Domain: Healthcare — Pharmaceutical Chemistry
Target concept: Chloramphenicol Detection

Video generation prompt: An appropriate amount of chloramphenicol sample was placed in a test tube, followed by the addition of ethanol and silver nitrate solution. The reaction of the solution inside the test tube was observed.

Evaluation guide:
(i) Target concept: Qualitative screening reaction in which silver nitrate reacts with free chloride ion associated with a chloramphenicol sample to form a white, insoluble silver chloride precipitate. Chloramphenicol's two chlorine atoms are covalently bound within its dichloroacetamide side chain and are not freed as chloride ions merely by dissolving the drug in ethanol at room temperature; any precipitate seen in this simple ethanol/silver-nitrate procedure therefore reflects free chloride already present as a trace impurity, or slowly released as the drug degrades in solution; this is a preliminary/supportive halide test, not a structure-specific confirmatory identification of chloramphenicol.
Minimum mechanism: Chloramphenicol sample is dissolved in ethanol; silver nitrate solution is added after dissolution; if free chloride is present or released, it reacts with the silver ion to form a white, insoluble precipitate confined to the test tube interior.
(ii)Storyline: [Phase 1] Static wide shot showing labeled reagent containers and empty test tube. [Phase 2] Hand places white crystalline solid into tube: visible contact and static rest. [Phase 3] Ethanol poured into tube: liquid enters, wets solid, meniscus rises. [Phase 4] Silver nitrate solution poured: contact point visible, localized turbidity appears. [Phase 5] White precipitate settles or stays suspended and persists for at least 1 second with no dissolution or dispersion. All phases occur in fixed frontal viewpoint; no camera movement; no occlusion of the test tube interior during addition or observation.

Manual:
Experimental Procedure
1. Place a small amount of white crystalline chloramphenicol into a clean test tube.
2. Add ethanol to dissolve the sample.
3. Add silver nitrate solution dropwise.
4. Observe formation of a white precipitate.
Observation of Experimental Phenomena
A white precipitate forms upon addition of silver nitrate solution to the ethanol-dissolved chloramphenicol sample; no color change appears in the supernatant; the precipitate remains stable and does not redissolve.
Summary of Experimental Principles
Chloramphenicol's two chlorine atoms are covalently bound within its dichloroacetamide side chain and are not released as free chloride ions by simple dissolution in ethanol at room temperature. Under alkaline conditions, chloramphenicol's nitro group can separately reduce silver ion to elemental silver, but that side reaction is not expected here since no alkali is used. The white precipitate observed in this test is therefore attributed to free chloride already present as a trace impurity in the sample, or released by slow degradation of chloramphenicol in ethanol — making this a preliminary, supportive halide-screening reaction rather than a definitive structural confirmation of chloramphenicol itself.

Prompt Grounding rubric:
level_1: No test tube is shown; the white crystalline chloramphenicol sample never appears; neither the ethanol nor the silver nitrate solution is shown; nothing is added to the test tube; no part of the addition-and-reaction sequence is depicted.
level_2: A test tube holding a white solid appears, but the solid is never actually placed into the tube on screen; the ethanol and silver nitrate containers are missing or mislabeled (e.g., labeled as water or saline); no pouring action into the tube is shown; no reaction sequence follows.
level_3: A clear test tube is visible; a small amount of white crystalline solid identified as chloramphenicol is shown being placed into the tube; separate, correctly labeled containers of ethanol and silver nitrate solution are both visible; at least one of the two reagents is poured into the tube; the moment right after both reagents have combined is not shown.
level_4: All items are present and correctly labeled (test tube, white crystalline chloramphenicol, colorless ethanol, colorless silver nitrate solution), and the sequence is correct: chloramphenicol goes into the tube first, ethanol is poured in second, silver nitrate solution is poured in third, with visible contact between each reagent and the tube's contents; the moments after the final addition are not shown.
level_5: Meets all 4-point criteria, and after silver nitrate is poured in, the camera holds on the test tube for at least one more second within the same continuous shot, so the resulting mixture is visible before the clip ends; nothing is swapped, mislabeled, skipped, or added out of order.

Scientific and Causal Correctness rubric:
level_1: The solution inside the tube stays clear and colorless the whole time, with no precipitate or cloudiness ever appearing, or any turbidity that does appear has no connection to when silver nitrate is added.
level_2: The liquid changes color (e.g., turns yellow or brown) but no solid precipitate ever forms; or a precipitate forms but is the wrong color (e.g., blue, green, or black); or cloudiness appears before silver nitrate touches the tube's contents; or cloudiness appears right after ethanol is added, before any silver nitrate has been introduced.
level_3: A white precipitate appears only after the silver nitrate solution is added (not before, and not from the ethanol alone), stays inside the test tube, does not dissolve or vanish again before the clip ends, and its color reads as white rather than off-white, cream, or gray.
level_4: Meets all 3-point criteria, and the precipitate spreads through the liquid starting from the point where the silver nitrate stream enters, and settles or stays suspended fairly evenly rather than clumping into a few large chunks or floating as an oily film, while the liquid around the precipitate stays clear and colorless.
level_5: Meets all 4-point criteria, and the precipitate appears within roughly a second of the silver nitrate contacting the ethanol/chloramphenicol mixture, consists of fine particles spread evenly through the tube's contents, shows no accompanying color change in the surrounding liquid, and once formed does not redissolve, clear up, or separate into layers before the clip ends.

Spatiotemporal Consistency rubric:
level_1: The test tube vanishes from view and then reappears later in the clip; the chloramphenicol solid jumps directly from the hand into the tube with no visible path of motion; the ethanol or silver nitrate stream seems to teleport into the tube rather than pour in; a precipitate is visible in the tube before either reagent has touched its contents; the room lighting suddenly changes between one frame and the next; the tube tilts more than about 45 degrees with nothing shown holding or supporting it.
level_2: The test tube stays in view but suddenly shifts to a different spot in the frame between shots; a reagent container disappears mid-pour; the precipitate blinks in and out of view across frames instead of staying put once it appears; the shadow cast by the tube or a container swaps to the opposite side with no change in the light source; the tube's glass appears to bend or deform.
level_3: The test tube stays in the same place and at the same angle throughout; every object keeps the same size and the same position relative to the others; each pour follows one continuous, unbroken path into the tube; once the precipitate appears it stays put and keeps building up rather than jumping around; the lighting stays steady with no sudden flashes; the tube's glass stays rigid with no bending or transparency glitches.
level_4: Meets all 3-point criteria, and each pour flows smoothly from container to tube with a natural slowing at the end rather than an abrupt stop; the precipitate builds up gradually rather than appearing to snap into existence between two frames; the overall brightness and light direction on the tube and containers stay the same from the first frame to the last; nothing in the shot jitters, stretches, or morphs between frames.
level_5: Meets all 4-point criteria, and the test tube's position, angle, and size never vary across the whole clip; the background and container edges don't shift relative to each other as if the camera moved; every action (placing the solid, pouring the ethanol, pouring the silver nitrate) reads as one smooth, physically plausible motion with no abrupt starts or stops; the precipitate's growth is continuous and confined to the tube with no part of it jumping, splitting apart, or duplicating; the direction and softness of shadows on the tube and containers stay the same throughout.