Domain: Natural Science — Chemistry
Target concept: Reaction between carbon and concentrated sulfuric acid

Video generation prompt: A hard glass test tube contains black carbon powder. An excess of concentrated sulfuric acid is added, and the test tube is heated with an alcohol lamp. The gas generated is led through a delivery tube into a fuchsin solution.

Evaluation guide:
(i) Target concept: Visual confirmation of SO₂ gas production via redox reaction between carbon and hot concentrated sulfuric acid, verified by fuchsin decolorization.
Minimum mechanism: Carbon must be solid and black; concentrated H₂SO₄ must be liquid and colorless; heating must initiate gas evolution; gas must travel physically through tube; SO₂ must contact fuchsin to cause decolorization via a heat-labile addition reaction. The fading is reversible (the magenta color returns if the bleached solution is later reheated), which is precisely what distinguishes SO₂'s bleaching from chlorine's permanent bleaching, and no alternative gases (e.g., CO₂) cause this effect.
(ii)Storyline: Frame 1–2: Static shot showing hard glass test tube containing black carbon powder and colorless concentrated sulfuric acid. Frame 3: Alcohol lamp flame approaches and contacts test tube base. Frame 4: Bubbles/gas emerge from acid-carbon mixture. Frame 5: Gas flows visibly through rigid delivery tube. Frame 6: Gas enters fuchsin solution causing localized decolorization at inlet. Frame 7–10: Decolorization spreads progressively through solution, all while test tube remains upright, lamp stays in place, and no object violates spatial continuity. Perspective: Fixed frontal view, eye-level, full-scene framing; no cuts, no zoom, no POV shifts.

Manual:
Experimental Procedure
1. Place black carbon powder into a hard glass test tube.
2. Add excess concentrated sulfuric acid to cover carbon completely.
3. Heat the bottom of the test tube with an alcohol lamp flame.
4. Connect a delivery tube from test tube mouth to fuchsin solution.
Observation of Experimental Phenomena
- Gas evolves from mixture only during heating.
- Gas passes continuously through delivery tube.
- Fuchsin solution decolorizes (loses magenta/pink color) after gas enters it.
Summary of Experimental Principles
Carbon reduces concentrated H₂SO₄ to SO₂ gas; SO₂ decolorizes fuchsin solution via addition reaction — confirming SO₂ generation.

Prompt Grounding rubric:
level_1: No black carbon powder, no concentrated sulfuric acid, no hard glass test tube, no alcohol lamp, no delivery tube, and no fuchsin solution appear anywhere in the frame.
level_2: A few of the six required items appear (e.g., a tube and a flame) but most are missing or wrong: the liquid in the tube looks colored or milky instead of colorless concentrated H₂SO₄, the heat source is not a lamp/flame, or no tube connects the reaction vessel to a second container.
level_3: All six items are visible and identifiable (the hard glass test tube, black carbon powder inside it, concentrated sulfuric acid covering the carbon, an alcohol lamp under the tube, a delivery tube from the tube's mouth, and a separate container of magenta fuchsin solution receiving the delivery tube's far end), arranged in a plausible bench layout.
level_4: The carbon powder is fully contained within the test tube with none spilled outside it, the sulfuric acid fully covers the carbon with no dry powder exposed above the liquid line, the delivery tube's outlet sits below the fuchsin solution's surface, and the alcohol lamp's flame visibly touches the tube's lower section, with only one small setup flaw remaining, such as the delivery tube looking too thin or the fuchsin container mismatched in style to the rest of the glassware.
level_5: The test tube stands upright, the delivery tube runs straight between the two vessels with no odd kinks, the fuchsin container is a clear vessel filled to roughly mid-height with visibly pink/magenta liquid, the alcohol lamp shows a flame with a bluish base and yellow tip, and the glass, liquid, powder, and flame all keep materials that look like what they are (transparent glass stays transparent, carbon stays a dull black solid, acid stays a clear liquid) with no prop looking out of place.

Scientific and Causal Correctness rubric:
level_1: Nothing shown connects to the carbon + hot concentrated H₂SO₄ reaction (no gas bubbles, no vapor, no change in the fuchsin), or what is shown contradicts the chemistry (e.g., the fuchsin turns blue instead of fading, or the carbon visibly dissolves like a solid dissolving in water).
level_2: A causal step is shown out of order: the fuchsin loses color before any gas has reached it, gas bubbles appear before the flame has touched the tube, or the carbon disappears without residue while no gas is visibly produced.
level_3: Gas is only seen forming after the flame contacts the test tube, it travels visibly through the delivery tube, and the fuchsin only starts fading after gas has entered it, with no contradictory event such as the acid changing color or the fuchsin fading before gas arrives.
level_4: Gas production tracks the heating precisely (it starts once the flame is applied and stops once the flame is pulled away), the fuchsin's fading begins right where the delivery tube's outlet meets the liquid and spreads outward from there, the carbon stays visibly black and grainy throughout (no glowing, melting, or dissolving), and the fuchsin does not regain any pink color once faded.
level_5: The gas stream flows at a steady, continuous rate rather than in irregular bursts, the fuchsin's color loss spreads evenly outward from the inlet without splashing or streaky patches, the carbon keeps a sharp, high-contrast black granular texture against the clear acid, the acid itself stays clear and colorless with no charring, and no soot or scorch marks appear on the tube's inner walls.

Spatiotemporal Consistency rubric:
level_1: The test tube, delivery tube, or fuchsin container is absent from one frame and present in the next with no motion carrying it there, the delivery tube's connection to either vessel breaks and reforms with no motion shown, the room's lighting swings between bright and dark with no visible cause, the flame flickers out and reignites instantly with no gradual dimming, or the glass tube visibly deforms or melts instead of holding its rigid shape.
level_2: Two or more of the following occur: the test tube rotates by a large angle with nothing tilting it, the delivery tube bends sharply and then straightens on its own, the flame's size doubles from one frame to the next, the fuchsin's liquid level rises or drops in a sudden jump rather than gradually, or the shadows on the bench swing to a different direction with no light source moving.
level_3: The test tube, delivery tube, lamp, and fuchsin container keep the same relative positions throughout, the lighting stays even in direction and brightness, and nothing appears out of proportion or misplaced, but one small blemish remains, such as a brief stutter in the gas bubbles' motion or a momentary dimming of the flame that quickly recovers.
level_4: The flame sways gently but never snaps between positions, the gas visible inside the delivery tube shows a subtle, continuously changing haze rather than looking frozen or strobing, the acid's surface ripples smoothly as it's heated, and the fuchsin's surface only moves where gas bubbles disturb it, with no floating debris or unnatural buoyancy.
level_5: The whole bench-top scene reads as one continuous, undistorted shot: no fisheye or skewed perspective, no dropped or duplicated frames, no sudden change in playback speed, and no stray flash of light or shadow that doesn't match the lamp's flame; the glass tube shows the faint bending of the background visible through it that real glass produces, and the flame's glow stays soft and steady without flicker or a colored fringe at its edges.