Starter quiz
- What elements are present in CaCO₃ and how many atoms are there of each?
- calcium (1) and cobalt (3)
- calcium (3), carbon (3) and oxygen (3)
- carbon (1), actinium (1) and oxygen (3)
- calcium (1), carbon (1) and oxygen (3) ✓
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- Match the substance names and symbol formulae.
- magnesium oxide⇔MgO ✓
- aluminium iodide⇔AlI₃ ✓
- copper carbonate⇔CuCO₃ ✓
- sodium hydroxide⇔NaOH ✓
- potassium sulfate⇔K₂SO₄ ✓
- strontium chloride⇔SrCl₂ ✓
- Match the substance to the correct state symbol.
- water⇔H₂O (l) ✓
- ice⇔H₂O (s) ✓
- steam⇔H₂O (g) ✓
- dissolved sodium chloride⇔NaCl (aq) ✓
- mercury at room temperature⇔Hg (l) ✓
- helium at room temperature⇔He (g) ✓
- 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?
- Mg₂O₂
- 2Mg₂O
- 2MgO ✓
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- 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?
- 8.4 g ✓
- 32.8 g
- 12.2 g
- 6.1 g
- 10.3 g
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- Which symbol equation is correct for when bromine displaces iodine from sodium iodide solution?
- Br (l) + NaI (aq) → NaBr (aq) + I (l)
- Br₂ (g) + 2NaI (aq) → 2NaBr (aq) + I₂ (g)
- Br₂ (aq) + 2NaI (aq) → 2NaBr (aq) + I₂ (aq) ✓
- Br₂ (l) + NaI (aq) → NaBr (aq) + I₂ (l)
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Exit quiz
- What does a chemical formula like Na₂O represent?
- chemical name of a substance
- number and ratio of each element in a substance ✓
- physical state of a substance
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- Match the terms to the correct definitions.
- word equation⇔describes a chemical reaction using chemical names ✓
- chemical formula⇔represents a substance using element symbols and numbers ✓
- symbol equation⇔describes chemical reactions using chemical formulae and state symbols ✓
- Starting with identifying the reactants and products chemical formulae, sort the steps to describe how to balance an equation.
- 1⇔Identify the reactants' and products' chemical formulae.
- 2⇔Count the initial particles of each type in the reactants and products.
- 3⇔Add coefficients to each substance to add multiples, as required.
- 4⇔Confirm the final number of particles in the reactants is equal to the products.
- 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.
- 'multiplies' ✓
- Determine which reactions are balanced.
- Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g) ✓
- CaCO₃ (s) → CaO (s) + CO₂ (g) ✓
- Cl₂ (l) + KI (aq) → KCl (aq) + I₂ (l)
- NaOH (aq) + HNO₃ (aq) → NaNO₃ (aq) + H₂O (l) ✓
- 2K (s) + O₂ (g) → 2K₂O (s)
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- Select the correct balanced equation for when propane (C₃H₈) completely combusts to form carbon dioxide and steam.
- C₃H₈ (g) + O₂ (g) -> CO₂ (g) + H₂O (g)
- C₃H₈ (g) + 2O₂ (g) -> 3CO₂ (g) + 4H₂O (g)
- C₃H₈ (g) + 5O₂ (g) -> 3CO₂ (g) + 4H₂O (l)
- 2C₃H₈ (g) + 7O₂ (g) -> 6CO (g) + 8H₂O (g)
- C₃H₈ (g) + 5O₂ (g) -> 3CO₂ (g) + 4H₂O (g) ✓
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Worksheet
Presentation
Video
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.
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.
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.