S, L, G and aq

The idea

The physical states of reactants and products are written beside their formulae as (g) gas, (l) liquid, (aq) aqueous, meaning a solution in water, and (s) solid; usually they are included only when necessary.

What state is it in?

Look at 3Fe + 4H₂O → Fe₃O₄ + 4H₂. It does not tell you whether the iron is a lump or a powder, or whether the water is a liquid or steam.

How could an equation say what state each substance is in?

• By writing a small letter in brackets after the formula
• By colouring the formula
• It cannot

Add the symbols

Tap a tile, then tap the empty box after the formula.

Four symbols

Physical states are written beside the formulae: (g) gas, (l) liquid, (aq) aqueous (a solution in water), (s) solid. Usually they are included only when necessary.

3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

• Symbol | Meaning | Example
• (s) | solid | Fe(s)
• (l) | liquid | H₂O(l)
• (g) | gas | H₂(g)
• (aq) | aqueous: dissolved in water | Ca(OH)₂(aq)

Notes

The physical states of reactants and products are written beside their formulae as (g) gas, (l) liquid, (aq) aqueous, meaning a solution in water, and (s) solid; usually they are included only when necessary.

Check yourself

What does (aq) mean?

In Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) + 2NaCl(aq), which product is a solid?

Why is H₂O written as (g) in 3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)?

• A solution in water — correct. Yes! Aqueous means dissolved in water.
• Solid. Solid is (s).
• A gas. Gas is (g).
• NaCl. NaCl(aq) is dissolved in water.
• BaSO₄ — correct. Yes! It is marked (s). It does not dissolve.
• Na₂SO₄. Na₂SO₄ is a reactant, and it is (aq).
• Because water is always a gas. At room temperature water is a liquid, (l). Here it is steam.
• Because it is a reactant. The state does not depend on being a reactant.
• The water is used in the form of steam — correct. Yes! The book says (g) shows water is used as steam.