Domain: Engineering — Food and Bioprocess Engineering
Target concept: Determination of Calcium in Food by the Ammonium Oxalate Colorimetric Method

Video generation prompt: Take 2 mL of milk extract into a test tube and add ammonium oxalate solution.

Evaluation guide:
(i) Target concept: Visual confirmation of the calcium-oxalate precipitation step that forms the front end of the ammonium oxalate method for determining calcium in food; this video depicts only that qualitative precipitate-formation stage, not the subsequent quantitative measurement (e.g., redissolution and titration, or a colorimetric finish) that the full method requires.
Minimum mechanism: Milk extract must contain soluble calcium; ammonium oxalate must be added to provide oxalate ions; reaction must occur in aqueous phase at room temperature to yield immediate, stoichiometric white precipitate.
(ii)Storyline: [Frame 0–2] Static shot: upright test tube with 2 mL milk extract (cloudy white, meniscus at calibration mark); [Frame 3–5] Distinct container (dropper/cylinder) enters frame from top-right; clear liquid dispenses in steady stream into tube; [Frame 6–8] Gentle swirling motion begins; [Frame 9–10] Uniform white precipitate appears throughout liquid column and remains suspended, with no color shift, no dissolution, no delay >2 s after mixing.

Manual:
Experimental Procedure
1. Place a clean test tube upright in holder.
2. Pipette 2 mL of milk extract into the test tube.
3. Add ammonium oxalate solution dropwise while gently swirling.
Observation of Experimental Phenomena
White precipitate forms immediately upon addition and remains suspended briefly before settling as a fine, dense layer.
Summary of Experimental Principles
Calcium ions in milk react with oxalate ions to form an insoluble white precipitate of calcium oxalate (CaC₂O₄). This precipitation is the sample-preparation stage of the broader ammonium oxalate method for determining calcium in food, in which the isolated precipitate is subsequently redissolved and quantified (for example, by permanganate titration or a follow-up colorimetric assay) — steps that occur after, and are not shown in, this video. What this video depicts is only the qualitative formation of the white precipitate, not the quantitative measurement step itself.

Prompt Grounding rubric:
level_1: The test tube itself is missing from the frame; there is no milky liquid inside it; the ammonium oxalate solution and whatever is used to dispense it (dropper or graduated cylinder) never appear; nothing shows a roughly 2 mL amount of milk extract; no pouring or dispensing action of any kind takes place.
level_2: A test tube holding some liquid is visible, but the liquid does not look like milk extract (it is not a light, opaque, milky-white liquid) or nothing marks it as such; the ammonium oxalate solution and its dispensing container are never shown; no action of adding a solution to the tube takes place.
level_3: A test tube holds a light, opaque, milky-white liquid consistent with milk extract; a separate container holding a clear, colorless liquid (the ammonium oxalate solution) is visible; that container is shown dispensing its liquid toward the test tube, but the dispensing begins before the test tube is fully shown in frame, or the stream is not clearly shown reaching the milk extract.
level_4: The test tube sits still and is fully in frame before dispensing starts; the milk extract's level roughly matches a 2 mL fill relative to the tube's markings or typical proportions; the ammonium oxalate container is clearly a separate object (e.g., a dropper bottle or graduated cylinder) from the test tube; once dispensing starts, a continuous stream of clear liquid enters the tube opening without spilling over the side or missing the tube.
level_5: Everything required for score 4 holds, AND the test tube carries its own calibration markings with the milk extract's meniscus sitting right at the 2 mL line; the ammonium oxalate container is labeled or looks like standard lab glassware (e.g., an amber dropper bottle marked '(NH₄)₂C₂O₄'); the dispensing stops once the liquid level has risen by roughly the amount a typical few-drop addition would add (about 0.5–1 mL above the starting level); no hand, tool, or other object blocks the view of the tube or the path of the incoming liquid at any point.

Scientific and Causal Correctness rubric:
level_1: No extra cloudiness or solid particles appear in the tube beyond the milk extract's own starting opacity; the liquid looks the same at the end of the video as it did before the ammonium oxalate solution was added; nothing resembling a precipitate ever forms.
level_2: Some visible change occurs after the addition, but it does not match a white precipitate forming, e.g., the liquid instead turns a different color (yellow, pink, etc.), or bubbles/foams instead of clouding, or a solid appears in the tube before the ammonium oxalate solution has been added at all.
level_3: The ammonium oxalate solution is added to the milk extract; a white, cloudy precipitate becomes visibly denser or coarser than the milk extract's own starting opacity; but the precipitate is patchy, only appears at the very bottom, or takes noticeably longer than a couple of seconds to show up after mixing.
level_4: Right after the ammonium oxalate solution is added, gentle swirling is shown; within about 3 seconds, fine white precipitate becomes visible spread through the whole liquid column, not just at the bottom, before it starts to settle; the liquid stays milky-white throughout with no yellow, brown, pink, or other tint appearing.
level_5: Everything required for score 4 holds, AND the precipitate stays plain white with no gray, yellow, or pink cast; the precipitate looks like fine, even particles rather than clumping into pieces a quarter of the tube's width or larger; the precipitate fills the whole visible liquid column right after mixing and stays suspended for at least about 2 seconds before any settling begins; once settling starts, it proceeds as a steady downward drift rather than the whole cloud suddenly dropping or splitting into a sharp layer within the first 5 seconds.

Spatiotemporal Consistency rubric:
level_1: The test tube is shown fully empty in one frame and then already holding the milky liquid in the very next frame with no pouring shown; the dropper or cylinder used to add the ammonium oxalate solution appears already empty and already retracted from frame before any stream of liquid is shown leaving it; the level of liquid inside the tube jumps up or down abruptly between two consecutive frames with no addition or removal action visible; or the room's lighting or overall brightness suddenly switches to a very different look between frames (e.g., a bright shot cutting to a dim one) with no visible cause.
level_2: The test tube's position on screen shifts sideways by roughly a third of its own width between the pouring shot and the swirling shot with no hand or holder movement shown to explain it; the stream of ammonium oxalate solution flowing into the tube blinks on and off rather than falling as one continuous stream; the white precipitate is shown fully settled at the bottom of the tube in one frame and then back to being spread evenly through the liquid in a later frame, with no shaking or swirling shown to cause the change.
level_3: The test tube stays in the same place and orientation on screen through the pouring step, and any tilt or rotation seen afterward is limited to the deliberate gentle swirling used to mix the reagent in, not an unexplained shift; once the ammonium oxalate solution begins flowing into the tube it keeps flowing without gaps until the addition is finished; the liquid level inside the tube rises steadily and only upward while liquid is being added, never dropping back down mid-addition; the tube and its liquid keep a consistent, solid appearance throughout (no part of the tube or liquid warps, splits, or flickers).
level_4: Everything required for score 3 holds, AND the camera's framing of the test tube does not pan, tilt, or zoom at any point in the video; the test tube keeps the same position and orientation from the pouring step up through the start of swirling, and any tilt during the gentle swirling itself reads as a smooth, hand-controlled motion rather than an abrupt, unexplained jump; the liquid's surface rises without pausing or reversing direction as the ammonium oxalate solution is added; the incoming stream keeps a steady width and path from the dropper or cylinder tip down to the liquid surface.
level_5: Everything required for score 4 holds, AND the incoming stream of ammonium oxalate solution narrows slightly as it falls, the way a real thin stream of liquid does, rather than staying a uniform cylinder; the liquid surface's rise slows naturally as the addition nears its end rather than stopping abruptly mid-motion; no frame is repeated or shown out of order, and the background behind the test tube does not shift relative to the tube as the shot proceeds.