Moles and masses
Lesson details
Learning outcome
I can calculate mass of a substance or the number of moles it contains from data.
Key learning points
- The number of particles (atoms, ions, molecules etc.) in one mole of a substance is always the same.
- The mass of one mole of a substance is equal to the relative mass of the substance measured in grams.
- Mathematical relationships are manipulated to process practical results, calculating the number of moles in a substance.
Keywords
Mole - 1 mole of a substance is 6.02 × 10²³ particles of it. The mass of a mole of a substance is its relative mass in grams.
Avogadro's constant - Avogadro's constant is the number of particles in one mole of a substance (6.02 × 10²³ mol⁻¹).
Relative formula mass - The relative formula mass (RFM or Mᵣ) of a substance is the sum of the relative atomic masses of all the atoms in its formula.
Common misconception
Pupils struggle to link a mole to number of particles.
Use real world examples of converting volumes / masses into number of particles so pupils become more comfortable converting between moles, number of particles particles and masses.
Teacher tip
Alter the final task into a competition - who can fit the highest number of water molecules onto a penny? Challenge pupils to peer evaluate each other's working out to ensure the winners have correctly calculated the number of molecules. Consider extending to include different coins.
Equipment
balances, pennies, small beakers, water, dropping pipettes, paper towels, calculators
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which of the following is the correct chemical formula for calcium carbonate?
Q2.Match each keyword to the correct definition.
describes a reaction, indicating the reactants and products
shows the number of atoms of each element in a substance
number placed in front of a chemical formula to balance an equation
written slightly below and to the side of another character
indicates the physical state of substances in a reaction
Q3.Which chemical equation is correctly balanced?
Q4.Match each element to its correct relative atomic mass.
4
9
19
20
11
23
Q5.The relative formula mass of sodium sulfide, Na₂S is .
Q6.The relative formula mass of Al(OH)₃ is .
Assessment exit quiz
6 Questions
Q1.Which equation best matches this description of a chemical reaction? "Four moles of aluminium atoms react with three moles of oxygen molecules to form two moles of aluminium oxide formula units".
Q2.Which of the following shows a correct mathematical relationship between moles, mass (g), and a substance's relative formula mass (RFM)?
Q3.The standard unit for mass in chemistry is .
Q4.Sort the following substances into order of increasing mass.
Q5.How does the number of particles in 10 g of nitric acid, HNO₃, compare to the number of particles in 10 g of nitrogen?
Q6.Match the mass (g) of the following substances to the correct number of moles.
0.5 mol
1.0 mol
1.25 mol
1.5 mol
1.75 mol
2.5 mol
To help you plan your 10 chemistry lesson on: Moles and masses, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 chemistry lesson on: Moles and masses, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 chemistry lessons from the Calculations involving masses unit, dive into the full secondary chemistry curriculum, or learn more about lesson planning.