Domain: Engineering — Food and Bioprocess Engineering
Target concept: Flavonoid Determination (Aluminum Salt Colorimetric Method)

Video generation prompt: Take 2 mL of Sophora japonica extract in a test tube, add 2 drops of aluminum nitrate solution, shake thoroughly, then add 1 drop of sodium hydroxide solution.

Evaluation guide:
(i) Target concept: Aluminum ion-mediated flavonoid chelation under controlled alkalization produces a stoichiometric, bathochromically shifted chromophore. Minimum mechanism: Flavonoid must be present in extract; Al³⁺ must bind prior to OH⁻ introduction; alkaline pH must trigger deprotonation and complex stabilization: no color change without both reagents in sequence.
(ii)Storyline: [Frame 0–1] Static shot: upright test tube containing pale yellow liquid (Sophora extract). [Frame 2–3] Aluminum nitrate dropper enters view from right, releases two distinct droplets into tube; liquid remains pale yellow. [Frame 4–5] Hand grips tube and executes rapid vertical oscillation (shaking); liquid agitates uniformly, no spillage, no color shift. [Frame 6–7] Sodium hydroxide dropper enters from same side, releases one droplet; liquid surface briefly ripples, then settles. [Frame 8–10] Color transforms uniformly across entire liquid volume to orange-brown and holds; no fade, no gradient, no particulates. Perspective: Fixed frontal close-up; entire tube and dropper tips always fully visible; no occlusion of liquid column at any frame.

Manual:
Experimental Procedure
1. Place 2 mL Sophora japonica extract into a clean test tube.
2. Add exactly 2 drops of aluminum nitrate solution using a calibrated dropper.
3. Cap and shake tube thoroughly for ~1 second.
4. Add exactly 1 drop of sodium hydroxide solution.
Observation of Experimental Phenomena
- Initial extract: pale yellow or light amber liquid.
- After Al(NO3)3 + shaking: no color change; remains pale yellow/amber.
- After NaOH addition: immediate, uniform transition to stable orange-brown color.
Summary of Experimental Principles
Flavonoids in Sophora japonica form a stable colored complex with aluminum ions under alkaline conditions; aluminum nitrate provides Al³⁺, NaOH raises pH to enable chelation and chromophore development.

Prompt Grounding rubric:
level_1: No test tube is shown, no pale-yellow Sophora japonica extract appears, and neither the aluminum nitrate nor the sodium hydroxide droppers/bottles are shown; none of the three required actions (adding aluminum nitrate, shaking, adding sodium hydroxide) takes place.
level_2: A test tube, or the extract liquid, or a single dropper appears, but the two reagents are not both present and distinguishable (e.g., only one dropper is shown, or the aluminum nitrate and sodium hydroxide droppers look identical and unlabeled); fewer than two of the three required actions occur; the shaking motion is missing, applied to an empty tube, or applied at the wrong point in the sequence.
level_3: A test tube holding pale-yellow Sophora japonica extract is visible; two distinguishable droppers or bottles for aluminum nitrate and sodium hydroxide are shown; the sequence proceeds as 2 droplets of aluminum nitrate entering the tube followed by vigorous shaking, then exactly 1 droplet of sodium hydroxide entering the tube, in this order, with no step skipped or reordered.
level_4: Everything described for a score of 3 is present, and in addition each dropper tip sits directly over the tube's opening while releasing its droplets, with no droplets missing the tube; the shaking happens only after the aluminum nitrate addition and before the sodium hydroxide addition; no unrelated actions (such as wiping the tube, writing a label, or pouring from another flask) interrupt the three core steps.
level_5: Everything described for a score of 4 is present, and in addition both droppers keep the same shape, labeling, and relative size every time they reappear; the hand shaking the tube keeps its grip on the tube itself without the arm sweeping outside the frame; the liquid surface stays fully visible during every addition, with no splashing, overflow, or momentary blocking of the tube; the three steps play out as one continuous sequence with no repeated or skipped frame between them.

