• A fully detailed chemical equation should show the state (or phase) of matter that the chemical atoms are in.
• These states are: ∘ Solid, given the symbol (s) ∘ Liquid, given the symbol (l) ∘ Gas, given the symbol (g) ∘ Aqueous, meaning dissolved in water, and given the symbol (aq)
• The information is important for chemists moving from planning a reaction to performing the experiment. Knowing the state of the product helps plan how you can collect the products of the reaction being done.
• Crystals, powder and precipitate are all solid forms.
• Vapour is particles of a substance becoming the gas phase.
• A solution of a chemical would be described as aqueous. For example “a solution of HCl was reacted with a solution of NaOH” in an equation would be shown as “HCl(aq)+NaOH(aq)”
In this lesson, we will learn:
• The four phases that describe chemicals in reaction equations.
• Other key descriptive terms for chemicals in reactions.
• Practical reasons why state symbols are included in a chemical equation.
Building on chemical equations
Read the following experiment notes and write a balanced chemical equation, with state symbols, to describe what is happening.
Phases in chemical reactions
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