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ScienceMixtures and solutions25 min★★ difficulty

Solubility, saturation and diffusion

Sugar disappearing into tea is not a vanishing act. The particles are still there, spread evenly between the water particles.

Part of your national curriculum
  • Chemistry: pure and impure substances: Understand diffusion in terms of the particle model, and the concepts of solutions, solvents, solutes and solubility

Lesson overview

What you'll learn in this lesson

Understand diffusion in terms of the particle model, and the concepts of solutions, solvents, solutes and solubility

Key learning points

  • • The vocabulary, precisely
  • • Saturation
  • • Diffusion

This lesson at a glance

  • 25 minutes
  • 16 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

diffusionparticleconceptssolutionssolvents

Scroll down — the lesson carries on below

Part 1 of 16 · Discover6%
1

Watch & discover

Part 1 of 16

Watch first

Solubility, saturation and diffusion

An English teaching video on this topic from FuseSchool - Global Education. Watch it, then scroll down for the lesson.

In a nutshell

Understand diffusion in terms of the particle model, and the concepts of solutions, solvents, solutes and solubility

2

Learning cycle

Part 2 of 16

Learning cycle 1 of 2

Part 1 · The vocabulary, precisely

A short piece of teaching, then a check to make sure it has landed.

3

Explore the idea

Part 3 of 16

Learn

The vocabulary, precisely

The solute is the substance that dissolves; the solvent does the dissolving; together they form a solution. Solubility is the mass of solute that dissolves in 100 g of solvent at a stated temperature — the temperature matters, so a solubility figure without one is meaningless.

4

Explore the idea

Part 4 of 16

Learn

Saturation

A solution is saturated when no more solute will dissolve at that temperature. Warming the solvent usually raises solubility for solids, so a saturated solution can dissolve more once heated — and may form crystals again as it cools.

5

Quick check

Part 5 of 16

Quick check

In salty water, what is the solute?

6

Quick check

Part 6 of 16

Quick check

Why must a solubility value state a temperature?

7

Reset break

Part 7 of 16

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
8

Learning cycle

Part 8 of 16

Learning cycle 2 of 2

Part 2 · Diffusion

A short piece of teaching, then a check to make sure it has landed.

9

Explore the idea

Part 9 of 16

Learn

Diffusion

Particles in liquids and gases move randomly and spread from where they are crowded to where they are not. No stirring is needed. Diffusion is faster in gases than liquids, and faster when warmer, because the particles move more quickly.

10

Quick check

Part 10 of 16

Quick check

What is a saturated solution?

11

Quick check

Part 11 of 16

Quick check

Why does diffusion happen faster when warmer?

12

Explore the idea

Part 12 of 16

Worked example

Worked example: crystals in the bottom of a jar

Hot water dissolves 200 g of a salt; the jar is left overnight and crystals appear. Explanation: solubility fell as the solution cooled, so the solution became saturated and the excess solute could no longer stay dissolved. Mass is conserved — the crystals were always in the jar, just dissolved.

13

Challenge round

Part 13 of 16

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

14

Challenge round

Part 14 of 16

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

____ is faster in gases than liquids, and faster when warmer, because the particles move more quickly.

15

Mastery quiz

Part 15 of 16

Marked quiz

End of lesson quiz: Solubility, saturation and diffusion

4 questions, marked with the reasoning shown. No timer.

  1. 1. In salty water, what is the solute?

  2. 2. Why must a solubility value state a temperature?

  3. 3. What is a saturated solution?

  4. 4. Why does diffusion happen faster when warmer?

16

Lesson round-up

Part 16 of 16

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 16 · Watch & discover

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    Understand diffusion in terms of the particle model, and the concepts of solutions, solvents, solutes and solubility

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