Domain: Natural Science — Chemistry
Target concept: Hot water recrystallization of impure copper sulfate crystals

Video generation prompt: In the laboratory, the impure copper(II) sulfate crystals were dissolved in hot water on a hot plate, and the solution was filtered into a clean beaker and allowed to cool by standing.

Evaluation guide:
(i) Target concept: Purification of impure copper(II) sulfate via hot water recrystallization.
Minimum mechanism: Copper(II) sulfate must be soluble in hot water but less soluble upon cooling; impurities must include at least one component insoluble in hot water to be removed by hot filtration; solution must remain saturated but uncrystallized during cooling phase.
(ii)Storyline: [Phase 1: Setup] Blue granular crystals are present in a beaker placed atop an active hot plate with visible thermal emission. [Phase 2: Dissolution] Crystals visibly reduce in quantity and vanish entirely into clear blue solution as heat is applied. [Phase 3: Filtration] Hot blue solution is poured steadily through a funnel containing white filter paper into a second clean beaker; residue remains trapped on filter paper. [Phase 4: Standing] Final beaker sits motionless with transparent blue liquid; no crystallization, bubbling, evaporation, or external interference occurs. All phases occur from fixed frontal laboratory viewpoint with consistent lighting, no cuts or camera repositioning, and all objects remain fully visible and spatially coherent.

Manual:
Experimental Procedure
1. Blue impure copper(II) sulfate crystals are placed in a beaker with hot water on a hot plate.
2. Crystals fully dissolve upon heating.
3. Hot solution is filtered through filter paper into a clean beaker.
4. Filtered solution stands undisturbed to cool.
Observation of Experimental Phenomena
- Blue crystals disappear completely in hot water.
- Filtrate is transparent blue liquid; insoluble residue remains on filter paper.
- No crystallization occurs in the clean beaker during the brief standing period shown.
Summary of Experimental Principles
This clip captures the hot-dissolution and hot-filtration stages of purifying copper(II) sulfate by recrystallization: heating raises copper(II) sulfate's solubility so the impure crystals dissolve completely, and passing the hot solution through filter paper removes solid impurities that do not dissolve in water. The short standing period shown at the end is neither long nor cool enough for crystals to visibly reform — full recrystallization by cooling proceeds on a slower timescale than this clip covers, so the filtrate stays a clear, saturated blue solution throughout what is shown.

Prompt Grounding rubric:
level_1: None of the four required elements appear: there are no blue impure copper(II) sulfate crystals, no hot plate, no funnel-and-filter-paper assembly, and no clean receiving beaker shown in any recognizable arrangement.
level_2: One or two of the four required elements appear (for example a beaker or a hot plate on its own), but the dissolve-then-filter sequence is never attempted: no crystals are shown entering hot water, no liquid is shown passing through a filter, and no beaker is left standing afterward.
level_3: All four elements appear (blue impure crystals, a hot plate, a funnel fitted with filter paper, and a clean receiving beaker), and at least two of the three required actions (crystals entering the hot water, hot solution poured through the filter, the filled beaker left standing) are shown, but one action is missing or appears out of order, such as the beaker already looking full before any pour is shown.
level_4: All four elements appear in their correct roles, and all three actions (dissolving on the hot plate, filtering the hot solution into the clean beaker, and leaving that beaker undisturbed) occur in the correct order, with only a minor setup flaw remaining, such as the filter paper being hard to make out inside the funnel or the hot plate's heating element not looking active while dissolution happens.
level_5: The blue crystals are visibly granular and irregular in shape, the hot plate's heating element is glowing or visibly giving off steam to show it's active, and the filtration setup clearly shows the funnel, white filter paper, its stem, and clear filtrate entering the beaker (all fully unambiguous), and the three actions run in strict, uninterrupted order (crystals fully entering the hot water, filtrate passing through the filter into the clean beaker, and the beaker then sitting untouched), with no swapped objects, no repositioning of the apparatus between steps, and no extra handling of the beaker after filtration ends.

Scientific and Causal Correctness rubric:
level_1: The crystals shown are white, gray, or colorless rather than blue, or the solution is colorless or yellow instead of blue; no dissolution is shown despite the heating; the poured liquid still contains visible undissolved solid or cloudy particulate matter; the standing beaker shows crystals forming or the liquid boiling instead of sitting quietly.
level_2: The crystals are blue but visibly fail to dissolve even after heating; or the blue solution passes through the filter leaving no residue behind on the paper; or the standing beaker shows crystals already forming, or vapor still rising, in a way that doesn't fit a solution that has stopped being heated.
level_3: The blue crystals visibly shrink and disappear in the hot water, the filtrate is a clear blue liquid, and the filter paper retains a visible residue, and the standing beaker shows no crystal formation during the clip, but one causal link is weak, such as the crystals dissolving with no visible heat source, or the impure starting material leaving no matching residue on the paper.
level_4: The blue crystals dissolve completely in the heated water with nothing left undissolved; filtration yields a clear blue filtrate and leaves a visible insoluble residue on the paper; the standing beaker holds only clear, undisturbed blue liquid with no crystals, bubbles, or visible evaporation, but a minor mismatch remains, such as the residue's color or texture not reading as a plausible insoluble impurity, or the filtrate showing a slight haze the filtration doesn't explain.
level_5: The blue crystals dissolve completely as the hot water is applied, consistent with copper(II) sulfate's higher solubility when hot; filtration clearly separates a clear blue filtrate from a visible insoluble residue trapped on the paper; the filtrate then sits in the clean beaker as a calm, clear blue liquid for the rest of the clip with no clouding, film, suspended particles, crystal formation, condensation on the glass, or meniscus distortion, consistent with a solution that stays saturated but hasn't yet cooled long enough to recrystallize.

Spatiotemporal Consistency rubric:
level_1: The beaker appears already full with no pour ever shown, or crystals appear inside the beaker without being carried there, the funnel or beaker changes size or shape between shots, the filter paper appears to tear or rip during the pour and then looks fully intact again with no repair shown, or the scene jumps from bright to dark lighting within the same sequence.
level_2: One clear break in continuity stands out: for example the hot plate looks like it's glowing before the crystals are shown dissolving, the filter paper switches from empty to full of residue with no flow shown in between, or the beaker's orientation changes between two shots with no camera movement to explain it.
level_3: The hot plate stays under the beaker, the funnel stays aligned above the receiving beaker, and the crystals stay in their original container until poured, with continuous motion throughout (no jump in the pour, no flicker in the rising liquid level), but one small hiccup occurs, such as a hand briefly blocking the funnel stem during the pour, or a single stray flash of light on the glass that doesn't happen again.
level_4: Nothing is substituted, nothing changes shape, no lighting jump occurs, and no motion stutters: the crystals move continuously into the hot water, the filtrate flows continuously through the funnel with the liquid level steadily rising in the beaker, and the beaker stays still with a matching shadow beneath it, but one incidental visual detail remains, such as motion blur on a moving hand that doesn't obscure any of the apparatus, or a stray speck of dust drifting across the shot.
level_5: The hot plate, funnel, filter paper, and beaker stay in the same positions throughout; every motion (the crystals settling into the water, the liquid pouring through the funnel, the filtrate rising in the beaker) is smooth and physically continuous; the hot plate's glow, the funnel's shadow, and the beaker's reflection all stay the same brightness and angle from the first frame to the last; and the camera's viewpoint never cuts or shifts across the whole sequence.