Before the first slot
Read Science Cards A–H and the staff key. Have paper, a pencil, a ruler if convenient, and a basic calculator for ratios, means and percentages. No purchases, devices or internet connection are required. Draw a two-column boundary and a cube outline on paper, or simply read the descriptions. Colour and fine drawing are optional.
Choose a private or paired response arrangement with the learner. They can write, type, speak, use AAC, annotate, or direct someone to place labelled cards. Read out all labels and numbers if helpful. Keep their biological explanation and calculation visible in the chosen mode. A support person records the learner's choices without completing the reasoning. Offer extra time without making speed a success criterion. A spoken source reading does not establish independent reading; no independent reading score is intended here.
The first bridge asks about a cell membrane, an organelle and a model limit. If those ideas are insecure, use the supplied Card A and the first two worked contexts before moving on. Allow an extra locally scheduled session if needed; do not compress the remaining teaching to maintain a calendar label.
The materials to hand out
Use Science Cards A–E for slots 11–15; add F–H for slots 16–20. Keep worked solutions with staff until an example has been attempted or intentionally modelled. For slot 15, hand out only E first; for slot 20, only F first. Collect the first response before giving the matching later information from checks/later. The later sheet has its own complete task. Keep all keys, rubric exemplars and unused rechecks out of the first encounter. These are teaching checks, not secure examinations: public versions would remain discoverable.
Choose an optional complete print aid, or use its full text alternative. Each aid PDF has all its named teaching pages. Deliver the separate PORTABLE-NOTICE.pdf with every offline aid set; it is a companion, not embedded in the teaching PDF. Hand out first and later check aids at different times. The chooser identifies each role, page count and complete notice link.
Keep the model conditions visible
Use concentration alone to predict neutral-solute movement only when the card permits that substance through the specified route and gives a usable gradient. For charged ions, a concentration difference alone cannot settle net passive direction: the electrical component also matters. Our pump cards explicitly supply the energy-coupled direction. Do not teach that every channel needs ATP or that every protein-mediated movement is active.
All simple osmosis cases specify a solute that cannot cross, water that can cross, equal temperature and equal initial hydrostatic pressure. Predict the initial net water movement. Do not promise a final volume or universal plant-cell outcome. When pressure information becomes unknown, do not retain a concentration-only prediction as certain. Real cells have multiple solutes, changing pressures, walls and regulatory processes.
The cubes are geometric cell models, not measured cells. Here the layer starts at d_start = 0 mm when t_start = 0 min. The change in depth divided by elapsed time, Δdepth/Δtime = (d_end − d_start)/(t_end − t_start), is a supplied model's average front speed, not a universal biological diffusion law. The shell fraction at one time is a geometric penetration proxy. It is not a measurement of molecule flux or an intrinsic diffusion coefficient. A mean from three invented repeats teaches arithmetic and discussion of variability; it is not empirical evidence.
Practical preparation and the next actual inquiry
This paper slice needs paper only. Do not culture microorganisms, handle biological fluids, taste materials, alter food intake, use stains or chemicals, or ask for health information. No home experiment is requested. Home invitations offer explanation, paper modelling and claim revision.
A qualified teacher may later choose a school-approved actual or genuine virtual diffusion investigation as part of the wider course. Before that work, establish a research question, independent and dependent variables, relevant controlled conditions, a reproducible measurement definition, independent repeats, instrument resolution, a recording table, risk and disposal procedures, and the access arrangement. Decide whether the dependent measure is time to a stated endpoint, amount crossing per time, front depth, or fraction penetrated. These cannot be silently substituted for each other. Record the actual apparatus or named virtual system and actual observations separately from supplied examples. Repeated readings of one sample are not independent biological repeats. Teacher planning alone does not mean the investigation occurred.
For this paper slice, the evidence record is short: task, first or later response, mode/support, one observed strength, one next teaching move. If a learner chooses a route with a supplied partial table, record that support. Do not turn a desk checklist into a biological practical-completion record.
Time and feedback
Ordinary slots use 3 minutes to launch, 6 to model, 7 for guided work, 10 for a selected route, 5 to discuss and 4 for the exit: 35 minutes. Check slots use their own 35-minute sequence. Times are suggestions, not deadlines for learners.
After each exit, choose the smallest useful next move. For example, have the learner redraw the gradient arrow with labels, calculate area and volume in separate lines, or distinguish an average front speed from a fractional-volume comparison. Return to the same idea using a different supplied case. Reserve rechecks until after feedback and a delay. A correct supported response is useful evidence about that response, not full independent mastery.