Scientific and Causal Correctness rubric:
level_1: The Sophora japonica extract keeps its original pale-yellow tint straight through the final sodium hydroxide addition and beyond, or it shifts to a hue inconsistent with the aluminum–flavonoid chelation pathway (e.g., turning green, blue-black, or bleaching to colorless); alternatively, an orange-brown change appears before the sodium hydroxide drop is ever added, or a precipitate/turbid layer forms instead of a homogeneous color shift.
level_2: A color shift does occur, but at the wrong step: for instance the liquid turns orange-brown as soon as the aluminum nitrate is shaken in, before sodium hydroxide is ever added; or the tone that appears is implausible for this chelate (e.g., a deep purple or bright pink rather than orange-brown); or cloudiness/turbidity develops right after the aluminum nitrate step instead of the liquid staying clear until the hydroxide addition.
level_3: The extract stays visibly pale yellow through the aluminum nitrate addition and shaking, with no premature color change; within roughly one to two seconds of the sodium hydroxide droplet entering the liquid, the entire tube contents shift to an orange-brown color and hold that hue, with no reversal back toward yellow and no separation into layers.
level_4: Everything described for a score of 3 holds, and in addition the orange-brown color is even across the whole liquid column: no darker ring at the surface, no paler zone near the bottom, no floating clumps; no bubbling or fizzing accompanies either addition; the color change happens exactly once, tied only to the sodium hydroxide step, and does not flicker or repeat.
level_5: Everything described for a score of 4 holds, and in addition the orange-brown hue stays constant in tone from the moment it appears until the final frame: it neither drifts toward red nor brown-black nor washes out toward pale yellow; no oily film, floating solid, or settling sediment ever appears that would be inconsistent with a clean flavonoid–aluminum–hydroxide color reaction.

Spatiotemporal Consistency rubric:
level_1: The test tube's liquid fill line jumps up or down between frames with no dropper visibly adding or removing liquid; the tube itself appears in a different spot on the countertop between the aluminum nitrate and sodium hydroxide steps with no hand shown carrying it there; the two droppers swap appearance or color with one another between entrances even though each is meant to stay visually distinct; the room's light source visibly swaps from one type to another (e.g., bright daylight flooding in, then suddenly warm lamp light) partway through the sequence rather than staying the same throughout; the tube tips over or spins past vertical with no hand visibly turning it.
level_2: The test tube shifts position or tilt between the two additions without a hand visibly moving it; the aluminum nitrate or sodium hydroxide dropper releases a different number of droplets than the two and one specified for each step; the shaking motion starts or stops instantly with no visible ramp-up or slow-down; the liquid appears mid-splash in one frame and perfectly calm in the very next with no in-between motion.
level_3: The test tube stays in the same place and orientation across both additions, moving only in ways consistent with being held and gently shaken by a hand that stays in frame; each of the two droppers approaches and withdraws from the same side of the tube and keeps its own distinct look (shape, color, or label) every time it reappears, so aluminum nitrate and sodium hydroxide stay visually distinguishable from one another throughout; the tube's vertical axis and its contact point with the surface below stay put; the scene shows no abrupt cut or camera jump between the aluminum nitrate and sodium hydroxide steps; the liquid's fill line rises only in small steps that match each addition (two drops, then one), never jumping by a large amount within a single frame.
level_4: Everything described for a score of 3 holds, and in addition each droplet visibly leaves its dropper tip and falls into the liquid rather than appearing to float free of the tip beforehand; the shaking motion visibly speeds up to its peak and slows back to rest instead of snapping on or off; the liquid's meniscus visibly deforms while being shaken and settles back to flat within a beat after the shaking stops.
level_5: Everything described for a score of 4 holds, and in addition the test tube and both hands stay visually steady with no sudden drifting or repositioning between the aluminum nitrate and sodium hydroxide additions; each dropper fully withdraws from the frame or returns to a resting position after delivering its droplets before the next dropper enters, so no two droppers are ever visible overlapping at the tube's mouth at the same time; the liquid's fill line increases by an amount consistent with exactly two drops, then one final drop, with the total rise across the whole sequence matching that 2+1 addition pattern and no sudden unexplained jump in volume at any point.