Domain: Engineering — Civil & Environmental Engineering
Target concept: Adding salt to the slurry water leads to the formation of distinct agglomerates and sedimentation.

Video generation prompt: Two transparent glass jars containing turbid muddy water are placed side by side; salt is added to the right jar. After both jars are briefly stirred, they are left undisturbed.

Evaluation guide:
(i) Target concept: Coagulation-induced sedimentation in colloidal suspensions via electrolyte addition.
Minimum mechanism: Presence of fine suspended clay/silt particles stabilized by surface charge; introduction of Na+ ions neutralizes surface charge; loss of colloidal stability enables aggregation under Brownian motion and gravity; aggregates grow large enough to settle visibly within observation time.
(ii)Storyline: Frame 0–2: Two identical jars filled with homogeneous turbid water, side-by-side, static. Frame 2–4: Salt poured into right jar only; no salt contact with left jar. Frame 4–6: Simultaneous stirring of both jars; liquid rotates/swirls with visible vortex. Frame 6–10: Immediate cessation of motion; left jar retains uniform cloudiness; right jar shows progressive formation of suspended clumps (agglomerates) followed by downward migration and layered separation (sedimentation), all observed from fixed frontal viewpoint with full jar visibility.

Manual:
Experimental Procedure
1. Place two identical transparent glass jars side-by-side on a flat surface.
2. Fill both jars with equal volumes of turbid muddy water (uniformly suspended fine sediment).
3. Add salt only to the right jar.
4. Briefly stir both jars identically with a clean rod.
5. Immediately stop stirring and leave both jars undisturbed.
Observation of Experimental Phenomena
After stillness: right jar develops visible particle agglomerates and sedimentation (clear upper layer + dense bottom layer); left jar remains uniformly turbid with no clumping or layering.
Summary of Experimental Principles
Adding salt to slurry water compresses the electrical double layer around suspended clay particles, reducing electrostatic repulsion and enabling van der Waals attraction—leading to particle agglomeration and accelerated gravitational sedimentation.

Prompt Grounding rubric:
level_1: No two transparent glass jars are shown; turbid muddy water is missing from one or both jars; salt is never added to either jar; the two jars are not placed next to each other; there is no stir-then-stillness sequence.
level_2: Two containers appear but they are not both transparent glass jars (e.g., a plastic bottle, an opaque bucket, or a lidded jar substituted for one); the muddy water fills only one jar or the two jars start with visibly different amounts of liquid; salt is poured into the left jar, into both jars, or into neither; the two jars are stacked, overlapping, or set far apart rather than adjacent to each other.
level_3: Two identical-looking transparent glass jars filled with turbid muddy water sit next to each other; salt is poured into the right jar only; both jars are then briefly stirred with visible swirling of the liquid; stirring stops and both jars are left undisturbed for at least 1 second; the whole sequence plays out in one continuous shot from a fixed frontal camera position.
level_4: All conditions for score 3 are met, and additionally: the two jars match in height, width, and glass thickness; the muddy water in both jars has the same starting opacity, brown-grey hue, and apparent sediment density before salt is added; the stirring tool and stirring action (rotation speed, dip depth, number of turns) look the same for both jars; stirring in the right jar stops at essentially the same moment as in the left jar, with no pause between adding the salt and starting to stir.
level_5: All conditions for score 4 are met, and additionally: the two jars are centered at the same height and spaced symmetrically with no part of either jar hidden behind the other; salt visibly enters only the right jar with no grains or dust reaching the left jar; the stirring action starts and ends at the same time in both jars; from the moment stirring stops onward there is no camera cut, zoom, pan, or refocus, and both jars stay fully visible in frame for the entire ten-second sequence.

Scientific and Causal Correctness rubric:
level_1: Neither jar shows any clumping or settling after stirring stops; the salted right jar and unsalted left jar look the same in clarity and particle distribution; nothing in the video connects the salt addition to any change in the right jar.
level_2: Clumping or settling shows up in the left (unsalted) jar instead of, or as well as, the right jar; or the same change appears equally in both jars; or clumps/settling begin before the salt is added or before any stirring happens; or the right jar visibly clears up while the left jar grows cloudier, reversing the effect the salt should have.
level_3: After the stir-then-stillness sequence, the right jar develops visible clumps of clay/silt particles and/or a settled layer with a denser band near the bottom, while the left jar stays evenly cloudy with no clumps or layering; this contrast only appears once the liquids stop moving and holds until the end of the video.
level_4: All conditions for score 3 are met, and additionally: the clumps in the right jar are clearly larger and more defined than any loose particles floating in the left jar; the right jar develops a visible boundary between a clearer upper layer and a denser lower layer; the left jar shows no clumping or layering in any frame; the change in the right jar builds up gradually over the stillness phase rather than appearing all at once.
level_5: All conditions for score 4 are met, and additionally: clumps in the right jar first hang suspended in the water column before sinking; by the end of the video the right jar has a sharp, level boundary between clear liquid above and settled sediment below; the left jar remains uniformly turbid with no visible clustering of particles at any point; the sequence of salt addition, then stirring, then stillness, then clumping, then settling is visible only in the right jar and occurs in that order.

Spatiotemporal Consistency rubric:
level_1: Between one frame and the next, a jar suddenly shows up in a different spot or at a different size than before; the light source or shadow direction shifts with no visible cause; a jar's outline bends, stretches, or warps out of shape; the muddy water's surface height jumps to a new level with no visible motion connecting the two positions; the swirling motion starts or stops instantly as if a frame were cut out; one of the jars is absent from the frame for part of the clip and then is visible again later with no explanation.
level_2: One jar drifts slightly out of its original spot or rotates a little between the stirring and stillness phases; the water surface flickers or breaks up for a frame or two; the swirling motion skips ahead or freezes momentarily instead of flowing continuously; during the stillness phase either jar shows leftover ripples, trembling, or drifting specks that make it look like it is still being disturbed.
level_3: Both jars stay in the same position and orientation for the whole video; the water surface moves continuously while stirring and settles smoothly once stirring stops; neither jar's shape distorts, no lighting jump or camera glitch occurs, and no part of either jar or its contents disappears from view or jumps to a new spot without visible motion connecting the two states; the swirling motion during stirring and its gradual slowdown afterward look physically natural.
level_4: All conditions for score 3 are met, and additionally: the swirling motion looks equally smooth and consistent in both jars (matching rotation direction and vortex shape, with no stutter or sudden reversal); the visible swirling dies down in both jars over a similar span of time after stirring stops; whatever visual change unfolds afterward in either jar builds up gradually, frame by frame, rather than popping in suddenly; no ghosting, smearing, or motion-blur artifact hides the moment a jar's appearance starts to change.
level_5: All conditions for score 4 are met, and additionally: the jars and camera hold steady with no drift or wobble for the whole clip; the water's meniscus line stays continuous and stable in both jars; there is no flare, bloom, or brightness flicker at any point; any particles that move within either jar follow a smooth, continuous path frame to frame with no sudden scattering or jump; every transition in the video (swirling to stillness, and whatever the liquid's appearance does afterward) unfolds as one uninterrupted, physically continuous motion.