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.
• A fully detailed chemical equation should show the state (or phase) of matter that the chemical atoms are in. This is meant to tell you the arrangement of the atoms of the reactants when they engage in the chemical reaction.
• 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. ∘ For example, a desired product dissolved in solution would need to be evaporated, and a solid product would need to be filtered to help isolate it.
• There are some common chemical ‘forms’ of some states - crystals, powder and precipitate are all solid forms. ∘ Vapour is particles of a substance becoming a gas.
• 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)”
Building on chemical equations
Write full chemical equations using information from descriptions of laboratory experiments.
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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