Determining an equation experimentally: magnesium oxide
Lesson details
Learning outcome
I can describe a safe experiment to calculate the reacting molar ratios for the oxidation of magnesium.
Key learning points
- Heating magnesium in a crucible will react it with oxygen.
- The crucible must be opened periodically to ensure enough oxygen enters the vessel to completely oxidise the magnesium.
- Opening the crucible too much will cause mass/product loss.
- Safety precautions should be taken when burning magnesium because of the bright light produced.
- The stoichiometry for a reaction can be calculated given experimental data.
Keywords
Limiting reactant - the reactant that completely reacts, thereby determining the maximum amount of product that can be formed in a chemical reaction. All other reactants will be present in excess
Ratio - used to determine the size of one quantity in relation to another
Stoichiometry - the molar ratio of the reactants and products in a chemical reaction
Mole - A 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.
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 equation
Common misconception
Pupils sometimes struggle to understand that 'heating to constant mass' takes time and multiple measurements.
Link the idea that atoms rearrange during a reaction and that for all atoms of a substance to be oxidised, enough oxygen must be present. If the product measurements show a 'constant mass' we can be confident that complete oxidation has occurred.
Teacher tip
This lesson presents a fantastic opportunity to bring together multiple aspects of the topic; types of reactions, conservation of mass, moles, limiting reactants, practical skills, equipment choice, etc. Opportunities to adapt it to the needs of the class/provide extension activities is extensive!
Equipment
Mg strip, crucible + lid, clay triangle, tripod, Bunsen burner, heatproof mat, tongs, balance.
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Match the following terms to the correct definition.
Reaction in which oxygen atoms bond to the elements of the reactants.
The reactant that completely reacts during a reaction.
A reactant that remains at the end of a reaction.
How many moles of each chemical we need to react to make the products.
Q2.True of false? Combustion is an example of an oxidation reaction.
Q3.Which of the following equations describes an oxidation reaction?
Q4.The formula for glucose is C₆H₁₂O₆. Which of the following statements about glucose are correct?
Q5.Which of the following are examples of oxidation reactions?
Q6.What is the ratio of oxygen to carbon dioxide in the following equation?
CH₄ + 2O₂ → CO₂ + 2H₂O
Assessment exit quiz
6 Questions
Q1.Match the following terms to the correct definition.
The molar ratio of the reactants and products in a chemical reaction.
The unit of substance.
Substance that completely reacts during a reaction.
The mass remains the same.
Q2.Which of the following is an example of a closed environment?
Q3.Which of the following are advantages of using a crucible and lid to heat magnesium?
Q4.Use the following information to calculate the mass of oxygen that reacted with the magnesium to form magnesium oxide. Mass of magnesium = 4.78 g; mass of magnesium oxide = 7.56 g.
2Mg + O₂ → 2MgO
Q5.When magnesium is heated in a crucible the lid is occasionally opened. This makes sure the oxygen ...
Q6.Calculate the amount of magnesium oxide in 7.56 g. Relative atomic masses: Mg = 24; O = 16.
To help you plan your 10 combined science lesson on: Determining an equation experimentally: magnesium oxide, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 combined science lesson on: Determining an equation experimentally: magnesium oxide, 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 combined science lessons from the Calculations involving masses unit, dive into the full secondary combined science curriculum, or learn more about lesson planning.