Domain: Natural Science — Chemistry
Target concept: Insert a glowing splint into an oxygen bottle, and it will immediately reignite; this phenomenon does not occur in air.

Video generation prompt: Prepare two identical-looking bottles side by side: one filled with oxygen and one filled with ordinary air, both clearly labelled. Ignite a wooden splint until it is red-hot but not burning with a flame, then insert the red-hot splint into the oxygen bottle and remove it again. Re-ignite the splint to the same red-hot state and insert it into the air bottle, then remove it again. Demonstrate a clear, step-by-step procedure for both bottles, using appropriate laboratory equipment and maintaining proper laboratory safety posture.

Evaluation guide:
Target concept: Oxygen’s role as a combustion supporter, specifically, that high-concentration O₂ enables *instantaneous, self-sustaining reignition* of a red-hot carbon source, whereas ambient air (21% O₂) does not. Minimum mechanistic assumption: Combustion requires fuel (carbonized wood), heat (red-hot state), and oxidizer (O₂), and reaction rate scales nonlinearly with O₂ partial pressure. Phased storyline: (1) Preparation: Splint ignited → flame extinguished → verified red-hot state (no flame, uniform glow); (2) Causal trigger: Splint enters O₂-rich environment → immediate exothermic oxidation → visible flame ignition (≤0.3 s latency); (3) Contrast verification: Identical splint enters air → no flame, only thermal decay (glow fades); (4) Visibility constraint: All critical states (red-hot tip, flame onset, absence of flame in air) must be frontally framed, well-lit, and free of occlusion, with no hand/tongs obscuring splint tip during insertion; perspective must enable unambiguous discrimination of flame vs. glow.

Manual:
I. Basic Demonstration Information
Demonstration Title: Glowing Splint Test for Oxygen Detection
Subject: Natural Science - Chemistry - Gases and Combustion
Demonstration Purpose: To visually confirm the presence of concentrated oxygen by observing the immediate reignition of a red-hot (glowing) wooden splint upon insertion into an oxygen-filled bottle — a phenomenon that does not occur in air; to reinforce the principle that oxygen supports combustion, and its concentration determines combustion intensity.

II. Demonstration Carrier/Equipment
Core Carrier: Oxygen-filled gas bottle (cylindrical, clear glass or thick-walled plastic, labelled ‘O₂’, upright, with visible condensation or refractive shimmer indicating high-density gas); wooden splint (12 cm × 0.5 cm, dry, untreated).
Auxiliary Equipment: Bunsen burner or alcohol lamp (for ignition); heat-resistant tongs; safety goggles, lab coat, and flame-resistant gloves; control air bottle (identical in size/shape/label ‘air’); stable lab bench with non-flammable surface.

III. Demonstration Content Description
Layout: Place O₂ bottle and air bottle side-by-side on bench, 20 cm apart, both upright and labelled. Demonstrator stands facing bottles, wearing full PPE.
State Control: Ignite splint fully, then gently blow out flame to leave *only* a uniformly glowing red-hot tip (no flame, no smoke, cherry-red incandescence). Hold splint horizontally with tongs, 15 cm from tip.
Sequence: (1) Show glowing splint clearly; (2) Insert splint vertically into O₂ bottle to depth of ~8 cm; (3) Observe *instantaneous* reignition (≤0.3 s) with bright, conical flame (2–3 cm); (4) Withdraw splint cleanly; (5) Repeat identical procedure with air bottle — show *no reignition*, only brief intensification then fading of glow.

IV. Observation of Core Phenomena
O₂ Bottle Phenomenon: Immediate, vigorous reignition upon entry; flame is bright yellow-white, steady, conical, lasts 1.0–1.5 s while immersed; splint tip remains intact (no rapid consumption).
Air Bottle Phenomenon: No flame emerges; red glow may brighten momentarily (due to transient heating) then dims steadily within 0.8 s; no combustion sustained.
Visual Contrast: Flame presence/absence is binary, unambiguous, and temporally locked to bottle identity — direct visual proof of oxygen’s role as a combustion supporter.

V. Summary of Key Knowledge Points and Principles
Core Concept: Oxygen is a reactive nonmetal gas essential for combustion; its high concentration (≈100% in bottle vs. 21% in air) lowers the activation energy for oxidation, enabling rapid, self-sustaining combustion of hot carbon.
Principle Link: Reignition occurs because the glowing splint’s hot carbon surface reacts exothermically with O₂: C(s) + O₂(g) → CO₂(g) + heat. In air, reaction rate is too slow to sustain visible flame; in pure O₂, it accelerates instantly.
Safety Note: Pure O₂ increases fire risk — never use near oils/grease; always use tongs; never seal bottle during test.

VI. Demonstration Precautions
- Splint must be *glowing*, not flaming — flame indicates incomplete extinction and invalidates test.
- Bottle must be upright and stable — tilting causes gas leakage and false-negative results.
- Lighting must be neutral (no colored filters) to ensure accurate perception of red-hot vs. flame colors.
- Video must capture full insertion-to-withdrawal in one continuous shot — no cuts — to preserve causal integrity.

