversion factor called unit mass. For example, if you know the mass of ten nails, you can easily work out the mass of fifty nails. And nails are often sold in units of ten, twenty, thirty, etc. The same principle applies to chemistry and chemists work out the number of atoms by weighing.

The periodic table holds the unit mass for known elements. If you know the mass of a substance, you can refer to the periodic table and calculate the number of moles. And if you know the number of moles, you can easily calculate the number of atoms or molecules.

**Avogadro's Constant, N**_{A}

_{A}

A **mole is a unit** that represents a very large and unique number. The number it represents is **6.022x10^23**. This number isn't randomly chosen but it's related to **Avogadro's number** which is based on the hypothesis that all gases at the same temperature and pressure occupy equal volumes of space and they have the same number of particles.