A substance occupies one half of an open container. The atoms of the substance are closely packed but are still able to slide past each other. What is most likely the phase of the substance?

Closely packed atoms that can slide past one another describe a liquid: liquids keep a fairly definite volume but do not have a fixed shape. Filling one half of an open container is also consistent with a liquid, whereas a gas spreads to fill the entire container and a solid keeps its shape. Therefore, the substance is most likely a liquid.

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