Domain: Engineering — Food and Bioprocess Engineering
Target concept: Starch Gelatinization Degree Determination (Iodometric Method)

Video generation prompt: Take two test tubes, add the ungelatinized starch suspension to tube A, and the gelatinized starch solution to tube B. Add one drop of iodine solution to each test tube.

Evaluation guide:
(i) Target concept: Iodine staining differentiates starch granule integrity via amylose accessibility.
Minimum mechanism: In the ungelatinized suspension, amylose remains packed inside intact, semicrystalline starch granules and is largely inaccessible to iodine, so little or no blue-black complex forms; gelatinization swells and disrupts the granule structure, releasing amylose into solution where it readily forms the iodine-inclusion complex; iodine must be an aqueous I₂/KI solution that shows a brown baseline color when no accessible amylose is present.
(ii)Storyline: Frame opens on a static, front-facing view of two test tubes placed together, containing visibly distinct liquids (A: opaque white suspension; B: clear/amber solution). First, a pipette enters frame and delivers one iodine droplet to the center of tube A's liquid surface → dispersion occurs but the color stays dull brown/tan with no blue-black development, since the raw granules resist iodine penetration. Then, the same pipette delivers one iodine droplet to the center of tube B's liquid surface → immediate radial dispersion and onset of uniform blue-black color, since the released amylose readily binds iodine. The sequence is continuous, fixed-view, with no cuts or occlusion, and ends with the two contrasting final states held on screen for at least a second.

Manual:
Experimental Procedure
1. Place two test tubes together: tube A contains ungelatinized starch suspension, tube B contains gelatinized starch solution.
2. Add one drop of iodine solution to tube A, then one drop to tube B.
Observation of Experimental Phenomena
Tube A stays a dull brown/tan color — no blue-black develops; tube B turns dark blue-black.
Summary of Experimental Principles
In tube A, amylose remains locked inside intact, semicrystalline starch granules and is largely inaccessible to iodine, so little or no blue-black complex forms. Gelatinization in tube B swells and disrupts the granule structure, releasing amylose into solution where it readily forms the iodine-inclusion complex, producing the characteristic blue-black color.

Prompt Grounding rubric:
level_1: No test tubes are shown, or no starch suspension/solution is visible in either tube, or iodine solution is never added to either tube, or the two tubes are never shown together in the same shot.
level_2: Two containers appear but are not test-tube shaped (e.g., beakers or cups), or the liquids in the two containers look identical to each other before iodine is added, or iodine is added to only one of the two tubes, or the tubes are stacked/overlapping rather than placed for comparison.
level_3: Two cylindrical glass test tubes are shown together in frame; tube A holds an opaque, white, suspension-like liquid and tube B holds a clear, amber-tinted solution, visibly different from each other before any iodine is added; one drop of iodine is delivered to each tube in turn (A first, then B), with a droplet impact visible in both cases, but no resulting color change is shown yet.
level_4: All elements from score 3 are present AND the two tubes are matched in size and held upright at the same height, the iodine droplet is clearly seen leaving the pipette and landing near the center of each liquid surface, the addition to tube A completes before the pipette moves to tube B, and no other object blocks the view of either tube during the additions.
level_5: All elements from score 4 are present AND the tubes are legibly labeled “A” and “B” before the iodine is added, the labels stay visible and unobstructed throughout, the camera holds a single continuous framing with no cuts or re-zooms from before the first droplet to after the second droplet lands, and both final liquid states are held on screen together for at least a second so the two tubes can be compared directly.

Scientific and Causal Correctness rubric:
level_1: Neither tube changes color after its iodine drop, or both tubes turn the same color as each other (e.g., both blue-black or both staying brown), or a color change appears in a tube before its iodine drop actually lands.
level_2: A color change happens in only one tube, but the assignment is reversed from the underlying chemistry: the ungelatinized suspension in tube A turns deep blue-black while the gelatinized solution in tube B shows no blue-black; or both tubes show the same wrong hue (e.g., both purple or both orange) instead of the expected contrast.
level_3: After its iodine drop, tube B (the gelatinized starch solution) develops a visible blue-black color because its dissolved, iodine-accessible amylose forms the iodine-inclusion complex, while tube A (the ungelatinized starch suspension) stays a dull brown/tan color because its amylose remains locked inside intact, iodine-resistant starch granules; this contrast is visible for at least a second after both drops have landed.
level_4: All elements from score 3 are present AND the blue-black color in tube B spreads to fill the liquid fairly evenly rather than staying as an isolated streak or floating patch, and tube A shows no patches, rings, or specks of blue-black anywhere in its volume; the two tubes' colors stay clearly different from each other rather than drifting toward a similar shade.
level_5: All elements from score 4 are present AND the blue-black in tube B looks like the classic dark indigo-to-black iodine–starch complex (not greenish or purplish), the brown/tan in tube A stays translucent rather than turning cloudy or milky, and no lighting glare, reflection, or color bleed between the two tubes makes either result ambiguous to a viewer comparing them side by side.

Spatiotemporal Consistency rubric:
level_1: One of the test tubes vanishes from the frame and reappears later, or the two tubes swap positions between shots, or the liquid level in a tube jumps up or down with no droplet or pouring motion to explain it, or the iodine droplet appears already spread through the liquid before it touches the surface, or the lighting abruptly flashes, flickers, or shifts between the iodine addition to tube A and the addition to tube B with no visible cause.
level_2: The two tubes drift apart or move relative to each other during the shot (e.g., the camera pushes in on one while the other shrinks in the frame), or the camera angle changes noticeably partway through, or a liquid surface ripples or shifts on its own between frames with no droplet or contact causing it, or the pipette's droplet appears to pause in mid-air before contacting the liquid.
level_3: Both tubes stay in the same place and orientation through the whole shot; the camera doesn't cut or jump; each liquid surface is calm before its iodine drop and shows a brief, natural ripple right when the drop lands; the droplet's fall from the pipette tip to the surface looks continuous rather than skipping partway.
level_4: All elements from score 3 are present AND the droplet falls in a straight, consistent path into each tube, the ripple it creates spreads outward evenly in both tubes, both tubes stay equally sharp and in focus throughout (no one tube suddenly blurring while the other stays crisp), and there's no visible stutter or repeated frame anywhere in the sequence.
level_5: All elements from score 4 are present AND the liquid's meniscus in each tube looks steady and consistent both before and after its droplet lands, the visible ripple in each tube begins at the moment its droplet actually touches the surface rather than slightly before or after, the droplet and resulting color change stay clear enough to follow with the eye rather than smearing into a blur, and the liquid's motion in both tubes looks like ordinary fluid settling under gravity rather than anything artificial.