Domain: Natural Science — Chemistry
Target concept: The Reaction of Iodine with Starch Compared to Cellulose (Effects of Polymer Structure on Binding)

Video generation prompt: Two transparent beakers are placed side by side: one contains a starch suspension, and the other contains cellulose fibers; iodine solution is added to both.

Evaluation guide:
(i) Target concept: Differential iodine-induced coloration due to structural complementarity between iodine and amylose helices versus absence thereof in cellulose.
Minimum mechanism: Iodine must physically contact starch to trigger blue-black complex formation; cellulose must remain physically distinct (non-dissolved, non-gelatinized) and structurally inert to iodine under ambient conditions.
(ii)Storyline: Frame 0–2: Static shot revealing two side-by-side transparent beakers: left contains cloudy starch suspension, right contains discrete cellulose fibers; no iodine yet. Frame 3–5: Iodine solution visibly dispensed into left beaker → immediate, uniform blue-black color development confined within suspension. Frame 6–8: Iodine solution dispensed into right beaker → no color change; fibers retain original appearance and texture. Frame 9–10: Final stable contrast held (blue-black starch vs. unchanged cellulose) under consistent lighting and fixed viewpoint. Visibility constraint: Entire beaker bodies, liquid/fiber interfaces, and iodine contact zones must remain fully in-frame and unoccluded at all times; no cutaways, inserts, or text overlays.

Manual:
Experimental Procedure
1. Place two transparent beakers side-by-side on a neutral background.
2. Fill left beaker with starch suspension (opaque white/cloudy liquid).
3. Fill right beaker with cellulose fibers (dry, fibrous, off-white solid).
4. Add iodine solution (amber/brown liquid) to both beakers simultaneously or sequentially.
Observation of Experimental Phenomena
- Starch suspension turns instantly blue-black upon iodine contact.
- Cellulose fibers show no color change — remain off-white/brown and fibrous.
Summary of Experimental Principles
Iodine forms polyhalide complexes with amylose helices in starch, producing blue-black color; cellulose lacks helical structure and does not bind iodine, so no color change occurs — demonstrating how polymer conformation dictates molecular binding.

Prompt Grounding rubric:
level_1: Fewer than two containers are shown, or the containers shown are not clear glass so nothing inside can be seen; neither a cloudy starch suspension nor cellulose fibers can be identified in any container; iodine solution never appears being poured into anything; the two containers are never shown together in the same shot side by side; instead only one appears at a time or one is stacked behind the other.
level_2: Two containers appear, but at least one is opaque or tinted so its contents are hidden; only one of the two substances (the starch suspension or the cellulose fibers) is recognizable, while the other container's contents are missing or unclear; iodine solution is poured into only one of the two containers, or is never poured at all; the containers are positioned so far apart, overlapping, or oddly cropped that they cannot be compared directly.
level_3: Two clear glass beakers stand next to each other; one holds a cloudy starch suspension and the other holds a light-colored solid meant to be cellulose, but its stringy, fibrous texture is not clearly visible: it could pass for a fine powder or a soft gel rather than distinguishable fibers; iodine solution is dispensed into both beakers, though the order of the two additions is confusing or hard to follow (e.g., it's unclear which beaker received iodine first or whether both actually got it).
level_4: Two clear glass beakers remain side by side without changing position; the left beaker holds a visibly cloudy, opaque starch suspension and the right beaker holds a solid mass of fine, separate cellulose fibers (clearly not powder, gel, or a dissolved substance); iodine solution is added to the starch beaker and then to the cellulose beaker (or vice versa) in a sequence that is easy to follow; neither substance is substituted for the other (no flour-like powder standing in for starch, no dissolved pulp standing in for cellulose); no beaker, substance, or the iodine bottle is missing, duplicated, or removed from the frame.
level_5: All 4-point conditions are met, and in addition: both beakers keep the same clear, undistorted glass appearance before iodine is added; the iodine poured into each beaker looks like the same amber liquid, added in a similar pour or drip style; no hand, prop, or camera framing ever blocks either beaker or its contents at any moment; the camera holds one steady, front-facing view of both beakers together for the whole clip, with no panning, tilting, zooming, or repositioning.

