Converting between mass and volume using moles
Lesson details
Learning outcome
I can combine mathematical relationships to calculate an unknown mass or volume.
Key learning points
- The volume of one mole of any gas at room temperature and pressure (20℃ and 1 atmosphere pressure) is 24 dm³.
- Reacting mass calculations can use a combination of mass to volume calculations and vice versa.
- Amount of substance (moles) can be calculated using multiple equations.
- The choice of equation for calculating moles depends on the context of the problem or calculation.
Keywords
Mole - A mole of something is 6.02 × 10²³ of it. The mass of a mole of a substance is its relative mass expressed in grams.
Volume - Volume is how much 3D space matter occupies. It is usually measured in cm³.
Molar gas volume - Molar gas volume is the volume occupied by one mole of any gas. It is equal to 24 dm³ or 24 000 cm³ at room temperature and pressure.
Stoichiometry - Stoichiometry refers to the molar ratio of the reactants and products in a chemical reaction.
Balanced symbol equation - A balanced symbol equation describes a reaction using a symbol equation with coefficients, which ensure there are equal numbers of atoms of each element on both sides of the symbol equation.
Common misconception
Pupils use an incorrect mathematical relationship to calculate the number of moles in a sample.
Depending on the type of substance (solid, solution or gas) a specific mathematical relationship for moles must be used. Challenge pupils to classify substances as (s), (aq), or (g) and apply correct mathematical relationship.
Teacher tip
Limestone is roasted with clay to form cement, producing carbon dioxide in the process. Challenge pupils to determine the volume of carbon dioxide produced when a sample of limestone decomposes when heated.
Equipment
Sample of limestone (calcium carbonate), balance, tongs, heatproof mat, Bunsen burner, tripod, gauze.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which unit is most commonly used to measure the volume of a gas?
Q2.What is the molar gas volume of any gas at room temperature and pressure (20°C and 1 atmosphere)?
Q3.Molar gas volume is the volume occupied by of any gas at room temperature and pressure, standardised at 24 dm³ or 24 000 cm³.
Q4.Which equation would you use to calculate the number of moles from the volume of a gas?
Q5.True or false? The number of moles of a gas can only be calculated if you know the volume of the gas and the conditions of temperature and pressure.
Q6.Calculate the volume of 0.5 moles of nitrogen gas at room temperature and pressure. Assume the molar gas volume is 24 dm³ per mole. Give your answer to 2 s.f.
Volume of nitrogen gas = dm³.
Assessment exit quiz
6 Questions
Q1.When converting the volume of a gas to the mass of a solid reactant in a balanced reaction, what must you first determine?
Q2.Order the following steps to calculate the mass of a solid reactant from the volume of a gas product in a chemical reaction. Starting with the volume of gas.
Q3.If 24 dm³ of hydrogen gas react with oxygen to form water, how many moles of oxygen gas were used?
2H₂ + O₂ → 2H₂O.
Q4.A sample of oxygen gas weighing 16 grams is used in a reaction. Calculate the volume it occupies at room temperature and pressure.
The RFM of oxygen (O₂) is 32.
The molar gas volume is 24 dm³
Q5.Calculate the volume of CO₂ gas produced when 100 g of CaCO₃ decomposes.
CaCO₃ → CaO + CO₂.
Assume all the CaCO₃ reacts, the molar gas volume is 24 dm³.
RFM of CaCO₃ = 100, CaO = 56, CO₂ = 44.
Q6.Given 500 cm³ of oxygen gas at RTP, calculate the mass of H₂ gas that completely reacts with it to form water. Give answer to 2 s.f.
2H₂ + O₂ → 2H₂O.
The molar gas volume is 24 dm³.
RFM (Mr) of H₂ = 2
To help you plan your 10 chemistry lesson on: Converting between mass and volume using moles, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 chemistry lesson on: Converting between mass and volume using moles, 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.