• Question: Do you know what the quality is about water that can make it run uphill and not just downhilll? Has to do that to get up that stem.

    Asked by merlindavid98 to Aggelos, Andrew, Eileen, Naomi, Shane on 15 Nov 2012.
    • Photo: Shane Bergin

      Shane Bergin answered on 15 Nov 2012:

      I think you’re talking about capillary action. This is where water can move up through a narrow pipe (very narrow). it’s due to the surface tension of water being very high (water is a very sticky liquid – you can see pond skatters sitting on top of it for instance) and the forces between the water and the glass tube. the reason water can do this more than most liquids is because water molecules really like to stay close to their neighbours (the hydrogens in one water molecule are attracted to the oxygen atom of a neighbouring water molecule – therefore it takes lots of energy to pull them apart – or to break the surface of the liquid)

    • Photo: Aggelos Zacharopoulos

      Aggelos Zacharopoulos answered on 15 Nov 2012:

      @merlindavid98
      capillary action is what comes to mind when reading your question. But it takes place when water is placed inside narrow tubes as Shane explains above.

    • Photo: Andrew Jackson

      Andrew Jackson answered on 15 Nov 2012:

      Trees are really good at using capillary action to draw water up to their top leaves. They don’t have hearts to pump water like giraffes can pump the blood up their long necks. The physics behind this means there is a maximum heights or trees as if they were any taller, capillary cation alone couldn’t lift the water and the leaves would die.

    • Photo: Eileen Diskin

      Eileen Diskin answered on 18 Nov 2012:

      The others are right, its the capillary action that does it. There are some cool experiments you can do, by putting a flower into a glass of water with food colouring in it. This helps you track how quickly and where the water is going through the plant!

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