Domain: Natural Science — Chemistry
Target concept: Reaction between sodium silicate solution and dilute hydrochloric acid

Video generation prompt: A test tube containing 5 mL of colorless sodium silicate solution was treated with dilute hydrochloric acid using a pipette.

Evaluation guide:
(i) Target concept: Acid-induced sol-gel transition of aqueous sodium silicate via in situ formation of polymeric hydrated silica.
Minimum mechanism: The reaction must proceed via protonation of silicate anions leading to condensation into Si–O–Si networks; this requires aqueous environment, absence of strong oxidizers/reducers, and no competing precipitation (e.g., chloride salts remain soluble and invisible).
(ii)Storyline: [Frame 0–2] Static shot: upright test tube filled with still, colorless liquid (sodium silicate solution). [Frame 3–4] Pipette enters frame from top, aligned vertically above test tube mouth. [Frame 5–6] Liquid stream emerges from pipette tip and makes contact with solution surface. [Frame 7–8] Immediate localized cloudiness at impact site, expanding downward as gel forms. [Frame 9–10] Entire solution transforms into homogeneous, non-flowing white gel; meniscus flattens and stiffens. Perspective: Fixed frontal view, centered on test tube; full test tube visible from base to rim; pipette tip must be within frame during delivery; no occlusion of reaction zone.

Manual:
Experimental Procedure
1. Place a clean, dry test tube upright on a stable surface.
2. Add 5 mL of colorless sodium silicate solution into the test tube.
3. Using a clean pipette, carefully deliver dilute hydrochloric acid dropwise into the solution.
Observation of Experimental Phenomena
A white, cloudy, gelatinous precipitate forms immediately upon acid contact, progressively increasing opacity and viscosity; the mixture becomes semi-solid and does not flow freely.
Summary of Experimental Principles
Sodium silicate reacts with dilute HCl to form silicic acid (H₄SiO₄), which dehydrates spontaneously into hydrated silica gel — a colloidal network that immobilizes water, causing visible opacification and loss of fluidity.

Prompt Grounding rubric:
level_1: No test tube visible; no sodium silicate solution present; no pipette present; no hydrochloric acid application action shown; none of the required objects or actions from the posted_prompt appear.
level_2: At least one required object appears (e.g., test tube OR pipette), but the test tube does not contain colorless liquid, or the pipette is not shown delivering liquid into the test tube, or the sequence is reversed (e.g., pipette appears before test tube is shown), or more than one container is present without clear identification of the target test tube.
level_3: A single upright test tube containing a colorless liquid is visibly present; a pipette is present and shown contacting the test tube opening or interior; dilute hydrochloric acid is delivered (liquid emerges from pipette tip toward test tube); all three core objects (test tube, sodium silicate solution, pipette) are present and spatially coherent in one fixed scene.
level_4: All conditions for score 3 are satisfied AND the pipette delivers liquid continuously (not as a single static frame or abrupt cut), the test tube remains stationary and upright throughout, and the liquid delivery occurs exclusively into the test tube (no spillage outside, no secondary containers involved).
level_5: All conditions for score 4 are satisfied AND the pipette is visibly held vertically or near-vertical above the test tube mouth, the liquid stream enters the test tube without splashing or rebound, the test tube maintains consistent orientation and position across all frames, and no extraneous objects (e.g., gloves, labels, other reagents) enter the frame at any time.

Scientific and Causal Correctness rubric:
level_1: No observable phenomenon matching the reaction: no gel formation, no opacity change, no solid-like structure appearing; liquid remains fully transparent and fluid throughout; or a physically impossible phenomenon occurs (e.g., immediate explosion, color change to blue/red, bubbling, gas evolution).
level_2: A state change occurs but is scientifically incorrect: e.g., liquid turns colored (yellow/pink), forms bubbles, separates into layers, evaporates, or solidifies into a brittle crystal — none of which occur in the actual Na₂SiO₃ + HCl reaction; or the change appears before acid addition.
level_3: A white, cloudy, gelatinous precipitate appears inside the test tube after acid delivery begins; the liquid transitions from fully transparent to increasingly opaque and viscous; the precipitate remains suspended or settles slowly without dissolving, matching the expected formation of silicic acid gel.
level_4: All conditions for score 3 are satisfied AND the cloudiness appears only after the first contact between acid and silicate solution (no pre-existing turbidity), the gel forms progressively (increasing density over time), and no contradictory phenomena co-occur (e.g., no simultaneous color shift, no phase separation, no effervescence).
level_5: All conditions for score 4 are satisfied AND the gel exhibits characteristic non-Newtonian behavior: it retains shape when undisturbed (no flow under gravity alone), shows surface tension-defined meniscus distortion upon settling, and maintains uniform whiteness (no yellowing, browning, or translucency gradients); no trace of clarity remains in the bulk post-reaction.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal discontinuity: test tube disappears/reappears; pipette jumps location; liquid materializes without motion path; lighting changes abruptly between frames; camera angle shifts >30° mid-sequence; structural break (e.g., test tube cracks then reforms).
level_2: Multiple minor discontinuities: e.g., pipette tip vanishes for ≥2 consecutive frames, test tube wobbles violently with inconsistent shadow, liquid stream flickers on/off without motion continuity, or background elements teleport; at least two of these occur.
level_3: Test tube remains in fixed position and orientation; pipette moves smoothly from approach to contact; liquid stream appears as a continuous visual trajectory from pipette tip into test tube; lighting and shadows remain consistent; no object clipping, warping, or morphing observed.
level_4: All conditions for score 3 are satisfied AND the pipette motion follows a single unbroken path (no hesitation, reversal, or pause mid-descent), the liquid stream maintains consistent thickness and opacity from origin to impact, and the test tube’s meniscus deforms gradually and plausibly upon liquid entry (no instantaneous level jump).
level_5: All conditions for score 4 are satisfied AND every frame shows physically plausible motion: pipette acceleration/deceleration is visually smooth (no strobing or jerkiness), liquid stream exhibits natural cohesion (no pixelated breaks or unnatural segmentation), test tube wall reflects ambient light consistently, and no inter-frame parallax mismatch occurs between foreground and background elements.