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What are the properties of liquids?

Using a high-pressure water jet.Using a high-pressure water jet.A liquid's molecules can move around more than in solids. This means a liquid can change shape and flow, although, like solids, it still takes up the same volume. Liquids cannot be stretched or cut into pieces in the way that some solids can. A liquid's molecules also cannot be squeezed together. So when a liquid flows through a narrow space such as a pipe, it pushes against the wall of the container. In other words, its pressure is greater.

Water molecules as solid ice (left) and liquid (right)Water molecules as solid ice (left) and liquid (right)


Water striders moving on the water’s surfaceWater striders moving on the water’s surface

Surface tension

The molecules forming the surface of a liquid are bound together in a force called surface tension. It is as if the liquid has a stretchy skin on its surface. This "skin" enables some insects, such as water striders, to move about on the surface of water.



Molasses, a highly viscous liquidMolasses, a highly viscous liquidSome liquids can flow more easily than others. Water, for example, flows more easily than oil. Viscosity, or runniness, is the term used to describe this property. In a runny liquid like water, molecules slide over one another more easily than those of a more viscous liquid like oil. 

Surface tension also explains the formation of water droplets that we see on window panes or twigs, for example. The "skin" of the liquid holds the liquid together in a rounded shape for a time.

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