A word equation is a way of describing a reaction using the chemical names of the reactants and products.

A chemical formula represents a substance using element symbols and the number / ratio of atoms of each element in the substance.

A symbol equation is a way of describing a reaction using the chemical formulae of the reactants and products.

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.

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.

Balancing equations

Combined science

In the Making salts unit, pupils will learn about the production of pure salts, concentration and strength of acids, and what makes acids acidic and how bases can neutralise them.

In the Atomic structure and periodic table unit, pupils learned about atoms, and how the periodic table is ordered, along with the history of both of their major discoveries.

Calculations involving masses

number and ratio of each element in a substance

What does a chemical formula like Na₂O represent?

describes a chemical reaction using chemical names

represents a substance using element symbols and numbers

describes chemical reactions using chemical formulae and state symbols

Match the terms to the correct definitions. 

Identify the reactants' and products' chemical formulae.

Count the initial particles of each type in the reactants and products.

Add coefficients to each substance to add multiples, as required. 

Confirm the final number of particles in the reactants is equal to the products.

Starting with identifying the reactants and products chemical formulae, sort the steps to describe how to balance an equation.

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.

Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)

Cl₂ (l) + KI (aq) → KCl (aq) + I₂ (l)

NaOH (aq) + HNO₃ (aq) → NaNO₃ (aq) + H₂O (l)

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)

Select the correct balanced equation for when propane (C₃H₈) completely combusts to form carbon dioxide and steam.

What elements are present in CaCO₃ and how many atoms are there of each?

Match the substance names and symbol formulae. 

Match the substance to the correct state symbol.

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?

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? 

Br₂ (g) + 2NaI (aq) → 2NaBr (aq) + I₂ (g)

Br₂ (aq) + 2NaI (aq) → 2NaBr (aq) + I₂ (aq)

Br₂ (l) + NaI (aq) → NaBr (aq) + I₂ (l)

Which symbol equation is correct for when bromine displaces iodine from sodium iodide solution?

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