Domain: Natural Science — Chemistry
Target concept: Silver mirror reaction of acetaldehyde

Video generation prompt: Add Tollens' reagent to a clean test tube, then add a few drops of acetaldehyde solution, and heat the mixture in a water bath at 50°C.

Evaluation guide:
(i) Target concept: Visual confirmation of aldehyde identity via reduction-driven metallic silver deposition on glass.
Minimum mechanism: Clean glass surface + alkaline diamminesilver(I) complex + reducing aldehyde + mild thermal activation → nucleation and lateral growth of contiguous Ag⁰ crystallites forming specular-reflective film.
(ii)Storyline: Frame opens on static overhead/slightly angled benchtop view showing three labeled items side-by-side: Tollens’ reagent bottle (left), acetaldehyde vial (center), clean test tube (right), and water bath (bottom). Step 1: Dropper extracts reagent from bottle and delivers stream into tube; liquid fills lower third. Step 2: Same dropper extracts acetaldehyde and delivers 2–3 discrete drops into tube; drops merge visibly with existing liquid. Step 3: Hand places tube upright into water bath (lower 1/3 submerged) and holds still. After ~2–3 seconds of stillness, silver deposit emerges progressively upward along inner wall, beginning near meniscus and expanding as a smooth, contiguous, mirror-bright band. Entire sequence occurs in fixed viewpoint with no camera motion, no object occlusion, and consistent lighting, all critical for verifying causality and spatial fidelity.

Manual:
Experimental Procedure
1. Place a clean, dry test tube upright on bench.
2. Add Tollens’ reagent (colorless alkaline [Ag(NH₃)₂]⁺ solution) using a dropper until ~1/3 full.
3. Add 2–3 drops of colorless acetaldehyde solution to the same tube.
4. Place tube upright into a water bath maintained at ~50°C and hold for ~30–60 sec.
Observation of Experimental Phenomena
A bright, reflective, silver-gray metallic mirror forms selectively on the inner wall of the test tube above the solution level; the bulk solution remains colorless and clear.
Summary of Experimental Principles
Acetaldehyde reduces [Ag(NH₃)₂]⁺ to metallic silver, which deposits as a coherent mirror on the clean glass surface; this is the defining positive test for aldehydes — the silver mirror reaction.

Prompt Grounding rubric:
level_1: No test tube, no Tollens' reagent bottle, no acetaldehyde vial, no dropper, and no water bath appear anywhere in the shot; none of the three actions (adding Tollens' reagent, adding acetaldehyde, heating in a water bath) is shown in any form.
level_2: A container or two is visible, but nothing marks any bottle as Tollens' reagent, no dropper or pipette appears, no small vial reads as the acetaldehyde solution, and no water bath is shown; at most a hand holds a tube with no clear reagent, addition, or heating action attached to it.
level_3: A clean test tube, a bottle consistent with Tollens' reagent (colorless, alkaline-looking liquid), a small vial of colorless acetaldehyde solution, a dropper, and a water bath are all visible; the three actions happen in order (reagent added to the tube, then acetaldehyde added, then the tube placed into the water bath), though the timing between steps or the tube's continuity in frame may be rough.
level_4: Everything in score 3 holds, and additionally: the test tube is transparent and upright throughout, the reagent bottle and acetaldehyde vial keep their distinct identities (no swapping the acetaldehyde vial for anything discolored, like vinegar), the dropper visibly delivers liquid into the tube rather than just hovering near it, the water bath shows warmed water (a faint shimmer or gentle convection is enough), and the tube's orientation and location stay the same across all three steps; it is never absent from frame for a shot and then back in a different spot.
level_5: Everything in score 4 holds, and additionally: the dropper tip touches the tube's inner wall or the liquid surface during each delivery rather than dispensing from mid-air, both liquid additions arrive as an unbroken stream or a small countable number of drops rather than an erratic spray, the tube sits with roughly its lower third submerged in the water bath and stays there without slipping, and no unrelated prop (gloves, extra bottles, a label reading a different chemical) enters the frame at any point.

Scientific and Causal Correctness rubric:
level_1: The tube's contents stay uniformly colorless and clear from the reagent addition through the full heating period: no gray or metallic sheen forms on the glass anywhere, and there is no visible link between adding the reagents, warming the tube, and any change in appearance.
level_2: Some visible change occurs (for instance the liquid clouds, bubbles vaguely, or shimmers), but it is not confined to the tube's inner wall, does not follow the addition-then-heating sequence, and never takes on the gray, reflective look of deposited silver.
level_3: After both liquids are added and the tube is warmed, a gray, reflective patch or band forms on part of the tube's inner wall; it does not yet cover the whole wetted height evenly, but it clearly appears only once heating has begun, and no black precipitate or brown discoloration competes with it for attention.
level_4: The gray-silver deposit forms only on the inner wall above the bulk liquid, not on the tube's bottom and not merely at the meniscus line; its edge is smooth and continuous rather than speckled or patchy, it appears only after warming starts, and the solution below it stays colorless and clear with no black or brown precipitate and no bubbling.
level_5: Everything in score 4 holds, and additionally the deposited layer shows a genuine mirror-like sheen (a bright highlight is visible on it under the scene's own lighting), its upper edge roughly tracks the water-bath fill line rather than climbing far above it, the surface reads as smooth and glossy rather than grainy or dull, and the solution beneath it stays clear and still, without visible currents disturbing the deposit's edge.

Spatiotemporal Consistency rubric:
level_1: The test tube jumps from one location or angle to another between shots with no motion connecting them; the liquid inside disappears in one frame and is back in the next; the room goes from lit to dark within a single frame with no fade; or the tube spins past a quarter turn with no visible rotation.
level_2: The tube shifts sideways or up/down by more than its own diameter between one addition and the next with nothing shown moving it; the dropper reappears in a different hand or angle with no path shown getting there; the water bath's surface height changes suddenly between shots; or the color and warmth of the light on the scene changes noticeably from one step to the next without explanation.
level_3: A brief cut hides the tube for a moment during one of the additions, the handheld framing wavers slightly, or the water's surface texture appears or settles without a clear cause, but the tube itself stays upright and in the same place in the scene across the reagent addition, the acetaldehyde addition, and the water-bath step, with no jump to a different location and no sudden warping of the tube or bottles.
level_4: Everything in score 3 holds, and additionally: the test tube, reagent bottle, acetaldehyde vial, and dropper each keep the same position relative to one another across the whole sequence; the water bath stays put at the bottom of the frame; the dropper's move from bottle or vial to tube is shown as one continuous motion rather than a jump cut; and the bright reflective highlight on the reagent bottle's glass and on the test tube's glass each stay in about the same spot on their respective surfaces as the dropper travels between them, rather than jumping to a different side.
level_5: Everything in score 4 holds, and additionally: the test tube's tilt away from vertical stays about the same the whole time, the dropper travels from bottle or vial to tube along one smooth path without doubling back, the water bath's surface shows a gentle, even shimmer rather than splashing or standing waves, and no ghosting trail, blocky smearing, or flicker appears on the tube, the liquid, or the forming mirror at any point.