Domain: Healthcare — Clinical Laboratory Science
Target concept: Hemoglobin Determination (Colorimetric Method)

Video generation prompt: Take 20 μL of anticoagulated blood and add 5 mL of hemoglobin reagent. Mix thoroughly and let stand for 2 minutes. Place the tube in the spectrophotometer, set the wavelength to 540 nm, and observe the spectrophotometer reading and changes in solution color.

Evaluation guide:
(i) Target concept: Colorimetric quantification of hemoglobin via cyanmethemoglobin formation.
Minimum mechanism: Anticoagulated blood must contain intact hemoglobin; reagent must contain potassium ferricyanide and potassium cyanide; mixing enables oxidation and complexation; standing allows reaction completion; 540 nm is the sole wavelength where cyanmethemoglobin has peak absorbance; absorbance requires a homogeneous colored solution in a light-path-compatible cuvette.
(ii)Storyline: [Phase 1: Preparation] Blood tube and reagent vial are side-by-side in fixed lab bench view; pipette approaches blood surface → contacts → aspirates → retracts. [Phase 2: Reaction Initiation] Pipette moves to reagent vial → dispenses → vial is inverted twice → returned upright. [Phase 3: Reaction Completion] Vial remains motionless for full standing duration → uniform color emerges across liquid column. [Phase 4: Measurement] Mixture is poured into cuvette → cuvette carried to spectrophotometer → inserted fully → display activates and stabilizes. All phases occur in fixed viewpoint with no camera movement; critical actions (contact, inversion, stillness, insertion) are fully visible and unoccluded; color development and reading appearance are temporally locked to their causal predecessors.

Manual:
Experimental Procedure
1. Draw 20 μL anticoagulated blood using calibrated pipette.
2. Dispense into 5 mL hemoglobin reagent vial.
3. Mix thoroughly by inverting tube 2×.
4. Let stand undisturbed for 2 minutes.
5. Transfer mixture to cuvette and place in spectrophotometer at 540 nm.
Observation of Experimental Phenomena
- Solution changes from colorless/pale yellow to a uniform cherry-red/pink hue after standing, consistent with cyanmethemoglobin formation.
- Spectrophotometer displays a stable positive numeric absorbance reading only after cuvette insertion.
Summary of Experimental Principles
- Hemoglobin reacts with cyanide and ferricyanide in the reagent to form cyanmethemoglobin, which absorbs maximally at 540 nm; absorbance is proportional to hemoglobin concentration.

Prompt Grounding rubric:
level_1: No anticoagulated blood sample, hemoglobin reagent, or spectrophotometer is visible; none of the required objects (a small-volume pipette, blood tube, reagent vial, cuvette, spectrophotometer) appear; there is no mixing action, no standing period, no wavelength setting, and no reading observation.
level_2: At least one correct object appears (e.g., a tube or pipette), but there is no identifiable transfer of a small blood volume, no reagent addition, no mixing motion, and no spectrophotometer interface or cuvette placement; the sequence is absent or fully scrambled.
level_3: All core objects are present: anticoagulated blood in a small tube, a micropipette sized for microliter volumes, a hemoglobin reagent vial, a mixing tube (or cuvette), and a spectrophotometer with a visible display; the sequence shows blood transfer → reagent addition → mixing → standing → instrument placement → reading observation, but at least one step is misordered or lacks a clear causal link (e.g., mixing shown after the tube is already placed in the spectrophotometer).
level_4: All core objects are correctly identified by type and relative scale (the pipette clearly smaller than the reagent vial; the blood tube visually distinct from the reagent vial; the spectrophotometer display showing a numeric readout); the sequence is fully correct (blood drawn, added to reagent, mixed, left standing, loaded into the instrument, and read), with no missing step and no extraneous action, but one non-core flaw remains (e.g., the pipette tip's contact with the blood surface is not clearly visible, the display is hard to read due to glare, or the cuvette looks not fully seated).
level_5: All core objects are unambiguous in type and relative scale: a small-volume pipette clearly smaller than the reagent vial, a blood tube holding dark red liquid consistent with anticoagulated whole blood, a reagent vial holding a colorless or pale-yellow liquid, a mixing tube holding the combined solution, a transparent filled cuvette, and a spectrophotometer with an active display showing a numeric value; every action is visually complete and causally connected: the pipette tip contacts the blood, withdraws, moves to the reagent tube, dispenses, the tube is inverted at least twice, held still for a visible duration, transferred to the cuvette, inserted into the spectrophotometer, and the display updates with a stable reading, with no ambiguity, occlusion, or jump in the sequence.

