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Science lesson plan · 6th grade (Year 7 in England) · 45 minutes

Solutes, solvents and how much will dissolve

Materials and their properties

CCSS NGSS.MS-PS1-2England: KS3 Chemistry: Pure and impure substances

Objective and success criteria

Students will: Solutes, solvents and how much will dissolve.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Dissolving and solutions

Leads to: Choose the right technique to separate a mixture; Concentration in grams per dm³

Materials: A tray of everyday objects, Sorting hoops, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 5 min

  • Quick retrieval from earlier learning (Dissolving and solutions). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Is jelly crystals soluble or insoluble in water? (soluble (dissolves in water) / insoluble (does not dissolve)) → soluble (dissolves in water)Prompt: Imagine stirring it into a glass of water. Would it disappear from view?
  2. 20 g of sugar is dissolved in 500 g of water. What is the mass of the solution, in g? → 520 gPrompt: When something dissolves, does it disappear or is it still there?
  3. Sugar seems to disappear when it dissolves. Where does it go? (It breaks into tiny particles spread through the water / It is destroyed / It turns into water / It floats away as gas) → It breaks into tiny particles spread through the waterPrompt: Taste the water: is the sugar still there?

Hook · 5 min

  • Pass round objects made of different materials and ask why each one was chosen.
  • Share the objective: Solutes, solvents and how much will dissolve. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Which word describes this: the clear mixture made when sugar dissolves in water?
  • Step 1: A solution is the mixture of solute and solvent.
  • Step 2: So the answer is: solution
  • Answer: solution
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Which word describes this: the clear mixture made when sugar dissolves in water? (solution / insoluble / saturated solution / solute) → solutionPrompt: Solute + solvent → solution.
  2. 20 g of salt is dissolved in 100 g of water. What is the mass of the solution, in g? → 120 gPrompt: Does the salt's mass disappear when it dissolves?

You do: independent practice · 10 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. 5 g of salt is dissolved in 200 g of water. What is the mass of the solution, in g? → 205 gPrompt: Does the salt's mass disappear when it dissolves?
  2. Which change would let more sugar dissolve in a cup of water? (using larger sugar lumps / heating the water / cooling the water / stirring more slowly) → heating the waterPrompt: Solubility of most solids changes with temperature.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Dissolving and solutions.
  • Use concrete materials: a tray of everyday objects.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: Choose the right technique to separate a mixture; Concentration in grams per dm³.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-6.

Free lesson plan from eurekami.com/lesson-plan-builder

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Solutes, solvents and how much will dissolve

Name

Date

Score/ 8

  1. Question 1

    Why does sugar dissolve faster in hot tea than in iced tea?

    • A. Particles move faster, so solvent particles break the sugar apart more quickly
    • B. Ice stops sugar existing
    • C. Hot tea has more water in it
    • D. Sugar melts in hot tea

  2. Question 2

    At 20 °C, 36 g of salt dissolves in 100 g of water to make a saturated solution. What mass dissolves in 50 g of water at 20 °C, in g?

    Answerg

  3. Question 3

    Which word describes this: a solution in which no more solute will dissolve?

    • A. saturated solution
    • B. solvent
    • C. solution
    • D. solute

  4. Question 4

    15 g of salt is dissolved in 250 g of water. What is the mass of the solution, in g?

    Answerg

  5. Question 5

    Which word describes this: the clear mixture made when sugar dissolves in water?

    • A. solution
    • B. solvent
    • C. solute
    • D. saturated solution

  6. Question 6

    Nail varnish does not dissolve in water but does dissolve in acetone. What does this show?

    • A. Whether a substance dissolves depends on the solvent
    • B. Nail varnish is a gas
    • C. Acetone is a solute
    • D. Water dissolves everything

  7. Question 7

    At 20 °C, 200 g of sugar dissolves in 100 g of water to make a saturated solution. What mass dissolves in 50 g of water at 20 °C, in g?

    Answerg

  8. Question 8

    At 20 °C, 32 g of potassium nitrate dissolves in 100 g of water to make a saturated solution. What mass dissolves in 50 g of water at 20 °C, in g?

    Answerg

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Answer key: Solutes, solvents and how much will dissolve

  1. 1. A. Particles move faster, so solvent particles break the sugar apart more quickly

  2. 2. 18 g

  3. 3. A. saturated solution

  4. 4. 265 g

  5. 5. A. solution

  6. 6. A. Whether a substance dissolves depends on the solvent

  7. 7. 100 g

  8. 8. 16 g