Domain: Natural Science — Chemistry
Target concept: Preparation of Cinnamic Acid (Perkin Reaction)

Video generation prompt: A mixture of benzaldehyde and acetic anhydride was added to a three-necked flask, and anhydrous potassium acetate was introduced as a catalyst. The mixture was heated to reflux, and the flask was observed after cooling.

Evaluation guide:
(i) Target concept: Formation of potassium cinnamate via Perkin condensation, observed as a reflux mixture that darkens with heating.
Minimum mechanism: Catalyst (anhydrous potassium acetate) must be solid and added prior to heating; reflux must occur to drive the condensation between benzaldehyde and acetic anhydride; under these basic, anhydrous reflux conditions the product forms initially as potassium cinnamate (a carboxylate salt) that stays dissolved/suspended in the dark, viscous reaction mixture; simple cooling alone does not yield discrete crystalline cinnamic acid, since isolating the free acid requires a later aqueous hydrolysis and acidification step that is not part of this procedure.
(ii)Storyline: [Frame 0–1s] Empty three-necked flask centered, static view. [1–2s] Two colorless liquids poured sequentially into flask (distinct streams, no mixing shown yet). [2–3s] White crystalline solid dispensed into flask. [3–4s] Reflux condenser attached to center neck. [4–7s] Heating begins → condensate forms and moves continuously downward in condenser, and the pot liquid gradually darkens toward amber/brown. [7–8s] Heating stops; flame/glow extinguishes. [8–10s] Flask remains motionless; final frame shows a single dark, viscous liquid mixture that has thickened slightly on cooling: no discrete white crystalline layer forms; no agitation, no stirring, no viewpoint change.

Manual:
Experimental Procedure
1. Place empty three-necked flask on stand.
2. Add colorless benzaldehyde and colorless acetic anhydride into flask.
3. Add white crystalline anhydrous potassium acetate.
4. Attach reflux condenser vertically to center neck.
5. Heat flask to reflux (visible condensate moving down condenser; mixture gradually darkens toward amber/brown).
6. Stop heating; allow flask to cool undisturbed.
Observation of Experimental Phenomena
After cooling: the flask contains a single dark amber-to-brown, viscous liquid mixture — no discrete white crystalline solid forms at this stage, because the cinnamic acid product is present as dissolved potassium cinnamate salt; isolating free, crystalline cinnamic acid requires a subsequent hydrolysis (water addition) and acidification workup that is not part of this procedure.
Summary of Experimental Principles
Perkin reaction: benzaldehyde and acetic anhydride condense via an enolate (Perkin) mechanism, catalyzed by potassium acetate, to form potassium cinnamate directly within the basic reflux mixture; free crystalline cinnamic acid is obtained only after this crude mixture is later hydrolyzed with water and acidified.

Prompt Grounding rubric:
level_1: No three-necked flask appears anywhere; benzaldehyde, acetic anhydride, and anhydrous potassium acetate are never shown; there is no reflux setup and no heating; no cooling step is depicted.
level_2: At least one relevant object appears (a flask, a liquid, or a white solid), but the setup is wrong: the flask shown is not actually three-necked, one or more reagents is replaced by something else (e.g., water standing in for acetic anhydride), the catalyst is missing or swapped for a different substance (e.g., sodium hydroxide instead of potassium acetate), or the heating and cooling steps are missing or shown in the wrong order.
level_3: A three-necked flask, clearly distinguishable from a single-neck flask, holds benzaldehyde and acetic anhydride (both colorless liquids) and anhydrous potassium acetate (a white crystalline solid) together before heating begins; a reflux condenser is attached; a heat source is visible under the flask; a cooling step follows heating (e.g., the flame/heater turns off and the flask is left to sit).
level_4: Everything in score 3 holds, and additionally the two liquids are shown being poured into the flask rather than starting pre-filled, the solid catalyst is added as a separate, visible step rather than pre-mixed in, the reflux condenser stays vertically aligned above the center neck for the whole heating period, and the post-cooling view shows the identical flask in the identical orientation, with no repositioning or cut.
level_5: Everything in score 4 holds, and additionally the full sequence plays out in this exact, uninterrupted order: empty flask shown, the two liquids added one after another, the white solid catalyst added visibly, the condenser attached, heating begins, reflux is visible, heating stops, the flask sits undisturbed while cooling, and the same flask is shown in the final frame, with no cuts, no edits, no objects teleporting, and no shift in viewpoint.

