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Secondary III • 1yr.

How can we tell the order in which substances float on top of each other (in what order they overlap)?

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Explanations (1)

  • Explanation from Alloprof

    Explanation from Alloprof

    This Explanation was submitted by a member of the Alloprof team.

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    Team Alloprof • 1yr.

    Thank you for your question!

    Substances float on top of each other according to their density. Indeed, substances with greater densities will eventually sink to the bottom. On the other hand, substances with smaller densities will eventually float to the surface in order of their densities.

    The phenomenon of superposition is noticeable only with liquids (which may contain some solids) and gases. In fact, superposition is more frequent in liquids as particles in these slides are more easily on top of one another making substances harder to mix. 

    The gases have more difficulty separating because of the turbulence. For example, in the atmosphere, the air remains mixed because of winds and drafts.

    In the same manner of thinking, the particles of the different solid substances do not mix easily making it more difficult to layer in solids.

    Some examples of layering are the separation of the dressing (which is why it must be stirred to prevent the layers from re-forming), the floating of oil on the water, and the fact that humans sink in water (unless they swim, of course). The different objects involved in these examples all have different densities and separate along a density gradient.

     Do not hesitate if you have other questions!