Scientific and Causal Correctness rubric:
level_1: After iodine is added to both beakers, the starch suspension does not turn blue-black at all (it stays cloudy white or shows some unrelated tint), and the cellulose fibers show no distinctive response either; both beakers end up looking essentially the same color, giving no visual evidence that iodine reacts differently with starch than with cellulose.
level_2: The starch suspension develops the wrong color after iodine contact (for example, a plain brown or amber tint rather than blue-black), or the cellulose fibers unexpectedly turn blue-black, or both beakers change to the same blue-black shade; or a color change appears in a beaker before the iodine has actually reached the suspension or fibers.
level_3: The starch suspension does turn blue-black where the iodine touches it, and the cellulose fibers keep their original light color with no blue-black tint, but the color change in the starch beaker is patchy or streaky, covering only part of the suspension rather than spreading through it, or it takes a noticeably slow, hesitant onset rather than reading as a clear reaction.
level_4: The starch suspension turns a uniform blue-black essentially as soon as the iodine mixes in, filling the visible liquid rather than staying patchy; the cellulose fibers show no blue-black coloration anywhere and keep their original light, off-white tone; the blue-black response stays confined to the starch beaker, with no coloring bleeding into or appearing in the cellulose beaker.
level_5: All 4-point conditions are met, and in addition: the blue-black color in the starch beaker is dense and even across the whole suspension with no fading, streaking, or patchiness once it develops; the cellulose fibers keep their dry, matte, fiber-like look with no gloss, sheen, or discoloration suggesting an unintended reaction; the iodine solution shows its characteristic amber/brown color right up until it touches either beaker; no iodine pooling or dribble near the cellulose beaker creates a false impression that a reaction is starting there.

Spatiotemporal Consistency rubric:
level_1: A beaker instantly relocates to a different part of the frame with no continuous movement showing how it got there; the starch suspension or cellulose fibers pop into view or drop out of view with no pouring or removal action to explain the change; the whole scene suddenly flips from normal lighting to near-total darkness or back between consecutive frames; a beaker's shape abruptly bulges, cracks, or resizes with no visible cause.
level_2: Both beakers stay in the shot but behave impossibly: iodine appears already mixed into a beaker that was empty a moment before, with no visible pour shown; cellulose fibers drift upward or sideways as if floating, disconnected from any liquid or hand motion; the starch suspension churns or foams strongly with no stirring or pouring to cause it; the light hitting the beakers flickers, and the shadows they cast swing to a new angle with no camera or object movement to explain it.
level_3: The beakers, starch suspension, and cellulose fibers stay recognizable and continuous overall, but one small flaw is visible (for instance, the iodine stream seems to skip a beat as it's poured, making a droplet appear to jump position briefly, or a beaker's edge wavers slightly between frames, or the fibers blur briefly during a fast camera move), but nothing floats, relocates, or reverses its physical state.
level_4: Both beakers hold their position, size, and shape without shifting or rotating; the iodine stream descends and enters each beaker along a smooth, unbroken path with no skips; the starch suspension and cellulose fibers keep their relative places and their identifying look (cloudy liquid vs. solid fibers) throughout; the shadows the beakers cast keep falling the same way and at the same strength for the whole clip (they don't swing to a new angle or suddenly darken or lighten), and the beaker outlines never show tearing or doubling between frames.
level_5: All 4-point conditions are met, and in addition: the iodine droplets, beaker rims, and fiber edges stay sharp with no distracting blur during the key moments of addition; the beakers, suspension, and fibers read as one continuous, unbroken scene from the first frame to the last with no visible seams, jumps, or mismatched outlines; the camera viewpoint never drifts, tilts, or changes perspective; the iodine's fall into each beaker plays out at a steady, natural speed with no visible stutter, freeze, or sudden speed change.