Domain: Engineering — Food and Bioprocess Engineering
Target concept: Ion interaction shielding: latex colloids (not milk) aggregate upon salt addition

Video generation prompt: Both glass cups are filled with a milky-white latex colloidal suspension; add a spoonful of salt to the cup on the right and stir, while keeping the cup on the left unchanged. Place both cups within the field of vision.

Evaluation guide:
(i) Target concept: Electrolyte-induced destabilization of an electrostatically stabilized colloid (surface-charge screening / double-layer compression).
Minimum mechanism: The liquid in both cups must be a dispersed latex (polymer-particle) suspension whose particles are kept apart mainly by electrostatic surface-charge repulsion, without added steric stabilizers; the salt stirred into the right cup must dissociate into Na⁺/Cl⁻ ions that compress the particles' electrical double layer and screen their surface charge; once this repulsion is sufficiently reduced, short-range van der Waals attraction can pull particles together into visible clumps.
(ii)Storyline: Frame opens on a static wide shot showing two identical glass cups side-by-side, both filled with the same milky-white latex suspension. A spoon enters frame from bottom-right, holding visible salt crystals, and deposits them into the right cup. The spoon stirs the right cup only: continuous rotational motion with a visible vortex and surface deformation. The left cup remains completely still, with no hand proximity and no shadow interference. After stirring, the right cup develops visible particulate clumps or flocs (heterogeneous clusters rather than a uniform haze) that may settle gradually; the left cup retains its original smooth, homogeneous appearance and surface meniscus. The entire sequence is viewed from a fixed frontal angle, with no cut, zoom, or pan.

Manual:
Experimental Procedure
1. Place two identical transparent glass cups side-by-side in a fixed frame.
2. Fill both cups to the same level with the same diluted, milky-white latex (polymer) colloidal suspension.
3. Add one spoonful of granular table salt to the right cup only.
4. Stir the right cup continuously for ~3 seconds; leave the left cup undisturbed.
Observation of Experimental Phenomena
The right cup develops visible particulate clumps/flocs suspended in the liquid; the left cup remains uniformly smooth and homogeneous with no texture change.
Summary of Experimental Principles
The latex particles in the suspension carry a net surface charge and, without added steric stabilizers, are kept dispersed mainly by electrostatic (double-layer) repulsion between particles. Dissolved Na⁺/Cl⁻ ions from the added salt compress this electrical double layer and screen the particles' surface charge; once repulsion is sufficiently reduced, short-range van der Waals attraction dominates and particles clump together (flocculate), producing visible turbidity and particulate clusters. This is the same double-layer-screening mechanism used industrially to coagulate rubber latex with electrolytes, and it is distinct from dairy milk, whose casein micelles resist plain salt addition because they are stabilized largely by a steric 'hairy layer' rather than by charge alone.

Prompt Grounding rubric:
level_1: Neither of the two glass cups is visible, or neither contains any liquid, or no spoon or salt-adding action is shown, or the two cups are not placed side-by-side, or no stirring action occurs and no cup is shown remaining undisturbed.
level_2: Two glass cups sit side-by-side, but at least one holds a liquid that doesn't read as an opaque, milky-white suspension (e.g., clear water, a colored juice, or a liquid with an inconsistent texture); a spoon appears but never contacts the right cup; the left cup is missing or is not visually distinguishable from the right cup.
level_3: Two transparent glass cups sit side-by-side in the same shot, both filled with the same opaque, milky-white liquid consistent with the latex suspension established at the start; a spoon enters or is held only near the right cup and never approaches the left cup; the left cup stays motionless and unchanged throughout; stirring motion occurs only in the right cup.
level_4: All level-3 conditions are met, and additionally: the spoon fully enters the right cup before any stirring begins; the stirring motion is continuous and confined entirely to the right cup; the left cup shows no interaction at all: no hand nearby, no shadow crossing it, no motion cue; both cups stay fully visible and in a fixed position throughout the shot.
level_5: All level-4 conditions are met, and additionally: the spoon visibly carries solid granular salt (not a liquid or a powder haze) before entering the right cup; the salt is clearly released into the right cup before stirring starts; the spoon's contents are never ambiguous against the background; both cups keep the same fill level, shape, and orientation from start to finish, with no cropping or repositioning of either cup.

Scientific and Causal Correctness rubric:
level_1: No state change occurs in either cup: both look identical before and after; there is no clumping, cloudiness change, or phase separation in either cup; the liquid stays uniformly smooth and milky-white in both; no visible contrast develops between them.
level_2: A visible change occurs in only one cup, but it doesn't match salt-induced flocculation (e.g., a color shift toward yellow or blue, foaming or bubble formation, or the liquid becoming visibly clearer or thinner rather than clumpier); or the visible change appears in the left, untouched cup instead of the right one.
level_3: The right cup shows a visible texture change (patches or an overall increase in graininess or clumpiness distinct from its starting appearance), while the left cup stays uniformly smooth and milky-white with no texture change; this change appears during or after the stirring in the right cup and does not reverse or clear up by the end of the shot.
level_4: All level-3 conditions are met, and additionally: the change in the right cup reads as distinct particulate clumps or flocs rather than a uniform haze, consistent with particles sticking together rather than dissolving further; these clumps look denser near the bottom or center of the cup after stirring; the left cup shows no clumping, no settling lines, and no boundary distortion anywhere.
level_5: All level-4 conditions are met, and additionally: the clumps in the right cup become visible during stirring or shortly after it ends, and they grow larger or more numerous over the remainder of the shot rather than breaking apart or dispersing; no motion blur hides the shape of the clumps; the left cup's surface meniscus and reflectivity look the same at the end of the shot as they did at the start.

Spatiotemporal Consistency rubric:
level_1: Either cup vanishes and reappears, or jumps to a new position, between moments; the spoon jumps from one spot to another with no visible path between them; the lighting flips suddenly, such as a flash or a hard shadow wipe, partway through; a cup's rim or wall visibly warps or breaks apart; the liquid surface flickers erratically or blinks out and back; the camera view rotates or zooms during the shot.
level_2: The spoon disappears for a couple of frames and then reappears already inside the cup, skipping its entry motion; one of the cups shifts sideways or up/down by more than 10% of its own height between moments; the liquid surface jumps to a new shape rather than deforming continuously; the spoon's shadow shows up on the left cup while the spoon itself is still over the right cup.
level_3: Both cups keep a consistent shape, position, and orientation throughout the shot, with no sudden jump or repositioning; the spoon's motion reads as one continuous action (approaching, entering the right cup, stirring, then withdrawing) without skipping any of these stages; the liquid surface in the right cup deforms smoothly while being stirred and settles smoothly afterward; lighting stays steady with no flicker or shadow that jumps to an implausible location.
level_4: All level-3 conditions are met, and additionally: the spoon keeps a consistent size, opacity, and perspective as it moves, with no sudden scaling or edge shimmer; both cups' walls show stable, physically plausible refraction and reflection of the liquid inside them; the meniscus curve at the top of each liquid stays smooth and unbroken; nothing pops in or out of view between frames.
level_5: All level-4 conditions are met, and additionally: the background stays static while only the spoon and the stirred liquid move, giving a consistent sense of depth; the liquid surface motion in the right cup visibly matches the direction and speed of the stirring, showing a rotating swirl that persists rather than freezing or reversing; no frame shows duplicated or ghosted copies of the spoon or cups; the spoon is always occluded correctly by the cup wall, such that its handle never appears to pass in front of the wall when it is actually behind it.