Concentration In Solutions

Overview

Students build on prior learning about solutes, solvents, solutions and the effect of heat on dissolving. They develop a Year 7 understanding of concentration and dilution by comparing the amount of solute per fixed volume, using everyday examples and a guided 20-minute web quest.

Learning intentions

Students will:

• Explain concentration as the amount of solute in a given volume of solution.
• Compare solutions as more concentrated or more dilute.
• Describe how adding solute, adding solvent or removing solvent changes concentration.
• Use evidence from examples and research to communicate a scientific explanation.

Success criteria

• I can identify the solute, solvent and solution in an example.
• I can explain why two solutions with the same volume may have different concentrations.
• I can describe what happens during dilution.
• I can use the words concentrated, dilute, solute, solvent and volume accurately.

Curriculum links

• Science understanding: properties and behaviours of substances, including solutions and the relationship between solute, solvent and solution.
• Science inquiry: locating, interpreting and evaluating information from observations and reliable digital sources.
• Science as a human endeavour: applying scientific ideas to familiar contexts such as drinks, medicines and cleaning products.
• Science communication: representing and explaining scientific ideas using appropriate terminology.

Lesson structure (95 minutes)

1. 0–8 minutes – Engage: “Which drink is stronger?” Open with the hook and lesson goals. Show two identical cups labelled A and B: A contains one spoon of cordial in 200 mL of water; B contains three spoons in 200 mL. Students vote on which is more concentrated and justify their choice. Clarify that concentration is not the same as colour, temperature or how quickly a substance dissolves.

2. 8–25 minutes – Explicit teaching and modelling Use the concentration explanation and visual models to define:

• Solute: the substance that dissolves.
• Solvent: the substance that does the dissolving.
• Solution: the evenly mixed result.
• Concentration: the amount of solute in a stated volume of solution. Model equal-volume examples using counters or diagrams: 1, 2 and 4 teaspoons of sugar in 200 mL of water. Explain that more solute in the same volume means more concentrated. If the amount of solute stays the same but the volume increases, the solution becomes more dilute.

3. 25–35 minutes – Guided examples: changing concentration Display the “concentration changes” table in worked examples and discussion prompts. In pairs, students predict the result of each change before sharing:

• Add sugar to the same volume of water: more concentrated.
• Add water to the same amount of cordial: more dilute.
• Evaporate some water: more concentrated.
• Add equal amounts of water and cordial: concentration may stay similar. Emphasise that dilution means adding solvent to reduce concentration; it does not mean the solute disappears. Briefly connect this to juice, seawater, sports drinks and medicines.

4. 35–55 minutes – Guided 20-minute web quest Distribute the concentration web quest and response sheet and open the web quest instructions and research questions. Students work in pairs, with one device per pair where possible. They use teacher-approved websites or a school search tool, not unrestricted browsing, to answer:

• What is concentration in a solution?
• What is dilution?
• Find one household or environmental example of a concentrated solution and one dilute solution.
• Explain how to dilute cordial safely and fairly.
• Why can seawater be described as a solution? Students record the website or organisation name, one useful fact and a rewritten explanation rather than copying. The teacher checks vocabulary and redirects students who confuse dissolving speed with concentration.

5. 55–70 minutes – Apply and explain Pairs complete the comparison tasks on the concentration comparison questions. They rank three illustrated solutions from most concentrated to most dilute and explain their reasoning using “amount of solute per given volume”. Include a challenge: Solution X has 2 g of salt in 100 mL; Solution Y has 4 g in 200 mL. Students decide whether the concentrations are equal and explain why. Discuss answers, accepting diagrams or spoken explanations before requiring a written scientific sentence.

6. 70–78 minutes – Whole-class consolidation Use the misconception check and summary diagram. Students respond on mini-whiteboards to statements such as “A darker solution is always more concentrated” and “Adding water dilutes a solution”. Correct misconceptions and jointly construct the sentence: “Concentration depends on the amount of solute compared with the volume of solution.”

7. 78–95 minutes – End-of-lesson check Students complete the individual check-in on the written response and ten-question quiz silently. It includes short responses:

• Define concentration in your own words.
• Explain how to dilute 100 mL of cordial.
• Compare 1 g in 50 mL with 1 g in 100 mL.
• Identify one real-life example of dilution. It also includes approximately 10 multiple-choice questions covering solute, solvent, solution, concentration, dilution, equal-volume comparisons and common misconceptions. Collect responses for diagnostic marking. Finish with the plenary answer review and key message if time permits.

Resources

• the concentration teaching deck
• the concentration web quest and assessment worksheet
• 20 student devices, one per pair where possible
• Teacher-approved websites or school search platform
• Mini-whiteboards or scrap paper
• Transparent cups, water, teaspoons and coloured counters or beads for modelling
• Board and markers
• Timer
• Printed vocabulary support cards or displayed word bank

Assessment

• Monitor pair explanations during modelling and the web quest, noting correct use of solute, solvent, solution, concentration and dilution.
• Check web quest responses for selecting relevant information and rewriting it accurately.
• Mark the final written responses and 10 multiple-choice questions to identify misconceptions and plan reteaching.

Differentiation

• Provide a visual word bank, sentence stems and labelled diagrams: “The solution is more concentrated because it has ___ solute in the same ___.”
• Pair students strategically; allow oral answers, text-to-speech or a scribe for students requiring adjustments.
• Give EAL learners everyday examples, translated key terms where available and a reduced research question set with teacher-selected pages.
• Extend confident students by asking them to compare equal concentrations with different volumes or explain why concentration can change when solvent evaporates.