|THE MAGIC OF WATER||REEC HOME||Year 2-6 HOME||WATER CONTENTS|
12. Why can water go up a straw?
Water is a "sticky" molecule and likes to stick to other water molecules and also other things such as glass, plastic, soil and cloth.
Dip a paper towel or tissue in water and observe.
Does the water go into the tissue?
If the tissue is held vertically does the water go up the tissue?
What eventually stops the water from going higher (the same reason you fall back down when you jump up)?
Water in the soil enters plant roots and travels up the narrow tubes in the plant to the leaves where it evaporates into the air. When water molecule one evaporates from a leaf, molecule two moves up and pulls molecule three with it which pulls molecule four up and so on.
The raising of water in a narrow tube is called the capillary effect. A capillary is a very narrow tube. This also allows water deep in the soil to come to the surface and explains why ploughing a field, breaking the tube-like spaces in the soil, reduces evaporation from the soil, saving soil moisture.
Next: Why do we use water to flush a toilet?
Riverina Environmental Education Centre