Preview · the opening missionRead this to the class:
A family made a salad for a picnic and salted it in the morning. By lunch, the lettuce was limp and there was water in the bottom of the bowl. Nobody had added any water. Your team's job: find out where the water came from, and what it tells us about the cells in a plant.
Teams of three, with rotating jobs: Lead (handles the strips), Measurer (uses the scale and ruler), Recorder (writes and calculates).
Look inside the PDF
Sample pages, stamped “preview”. The download is the clean, full lesson.
In the full lesson PDF
- Predict (5–10 min)
- Hunt (20 min)
- Reveal (10–15 min)
- Act (10 min)
- Background for the teacher
- Assessment
- Student sheet
On the student sheet
- My prediction
- Our results
- What we kept the same
- What we saw (onion cells or gummy bears)
- Claim, Evidence, Reasoning
- Exit ticket
US Letter, prints cleanly in black and white. The student sheet is on its own page, ready to photocopy.
Free with an account (any 3 lessons), or US$19 / C$25 for all 4 lessons in this unit.
What students show by the end
- Measures and calculates
- Explains osmosis
- Applies it with CER
From the lesson’s rubric, which scores each one as not yet, getting there or got it.
Questions teachers ask
How long does “How do things get in and out of a cell?” take?
Two sessions: 45 min, then 30 min the next day. Group size: teams of 3.
How much prep does it need?
15 minutes: cut potato strips about 1 cm × 1 cm × 6 cm (1/2 in × 1/2 in × 2 1/2 in), two per cup, and keep them under a damp paper towel. Mix the salty water: 1 tablespoon (about 15 g) of salt in 250 mL (1 cup) of tap water, per team.
What materials do I need?
Large potato, cut into strips by the teacher; clear plastic cups, about 300 mL (10 oz), labelled; table salt; kitchen scale that reads to 0.1 g (to 1 g works, less precisely); ruler with millimetre marks; paper towels and plastic wrap; and 2 more. Cost: about $10 for a class of 30, plus about $15 for a kitchen scale if you don't have one.
Which curriculum standards does it cover?
NGSS (US): MS-LS1-2 (partly). It also matches Ontario Science and Technology, Grade 8.
What’s in the lesson PDF?
A teacher guide that walks you through predict, hunt, reveal, act, background for the teacher and assessment, then a student sheet (“My prediction”; “Our results”; “What we kept the same”; “What we saw (onion cells or gummy bears)”; “Claim, Evidence, Reasoning” and “Exit ticket”) on its own page, ready to photocopy. It’s US Letter and prints cleanly in black and white.
Can I try it for free?
Yes. A free account includes any 3 full lessons of your choice, and this can be one of them. After that, this unit is US$19 (C$25) for all 4 lessons, yours to keep, or every lesson is US$79 (C$109) a year.