A Level Chemistry OCR Practice Exam

What unit is used to measure 'amount of substance' in chemistry?

1. Liter

2. Mole

3. Gram

4. Newton

The correct answer is: Mole

In chemistry, the term "amount of substance" is specifically quantified using the mole. This unit is a fundamental concept that allows chemists to count particles by weighing substances. One mole of any substance contains Avogadro's number of entities, which is approximately \(6.022 \times 10^{23}\) particles, whether they are atoms, molecules, ions, or other entities. The mole provides a bridge between the macroscopic scale of substances we can measure in the lab and the microscopic scale of atoms and molecules. This capability is crucial for stoichiometric calculations in chemical equations, enabling chemists to determine the proportions of reactants and products involved in chemical reactions. Other units, such as liters, grams, and newtons, serve different purposes in different contexts: liters measure volume, grams measure mass, and newtons measure force. While these units may be involved in various calculations in chemistry, they do not specifically quantify the amount of substance. Therefore, the mole remains the designated unit for this measurement, highlighting its importance in chemical science.