###### Worksheets and lesson ideas to challenge students aged 11 to 16 to think hard about mole calculations (GCSE and Key Stage 3)

*The mole can be a tricky concept for students to master. It is therefore important to introduce the concept in a clear way when teaching it for the first time.*

*A mole is just a number. Just as a dozen equals 12 and a pair equals 2, a mole equals 6.02 X 10*

^{23}. You can have a mole of biscuits, just as you can have a dozen biscuits.*Showing students early on that a mole of any substance will have a different mass helps them understand the equation a=m/Mr. The teaching resources below support all areas of quantitative chemistry.*

*This fantastic video introduces the concept of a relative scale and looks at how chemists are redefining the mole*.

#### Introducing relative formula mass

The diffusion in liquid demo,involving lead nitrate and potassium iodide, is a great starting point to get students to understand that different atoms/ions have different masses and hence move at different rates in solution. From here you can explore relative formula, and possibly investigate the diffusion of other substances that have different relative formula masses.

#### Empirical formula

I always used to struggle to think of a good way to introduce empirical formula to students – why do we care?! I then saw a lesson where students were asked to count sodium and chloride ions in a giant lattice structure and oxygen and silicon atoms in sand – the need for an empirical formula then became clear! This serves as a simple but powerful starting point that provides a rationale for why we care about empirical formulas.

#### What is a mole?

GCSE notes on understanding the mole. This simple introduction to the mole asks students to calculate molar masses for different substances. It provides a starting point to introduce the concept of Avogadro’s number. The mole is introduced simply as a number – albeit a large one. It also looks at why chemists need such a concept in the first place. (PDF)

#### Calculating percentage yield

GCSE practical on percentage yield and reacting masses making MgO. This classic practical asks students to prepare MgO, calculate the percentage yield and evaluate the method. It puts percentage yield calculations in context as students imagine they are making a heartburn remedy for a pharmaceutical company. Contextualising the problem helps students see the relevance of this calculation. (PDF)