Domain: Natural Science — Chemistry
Target concept: Bromination of benzene

Video generation prompt: Benzene was poured into a three-necked flask, followed by liquid bromine, and iron powder was then added as a catalyst. After the reaction, the liquid in the flask was observed.

Evaluation guide:
(i) Target concept: Electrophilic aromatic substitution requiring catalyst-mediated activation of Br₂ to generate electrophile; minimum mechanism: bromine must be molecular (Br₂, not Br⁻ or Br•), iron must be present as Fe⁰/FeBr₃ precursor, benzene must remain intact (no addition/ring cleavage), and product must be monosubstituted bromobenzene (not dibromo or phenol).
(ii) Storyline: [Phase 1: Setup] Side-by-side view of three distinct containers: benzene (colorless), bromine (reddish-brown), iron powder (gray-black granules). [Phase 2: Addition Sequence] First, benzene poured into three-necked flask → liquid fills bottom with meniscus. Second, bromine poured in → mixes, retains reddish tint briefly. Third, iron powder added → contacts surface → immediate localized color shift. [Phase 3: Reaction Onset] Within visual continuity, entire liquid transitions to pale yellow/brown; simultaneous emergence of translucent white fumes rising vertically from surface. [Phase 4: Steady State] Fixed viewpoint holds on flask: homogeneous colored liquid, stable fume column, no bubbling/splashing, confirming controlled exothermic substitution. Visibility constraint: All phases occur in same fixed camera frame; no cuts, no occlusion, no lens flare masking key phenomena.

Manual:
Experimental Procedure
1. Place benzene (colorless liquid) and liquid bromine (reddish-brown liquid) in separate labeled containers.
2. Pour benzene into a three-necked flask.
3. Add liquid bromine to the same flask.
4. Add iron powder (gray-black granular solid) as catalyst.
Observation of Experimental Phenomena
- Immediate color change of liquid from colorless to pale yellow/light brown.
- Appearance of faint white fumes (HBr gas) above liquid surface.
Summary of Experimental Principles
Electrophilic aromatic substitution: Fe catalyzes Br₂ polarization → Br⁺ attacks benzene ring → forms bromobenzene + HBr.

Prompt Grounding rubric:
level_1: None of the required objects or actions appear: no three-necked flask, no separate benzene or bromine containers, no iron powder, and nothing shown being added to a flask. The bromination setup described in the prompt is not established at all.
level_2: A flask or a bromine container appears, but something critical is missing: the three-necked flask itself is absent, benzene and bromine are not both shown as containers, iron powder never appears, nothing is actually seen being added to the flask, or the flask's contents are never shown after the additions.
level_3: The three-necked flask is clearly present, along with a separate container of colorless benzene, a separate container of reddish-brown liquid bromine, and gray-black iron powder; benzene is poured in, then bromine, then iron powder is added, and the flask's liquid is shown afterward, matching the setup in the prompt.
level_4: All of 3, plus the spatial arrangement is preserved: the benzene and bromine containers sit near each other before pouring, the iron powder is added into the same flask, the camera stays on the flask through the additions and the post-reaction view, and no unrelated objects crowd the frame.
level_5: All of 4, plus the additions occur in the correct order (benzene first, then bromine, then iron powder), each a clearly separate, distinguishable step with no reversal or merging of steps, and the flask and its contents keep a consistent identity, with no unexplained color or label swap, from the first pour to the final observation.

Scientific and Causal Correctness rubric:
level_1: No scientifically plausible sign of reaction appears: the liquid never changes color, the bromine looks colorless instead of reddish-brown, the iron powder looks like shiny silver metal, or no fumes appear despite the exothermic reaction that should follow the iron addition.
level_2: One detail is right, such as bromine shown as reddish-brown, but the reaction sequence is broken: iron powder is added but the liquid never changes color, the color changes before iron powder is added, the final liquid turns the wrong color such as bright yellow or orange rather than pale yellow-brown, or no fumes appear at all.
level_3: Benzene is colorless, bromine is reddish-brown, and iron powder is gray-black and granular; after the additions the flask's liquid becomes pale yellow to light brown and faint white fumes rise above it, consistent with iron-catalyzed formation of bromobenzene and HBr, occurring in the order of additions, then color change, then fumes.
level_4: All of 3, plus the state changes stay physically sensible: the bromine doesn't visibly evaporate away before reacting, the iron powder stays solid rather than dissolving or melting, no unexpected precipitate or boiling appears, and the fumes appear only once iron powder has been added and persist while the flask is observed.
level_5: All of 4, plus the causal order is exact: no color change occurs before iron powder is added, the color shift begins shortly after iron contacts the liquid, fumes appear only after the color has begun to shift, the final liquid looks like one homogeneous phase with no separate bromine layer, and there is no flame, charring, or violent splashing, matching a mild, controlled substitution reaction.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the flask's contents or position differ between shots with no pour shown to explain it, iron powder is already resting on the liquid surface with no drop or sprinkle motion shown, the flask's neck or base visibly bends or warps, the color change and rising fumes both switch on and off abruptly rather than developing gradually, or the lighting abruptly shifts between bright and dark mid-sequence with no visible cause.
level_2: Major continuity flaws appear, such as at least two of: a container's position jumps between shots with no hand or pour motion, the flask rotates sharply with no visible cause, the liquid surface goes from still to turbulent and back to still for no shown reason, the benzene, bromine, and iron-powder containers are inconsistently visible from one shot to the next, or the shadows on the flask flip direction between shots with no change in the light source.
level_3: The flask and the benzene, bromine, and iron-powder containers keep consistent, traceable positions throughout; the flask does not warp or reshape; each pour or addition follows a visible path into the flask; lighting and shadow direction stay consistent throughout, with no unexplained shift; and the liquid's meniscus rises and settles naturally after each addition, with at most one brief, minor inconsistency, such as a short skip during one pour, that doesn't break the overall causal thread.
level_4: All of 3, plus the pours and additions are physically coherent: benzene and bromine flow as a continuous, viscous stream rather than floating droplets, iron powder disperses and settles onto the liquid surface without passing through the glass, and no addition starts or stops abruptly mid-motion.
level_5: All of 4, plus the whole clip reads as one continuous, physically consistent take from the first pour through the final observation: benzene, then bromine, then iron powder enter the flask in that order with plausible relative flow speeds, the resulting color change and rising fumes develop gradually rather than switching on instantly, and no step is duplicated, skipped, or shown out of order.