Prompt Grounding rubric:
level_1: Neither the oxygen bottle nor the air bottle is shown; no wooden splint present; no ignition, no red-hot state, no insertion action into either bottle; no lab setting or safety gear visible; the scene is unrelated (e.g., an empty benchtop, a plant, or a digital interface).
level_2: Only one bottle appears (oxygen or air) and it is unlabelled or clearly not gas-filled (e.g., an empty transparent jar); the splint is visibly flaming or cold rather than red-hot; no insertion into any bottle is shown; the demonstrator's posture is unsafe (e.g., face over the bottle mouth, no goggles, sleeves loose near the flame).
level_3: Both an oxygen bottle and an air bottle are present and visibly gas-filled (e.g., faint condensation, legible 'O2'/'air' labels); a splint is ignited and charred but not clearly glowing red-hot (the ember is not distinctly visible); insertion into at least one bottle occurs but is partial or ambiguous (the splint tip barely crosses the bottle mouth); goggles are worn but gloves are missing or the stance is slightly hunched.
level_4: The oxygen bottle is labelled 'O2' and the air bottle is labelled 'air', both upright with visible gas cues (e.g., slight haze); the splint is fully ignited then extinguished to a uniform red-hot ember (no flame) before each insertion; both insertions are full-depth and centered, performed as separate, clearly sequenced actions; the demonstrator wears goggles, lab coat, and heat-resistant gloves throughout.
level_5: All core elements match: (i) an 'O2'-labelled bottle and an 'air'-labelled bottle, matching cylindrical shape and size, both upright on a stable surface, with the O2 bottle showing subtle condensation or refraction cues of denser gas; (ii) the wooden splint (roughly 10-15 cm) is ignited then allowed to self-extinguish to a sustained glowing red-hot tip (no flame, no smoke) before each insertion; (iii) each insertion is smooth, vertical, roughly 8 cm deep, held briefly, then cleanly withdrawn, performed once for the oxygen bottle and once, with a freshly re-glowed splint, for the air bottle; (iv) the demonstrator maintains full lab safety throughout: goggles, covered sleeves, tongs (not fingers) holding the splint, and a stable stance.

Scientific and Causal Correctness rubric:
level_1: No reignition occurs anywhere; the splint in the oxygen bottle goes out or is unchanged; or a bottle labelled 'oxygen' behaves like plain air (no flame at all); the phenomenon contradicts chemistry (e.g., the splint in the air bottle bursts into flame while the one in the oxygen bottle does not).
level_2: The splint in the oxygen bottle reignites only after it is pulled back out, not while still inside, or only after a delay of more than 2 seconds; or the splint in the air bottle also reignites into a full flame, contradicting the fact that ordinary air cannot support this reignition.
level_3: The splint reignites into a visible flame while inside the oxygen bottle, but the flame is faint, sputtering, or goes out almost immediately; the splint in the air bottle shows some response, but there is no clear visual contrast between the two outcomes (both look similar, or the air-bottle result is ambiguous).
level_4: The splint in the oxygen bottle reignites promptly upon insertion into a steady, bright flame that persists while it stays immersed; the same red-hot splint, reinserted into the air bottle, shows no comparable flame, at most a brief brightening of the glow that then fades; the two outcomes are clearly distinguishable side by side.
level_5: The causal contrast is unambiguous and complete: (i) the red-hot splint bursts into a sustained, bright flame promptly upon entering the oxygen bottle and keeps burning while immersed; (ii) the flame shrinks and goes out as the splint is withdrawn from the oxygen bottle; (iii) the splint, re-glowed to the same red-hot state and inserted into the air bottle, shows no flame at any point, only its red glow, which fades rather than intensifies; (iv) the pairing makes the underlying chemistry visually self-evident: only the oxygen-rich bottle supports renewed combustion of the glowing splint.

Spatiotemporal Consistency rubric:
level_1: The bottles or the splint appear in mismatched shots with inconsistent scale or lighting; the splint appears already aflame in the same frame as its insertion, with no visible ignition trigger; a hand holding the splint appears or disappears abruptly between frames; a flame rises sideways or floats free of the splint, ignoring gravity and airflow.
level_2: A bottle visibly wobbles or shifts during insertion; the splint shakes excessively; a flame points in a direction inconsistent with an upright bottle; the lighting changes noticeably partway through the sequence; a hand enters the frame without having been shown approaching; the splint appears red-hot before its ignition is shown.
level_3: Only minor inconsistencies remain: a bottle sits slightly tilted, the splint's insertion angle wanders somewhat from vertical, a flame flickers but stays anchored at the splint tip, and the lighting is broadly consistent apart from a minor shadow shift on the hand; the action still reads as one continuous take, though the pacing feels a little rushed.
level_4: Both bottles stay visibly upright and stationary throughout their respective insertions; the splint enters each bottle close to vertically; any flame rises with a natural upward curl centered on the splint tip; the lighting stays even across the scene with no sudden glare; hand movement is smooth and plausible (elbow bent, wrist steady); each insertion-to-withdrawal action plays out in one continuous shot without cuts.
level_5: The full sequence holds together with no visible break: (i) each bottle stays in the same position and orientation throughout its insertion, with no perceptible drift, jump, or background change; (ii) the splint's red-hot tip holds a steady glow right up to contact, after which any flame appears within the same visible moment rather than after a noticeable pause; (iii) a flame, if present, grows and shrinks smoothly as the splint is inserted and withdrawn, with no sudden appearance or disappearance; (iv) the demonstrator's arm and hand motion stays continuous: shoulder, elbow, and wrist move in a single natural arc with no sudden freezes; (v) neither bottle, splint, nor demonstrator ever jumps instantly to a different position or state. Every change unfolds through visible, continuous motion.