Balancing equations
I can balance chemical equations, and explain why it is important to ensure symbol equations are balanced.
- Year 10
- OCR
Balancing equations
I can balance chemical equations, and explain why it is important to ensure symbol equations are balanced.
Lesson details
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.
Equipment
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.
Q3.Match the substance to the correct state symbol.
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.
