2026–27 · Backup lesson · Winter 2027
Compare Dissolving and Settling in Water
Adult extension of: What Dissolves in Water?
Unscheduled alternative · available resource
Investigate equal small samples of salt, sugar, and clean sand in measured water without tasting any mixtures. Use the results to distinguish dissolving from settling and to explain why a clear-looking liquid is not necessarily pure or safe.
Curriculum skill focus: Prediction, comparison, observation, material properties
01 · Learning
Objectives
- Keep water volume, sample amount, and mixing time similar.
- Distinguish visible settling from a material becoming evenly dispersed as a solution.
- Explain why appearance alone cannot establish drinking-water safety.
02 · Preparation
Materials
Clearly labeled salt, sugar, and clean sand for experiment use only; clear non-glass cups; room-temperature water; measuring spoon and jug; separate stirrers; timer; labels; tray; optional paper filter and catch cup.
03 · Practice
Adult project
- 1
Identify the three materials and mark all cups experiment only. Predict what each will do in water, choose handling or observation roles, and state that tasting is not part of the investigation even when ingredients began as foods.
- 2
Measure equal water volumes into labeled cups and equal small sample amounts with clean separate tools. Use an amount of salt or sugar comfortably below its likely saturation limit to make the intended comparison practical.
- 3
Add one material to each cup and stir each for the same timed interval. Observe remaining grains, cloudiness, and any material on the bottom without assuming that lack of visible grains means the material ceased to exist.
- 4
Let the cups stand for the same period, then compare them again. Record whether visible particles settle, remain, or are no longer individually visible, and note that an uncertain result may need longer mixing or a smaller sample.
- 5
If useful, pass a small portion through a paper filter and compare visible residue. Explain that a simple paper filter may retain sand but does not remove dissolved salt or sugar; the result is not a drinking-water treatment test.
- 6
Create the mixture record and connect it to following product mixing directions or recognizing sediment in a watering container. Dispose of sand into an appropriate solid-waste container, clean the cups, and keep all samples out of food service.
Evidence & interpretation
What the investigation shows
Dissolving disperses particles of a solute through a solvent; the substance remains present. Solubility depends on the substance and conditions, and enough added material can exceed the amount that will dissolve.
Practical connection
Why this work matters
Knowing the difference between a solution and a suspension supports careful mixing and avoids false assumptions about clear water.
Participation by choice
Individual access options
- Use premeasured samples and a large stirrer, or direct a partner’s stirring and timing.
- Observe large clear cups against a plain background or review magnified images with spoken descriptions.
- Choose a dry recording role, compare two materials instead of three, or decline powder and water contact while retaining the prediction role.
Review & transfer
Reflect on the work
- What evidence helped you distinguish dissolving from settling?
- Why would clear appearance or paper filtering not prove water is safe to drink?