Chemical reactions: precipitation
Lesson details
Learning outcome
I can describe what happens during precipitation reactions, and write chemical equations to show these.
Key learning points
- Precipitation reactions occur when two solutions combine to form an insoluble solid.
- The appearance of a precipitate is evidence that a chemical reaction has occurred.
- Precipitation reactions are important in water treatment, to remove unwanted substances from water.
- Precipitation reactions are used in qualitative analysis, to identify the presence of certain substances in a solution.
Keywords
Precipitation - The process where a precipitate is formed.
Precipitate - An insoluble solid formed when two solutions react together.
Aqueous solution (aq) - Formed when a substance is dissolved in water.
Insoluble - A way of describing a substance that will not dissolve in a particular solvent.
Chemical qualitative analysis - A chemical test that confirms the presence of a substance, it does not tell you how much of the substance is present.
Common misconception
Pupils can struggle to understand that a solid is not always a large piece of a substance.
Show visually the difference between a transparent coloured solution e.g. copper sulfate solution and a coloured precipitate solution. Practice describing the difference between a white precipitate and a transparent colourless solution.
Teacher tip
A live demonstration of the lead iodide reaction is good to use as a hook to the lesson. When left for a while it will settle to the bottom of the beaker or the teacher can demonstrate filtration of the products showing a solid is formed.
Equipment
Lead nitrate, potassium iodide, beakers, filtration kit: conical flask, filter paper, funnel, solutions containing CU²⁺, Fe²⁺, Fe³⁺, Ca²⁺, Al³⁺, sodium hydroxide, test tubes and rack.
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.What does the arrow (→) in a chemical equation represent?
Q2.Match each description with the correct state symbol:
(s)
(l)
(g)
(aq)
Q3.Solubility refers to the ability of a substance to in water.
Q4.True or false? When a substance dissolves in ethanol it will form an aqueous solution.
Q5.Which of the following is true about solubility?
Q6.In chemistry, what does "precipitation" refer to?
Assessment exit quiz
6 Questions
Q1.What is a precipitate?
Q2.Why are precipitation reactions used in qualitative analysis?
Q3.A substance that will not dissolve in a particular solvent is described as .
Q4.Which term describes a chemical test that confirms the presence of a substance without measuring its quantity?
Q5.An solution is formed when a substance is dissolved in water.
Q6.A precipitate is an insoluble in a solution.
To help you plan your 8 science lesson on: Chemical reactions: precipitation, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 8 science lesson on: Chemical reactions: precipitation, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
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