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States of matter for Edexcel A-level Chemistry
This page covers the following topics:
1. State symbols
When writing chemical equations, state symbols are used to indicate which physical state each compound is in. They are written in brackets in subscript after a formula by using (s) for solid, (l) for liquid, (g) for gas and (aq) for aqueous, that is, dissolved in a solution. For example, C(s) + O₂(g) → CO₂(g). Some examples of how these symbols can be used are provided below.
⋅ compounds dissolved in a solution → (aq)
⋅ water in a neutralisation reaction → (l)
⋅ insoluble precipitate → (s)
⋅ gas insoluble in a solution → (g)
⋅ most metals at room temperature → (s)
⋅ most pure salts at room temperature → (s)
1
Include the state symbols to the following equation:
CH₄ + 2O₂ → CO₂ + 2H₂O.
All of the reactants and products participating in this reaction are gases, including water that becomes gas due to the reaction being exothermic. However, a liquid state may be assigned to water while, for example, considering enthalpy.
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
2
Provide a letter that is used for the state symbol in a chemical reaction equation for silver bromide precipitate.
insoluble precipitate → (s)
s
3
Rewrite this chemical reaction equation to include state symbols.
2Al + 3Cl₂ → 2AlCl₃
⋅ Aluminium metal is solid.
⋅ Chlorine naturally exists as gas.
⋅ Aluminium chloride has nowhere to dissolve, it remains solid.
2Al(s) + 3Cl₂(g) → 2AlCl₃(s)
4
Two compounds have reacted to neutralise each other and during this reaction water has been produced. What is the letter used for the state symbol in an equation for the water produced?
water in a neutralisation reaction → (l)
l
5
Rewrite the provided chemical equation to include state symbols. Assume that water is applied in this reaction as steam.
Mg + 2H₂O → Mg(OH)₂ + H₂
⋅ Magnesium metal is solid.
⋅ Water steam is gas.
⋅ Magnesium hydroxide is somewhat soluble in water.
⋅ Hydrogen gas is not soluble in water.
Mg(s) + 2H₂O(g) → Mg(OH)₂(aq) + H₂(g)
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