Scientific and Causal Correctness rubric:
level_1: The reaction mixture shows no color change at all through heating and cooling (stays perfectly colorless start to finish), or it develops a color or texture inconsistent with a Perkin condensation, such as turning bright green, bubbling over violently, or foaming uncontrollably.
level_2: The mixture ends up as a clean, fully clear/colorless liquid with a separate layer of pure white crystals at the bottom, as if the free cinnamic acid product crystallized directly on cooling; or the mixture never darkens at all during reflux despite visible heating; or the reflux itself is misrepresented (condenser dry, no condensate motion, or shown inverted).
level_3: Benzaldehyde and acetic anhydride both appear as colorless liquids before mixing; the potassium acetate catalyst appears as a white crystalline solid; reflux is visibly occurring, with a continuous trickle of condensate moving down the vertical condenser; as reflux proceeds the mixture visibly darkens toward amber/brown; after cooling, the flask holds a single dark, viscous liquid mixture (or a thickened, slightly two-phase oily mixture), with no distinct layer of white crystalline solid, since the cinnamic acid product is still present as its dissolved potassium salt at this stage.
level_4: Everything in score 3 holds, and additionally the darkening begins only once heating/reflux starts and deepens the longer reflux continues; after heating stops, the mixture cools and thickens somewhat but does not deposit any clean white crystalline solid, since no hydrolysis or acidification step is shown; the color and viscosity change are continuous, not an abrupt jump.
level_5: Everything in score 4 holds, and additionally the final mixture's color is a convincing, uniform dark amber-to-brown (not colorless, not black, not an implausible bright hue); no white crystals appear anywhere in the flask at any point; the white potassium acetate solid is seen dissolving or dispersing into the liquid during heating rather than persisting as visible undissolved granules; the reflux condensate itself stays clear throughout, distinct from the darkening pot liquid.

Spatiotemporal Consistency rubric:
level_1: The flask, condenser, or reagents pop in or out of existence between frames; the flask rotates more than 90° from one frame to the next with no visible motion in between; the condenser detaches and reattaches on its own mid-sequence; the scene suddenly switches from daylight to night in a single frame; the flask's cast shadow jumps to a completely different direction with no light source shown moving.
level_2: Two or more jarring hard cuts interrupt the sequence; the flask sits in a different spot or orientation immediately after the heating-to-cooling cut; the condenser's tilt changes by more than roughly 30° between shots; the lighting visibly brightens or dims in a sudden jump; background objects change identity partway through (e.g., the bench surface becomes a different table).
level_3: At most one cut is used (either between reagent-loading and reflux, or between the end of reflux and the cooling observation), and across that cut the flask's position, orientation, the condenser's alignment, and the background all stay the same; the direction and brightness of the light on the flask stay the same for the whole video.
level_4: No cuts at all: every step plays out in one continuous take; the flask stays centered in frame; the condenser keeps a fixed, vertical, rigidly attached alignment; the light source stays put, so no shadow on the bench or flask sweeps or jumps; the background stays static and unchanging throughout.
level_5: Everything in score 4 holds, and additionally liquids being poured fall in a smooth, gravity-consistent stream with no floating droplets or upward flow; the condensate inside the condenser keeps trickling steadily downward at a constant pace; no motion blur ever obscures which object is which; the camera itself never wobbles, warps, or drifts, and it holds one fixed focal length with no zoom.