Scientific and Causal Correctness rubric:
level_1: No color change occurs; solution remains colorless or unchanged throughout; no reading appears on the spectrophotometer; blood and reagent remain physically separated; there is no causal link between mixing and any color development or reading.
level_2: A color appears, but it is incorrect (e.g., blue, green, purple, or black) and inconsistent with cyanmethemoglobin formation; a reading appears but is unrelated to the color (e.g., displayed before mixing or before standing); there is no observable relationship between mixing and color onset.
level_3: Solution develops a uniform cherry-red to pink hue after mixing and standing (matching the expected cyanmethemoglobin endpoint), and the spectrophotometer displays a numeric reading; however, either the color appears before standing, or the reading appears before cuvette insertion, or the color is patchy/non-uniform, or the reading is displayed without a visible cuvette present.
level_4: Cherry-red to pink color develops uniformly only after mixing and standing (no color before standing, color fully developed by the end of standing); spectrophotometer reading appears only after the cuvette is fully inserted and stable; color and reading occur in the correct causal order: mixing → standing → color emergence → cuvette loading → reading appearance; no incorrect intermediate colors (e.g., purple, brown, gray) and no premature or missing phenomena.
level_5: Color transition is clean and correctly timed: the solution is colorless or pale yellow before mixing; immediately after mixing there is no color change yet; only after the full standing period (shown by uninterrupted stillness) does a uniform cherry-red to pink color emerge across the entire solution volume with no streaks, gradients, or phase separation; the spectrophotometer reading appears only once the cuvette is fully seated, stays stable during observation, and shows a non-zero positive absorbance value; every causal link is visually intact: no color without standing, no reading without color, no reading without cuvette insertion.

Spatiotemporal Consistency rubric:
level_1: The pipette jumps directly from the blood tube to the spectrophotometer with no travel shown in between; the cuvette appears already inside the spectrophotometer with no insertion motion; the blood sample vanishes and reappears in the tube; the lighting in the lab bench scene changes abruptly from one frame to the next; or the test tube's shape distorts unnaturally.
level_2: The pipette tip appears to pass through the tube wall rather than staying within its opening; the mixing motion is not continuous (e.g., the inversion starts mid-air or skips part of the rotation); the standing period shows the tube flickering or blinking in and out; the spectrophotometer's display changes value while no cuvette is present in the slot; or the shadow cast by the tube or pipette swaps to the opposite side between frames with no light source moving.
level_3: All actions (aspiration, dispensing, mixing, standing, and insertion) show continuous motion with no teleportation or breakage of the tube, pipette, or cuvette; every object keeps a consistent size, shape, and position relative to the bench; the shadow cast under the tube and reagent vial keeps the same direction and depth of darkness throughout; there are no abrupt cuts or dropped frames; one minor slip is allowed, such as the pipette tip briefly passing behind the experimenter's hand during transfer, or a slight tilt of the cuvette beyond what a steady hand would produce.
level_4: All motions are smooth and physically plausible: the pipette approaches the blood surface, contacts it, withdraws, moves steadily to the reagent vial, and dispenses with a visible meniscus change; mixing shows a full inversion of the tube without spilling; the standing tube shows no vibration or flow; the cuvette slides into the spectrophotometer slot without misalignment or bouncing; the shadow and lighting stay consistent with the earlier frames; one small imperfection is allowed, such as a brief reflection glint on the cuvette or a slight wobble of the spectrophotometer housing as the cuvette is inserted.
level_5: Every step is fully traceable with no spatiotemporal break: the pipette's path from rest to contact, withdrawal, transit, and dispensing is continuous; the tube is inverted a visible two full times with the liquid staying contained; the tube sits absolutely still for the entire standing period (no ripple, meniscus drift, or vibration); the cuvette slides straight into the spectrophotometer slot and stops cleanly; the display only updates after the cuvette is seated; every object keeps the same spatial relationship to the bench and to each other, the lighting geometry stays the same throughout, and glass, liquid, and plastic surfaces behave the way real materials do (refraction in the glass tube, a curved meniscus in the liquid) across all frames.