Biology · Lesson Worlds
Osmosis: interactive science lab
Change the salt outside and prove that water moves toward the saltier side.
Free · No account required · Runs in your browser
What will you learn?
Water moves toward higher salt. A cell in salty water shrinks. A cell in fresh water swells.
How does the lab work?
Observe the simulation, make a prediction, change a variable, run the experiment, and explain the result. Finish with a challenge that tests your understanding.
You can change: Outside salt. Compare what happens and connect the result to the scientific explanation.
Try a comparison in Osmosis
Start with the lab’s initial settings. Choose one control below, predict the result, and change that control while keeping the others fixed. Record the setting and what you observe before making a second change.
- Outside salt: the lab starts at 2; its available range is 0–8.
For a named starting condition, try Fresh, Room, Brine. A preset can change several settings: check the controls before treating two presets as a one-variable comparison.
Questions to discuss during the activity
- Watch what happens. It holds a size. Watch a cell in ordinary salt.
- Name the cause. Osmosis is water slipping across a membrane toward the saltier side. Saltier outside, water leaves, the cell shrinks. Fresh outside, water enters, it swells. Water chases salt.
- Change something. Raise salt and the cell should shrink. Change outside salt, then soak.
- Guess before you run. If we raise outside salt to 7, the cell will… Guess what will happen, then run to check.
After your comparison, explain how the observations connect to this idea: Water moves toward higher salt. A cell in salty water shrinks. A cell in fresh water swells. Name one condition you held fixed and one feature of the real world this model simplifies. A completed run is a starting point for discussion, rather than proof of mastery.
Who is it for?
Curious learners exploring biology. A parent or teacher can help younger learners read the instructions and discuss the results. Choose by topic and prior knowledge rather than a fixed grade level.
Is this lab free?
Yes. This interactive lab is free without signing in or a paid membership.
No app download is needed; interactive play requires JavaScript and a modern browser.
Use this activity with a learner
Families and educators · choose by prior knowledge
Learning goal: Water moves toward higher salt. A cell in salty water shrinks. A cell in fresh water swells.
Before you begin: Read the controls for Outside salt. Make one prediction before changing a setting.
Check understanding: Ask for one observation, the evidence that supports it, and a question to investigate next.
A simulation simplifies the real world. Explain which conditions stayed fixed; a successful run alone does not demonstrate mastery.
Share Osmosis with your family or class. No account is needed to open the free resource.
Activity and guide by Lesson Worlds. About the platform.
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