✎ Separating molecules

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ANSWER

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1. He is separating small and big molecules.
2. All the big gravel will left in the screen.
3. Chromatography
4. Yes

Explanation:

Chromatography is a process for separating components of a mixture. The different components of the mixture travel through the stationary phase at different speeds, causing them to separate from one another.

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Answer:

screening sand to become fine sand