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
- 20 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 20
Visual introductionPicture this
Solubility, saturation and diffusion
Sugar disappearing into tea is not a vanishing act. The particles are still there, spread evenly between the water particles.
In a nutshell
Understand diffusion in terms of the particle model, and the concepts of solutions, solvents, solutes and solubility
Learning cycle
Part 2 of 20
Learning cycle 1 of 2
Part 1 · The vocabulary, precisely
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 20
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.
Reset break
Part 4 of 20
Pause
That's sitting 1 of 5 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.
Explore the idea
Part 5 of 20
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.
Quick check
Part 6 of 20
Quick check
Part 7 of 20
Reset break
Part 8 of 20
Pause
That's sitting 2 of 5 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.
Learning cycle
Part 9 of 20
Learning cycle 2 of 2
Part 2 · Diffusion
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 20
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.
Quick check
Part 11 of 20
Reset break
Part 12 of 20
Pause
That's sitting 3 of 5 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.
Quick check
Part 13 of 20
Explore the idea
Part 14 of 20
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.
Challenge round
Part 15 of 20
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
Reset break
Part 16 of 20
Pause
That's sitting 4 of 5 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.
Challenge round
Part 17 of 20
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.
Challenge round
Part 18 of 20
Game · Recall cards
What causes diffusion?
Card 1 of 4
Mastery quiz
Part 19 of 20
Marked quiz
End of lesson quiz: Solubility, saturation and diffusion
4 questions, marked with the reasoning shown. No timer.
1. What causes diffusion?
2. In a solution of salt water, what is the solute?
3. What generally happens to the solubility of a solid as temperature rises?
4. Diffusion is fastest in
Lesson round-up
Part 20 of 20
Lesson round-up
Ready when you are
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Understand diffusion in terms of the particle model, and the concepts of solutions, solvents, solutes and solubility