Balancing equations
Lesson details
Learning outcome
I can balance chemical equations, and explain why it is important to ensure symbol equations are balanced.
Key learning points
- All the atoms in the reactants of a chemical reaction are reorganised to form all the products of the reaction.
- There must be an equal number of each type of atom on both the reactant and product side of the equation.
- Chemical formulae cannot be altered to balance a reaction equation; only coefficients can change.
- Atoms cannot be created or destroyed. During a chemical reaction, atoms are simply rearranged into products.
Keywords
Word equation - A word equation represents a chemical reaction using the chemical names of the reactants and products.
Chemical formula - A chemical formula represents a substance using element symbols and the number / ratio of atoms of each element in the substance.
Symbol equation - A symbol equation represents a chemical reaction using the chemical formulas of the reactants and products.
Balanced symbol equation - A balanced symbol equation uses coefficients to ensure that the number of atoms of each element is equal on both sides of the equation.
Coefficient - A coefficient is the number placed in front of a chemical formula to balance an equation; it multiplies all the atoms in the formula and shows the ratio of substances in a reaction.
Common misconception
Pupils sometimes think that chemical formulae can be changed to balance atoms.
Put boxes around each formula in the equation / pretend there is a bucket of pre-made molecules which they can use to balance the number of atoms on each side. Stress that it takes perseverance and practice before equations are balanced.
Teacher tip
Use a 'box / bubble method' or use molymods / bricks to to balance equations. Pupils are only able to use what already exists in the reaction equation in order to balance it.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.What elements are present in CaCO₃ and how many atoms are there of each?
Q2.Match the substance names and symbol formulae.
MgO
AlI₃
CuCO₃
NaOH
K₂SO₄
SrCl₂
Q3.Match the substance to the correct state symbol.
H₂O (l)
H₂O (s)
H₂O (g)
NaCl (aq)
Hg (l)
He (g)
Q4.The chemical formula for magnesium oxide is MgO. In a chemical symbol equation, how would you amend this to provide twice as many Mg and O particles?
Q5.When 12.2 g of iron reacted with an unknown mass of sulfur, 20.6 g of a product was formed. What was the mass of the sulfur?
Q6.Which symbol equation is correct for when bromine displaces iodine from sodium iodide solution?
Assessment exit quiz
6 Questions
Q1.What does a chemical formula like Na₂O represent?
Q2.Match the terms to the correct definitions.
describes a chemical reaction using chemical names
represents a substance using element symbols and numbers
describes chemical reactions using chemical formulae and state symbols
Q3.Starting with identifying the reactants and products chemical formulae, sort the steps to describe how to balance an equation.
Q4.A coefficient is the number placed in front of a chemical formula to balance an equation; it all the atoms in the formula and shows the ratio of substances in a reaction.
Q5.Determine which reactions are balanced.
Q6.Select the correct balanced equation for when propane (C₃H₈) completely combusts to form carbon dioxide and steam.
To help you plan your 10 combined science lesson on: Balancing equations, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 combined science lesson on: Balancing equations, 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.