Domain: Natural Science — Chemistry
Target concept: The two monomers are miscible and gradually thicken upon mixing, forming a uniform, light yellow viscous copolymer without phase separation.

Video generation prompt: The copolymerization of styrene and butadiene monomers, initiated with benzoyl peroxide and gentle heating, was carried out in a transparent reactor, with the homogeneity and viscosity changes of the system being recorded.

Evaluation guide:
(i) Target concept: Benzoyl-peroxide-initiated radical copolymerization of miscible styrene and butadiene, producing progressive viscoelastic homogenization under mild heating.
Minimum mechanism: Styrene and butadiene are miscible from the start (no barrier to mixing), but copolymerize only once benzoyl peroxide is added and the mixture is heated, generating free radicals that build entangled copolymer chains; this raises viscosity and shifts the color toward light yellow while the liquid stays a single, continuously clear phase throughout.
(ii)Storyline: Frame 1–2: Two colorless liquids (styrene, butadiene) in labeled containers sit beside a transparent reactor on a hot plate/water bath, with a small container of benzoyl peroxide nearby. Frame 3–4: The monomers and initiator are poured into the reactor, heating begins, and the liquids touch at a visible interface. Frame 5–7: Stirring dissolves the interface and the liquid becomes one continuous, still-fluid phase. Frame 8–9: The color deepens smoothly from colorless to light yellow while the stirrer visibly slows as viscosity rises. Frame 10: A fully homogeneous, light yellow, viscous mass fills the reactor with a stable meniscus and no flow; fixed side view, no cut, no zoom, no occlusion.

Manual:
Experimental Procedure
1. Place colorless styrene and butadiene monomers into a transparent reactor.
2. Add a small measured amount of benzoyl peroxide (a radical initiator) to the monomers.
3. Place the reactor on a heat source (e.g., a hot plate or warm water bath) and stir while warming gently to start the copolymerization.
Observation of Experimental Phenomena
- The two initially separate colorless liquids merge into a single continuous phase with no droplets or layers.
- As heating and stirring continue, the mixture's color shifts gradually from colorless to light yellow while its viscosity steadily increases, shown by a slowing stirrer and a thickening meniscus.
- The final product is a homogeneous, light yellow, viscous copolymer that no longer flows on its own.
Summary of Experimental Principles
Styrene and butadiene are miscible liquids that do not react on simple mixing; adding benzoyl peroxide and applying gentle heat generates free radicals that drive their copolymerization, producing a uniform, light yellow, viscous copolymer without phase separation.

Prompt Grounding rubric:
level_1: No transparent reactor is shown; no styrene or butadiene monomers appear; no benzoyl peroxide or heat source (hot plate or water bath) is present; no mixing or heating action occurs; no color or viscosity change is visible anywhere.
level_2: A transparent reactor and the two colorless monomers are visible, but they are never combined: no benzoyl peroxide is added, no heating occurs, and no mixing action takes place; the liquids remain separate with no color or thickening change.
level_3: Colorless styrene and butadiene are visibly poured into a transparent reactor along with benzoyl peroxide, and the reactor is placed on or near a heat source with a mixing action shown; by the final frame the liquid is a single continuous phase, but it lacks a clear light-yellow color shift or visible thickening.
level_4: All 3-score elements are present, and the reactor visibly stays on the heat source with stirring throughout; the two colorless liquids merge into one continuous phase without ever splitting into separate layers or droplets; by the end the liquid has taken on a light-yellow color and appears distinctly more viscous (e.g., slower stirrer, thicker-looking flow) than at the start; all objects match the described types and stay in the arrangement shown at the outset.
level_5: Exactly the described objects (the two colorless monomers, the benzoyl peroxide initiator, the transparent reactor, and the heat source) appear in a fixed side-by-side arrangement; heating and mixing begin promptly once the monomers and initiator are combined; the liquid progresses smoothly from two colorless streams to a single light-yellow, visibly thicker mass that keeps a stable meniscus and stops flowing by the final frame, with no extra props, no camera-angle change, and no jump in the setup.

Scientific and Causal Correctness rubric:
level_1: The final liquid stays colorless, turns white/opaque, or separates into visible layers/droplets; its viscosity never increases; or the color that appears is blue, green, or dark brown rather than light yellow. Any of these means the depicted chemistry contradicts a miscible, initiator-driven copolymerization.
level_2: The two monomers never fully blend (a persistent interface or cloudy boundary remains); or a light-yellow color and thicker consistency appear before the benzoyl peroxide and heat are introduced; or the liquid still pours and flows as easily as water at the final frame. Any of these breaks the initiator-driven, gradually-thickening reaction chain.
level_3: After benzoyl peroxide and heat are applied, the two colorless liquids merge into one continuous phase and the mixture visibly thickens over the course of heating (e.g., stirrer slows, resistance to stirring increases); by the end the liquid is light yellow with no layering, but the thickening is not sustained to the very last frame, or the color change looks abrupt rather than gradual.
level_4: All 3-score elements hold, and in addition the color change from colorless to light yellow and the viscosity increase both progress smoothly and continuously once heating starts, with no reversal (the liquid never turns clear again or thins back out) and no unexplained flickering of color.
level_5: From the moment heating and mixing begin, the liquid thickens and yellows in one continuous, uninterrupted progression with no stalling, reversal, or sudden jumps; by the final frame the mass is uniformly light yellow, clearly more resistant to stirring/flow than the starting monomers, holds a stable meniscus, and shows no droplets, streaks, or two-tone patches anywhere in the reactor.

Spatiotemporal Consistency rubric:
level_1: The reactor or hot plate changes position or appearance between shots without any pouring or moving action shown; the monomers, initiator, or final copolymer appear or vanish with no visible cause; the room lighting jumps abruptly partway through the sequence.
level_2: The reactor and heat source stay put, but the monomer or initiator containers appear in frame without ever being carried in; the stirring motion skips or reverses without cause; the finished light-yellow mass appears suddenly with no visible transition from the starting liquids.
level_3: The reactor, hot plate, and containers keep consistent positions relative to each other throughout; stirring is continuous and unbroken; the thickening of the liquid is shown as a smooth visual progression (e.g., the stirrer visibly slows, the meniscus rises gradually) rather than as a single discrete jump.
level_4: The camera viewpoint and the reactor's geometry and transparency stay constant throughout; the monomers are added and mixed in one unbroken sequence; the rising viscosity shows up as consistent physical behavior (no splashing, no sudden rebound of the stirrer, no floating fragments), and the motion of stirrer and liquid is directionally consistent from start to finish.
level_5: The reactor, hot plate, and labels stay in the same place and shape across the whole sequence with no jitter or drift; stirring and thickening unfold at a steady, uninterrupted pace with no frame skips, freezes, or reversed motion; shadows and reflections on the glass shift smoothly and only as much as the liquid's rising level and color would naturally cause, with no unexplained flashes or mismatched highlights.