How capillary action makes water go up…

Even though we usually think of water as running downhill, it can indeed flow upwards using a process called capillary action. This is the very scientific principal that explains how water goes from the soil upwards into the stem of plants. Plants contain many vein like tubes that carry water from the plant’s roots upwards to the plant’s highest leafs via capillary action. Try this experiment to see capillary action in action.

1. Wrap the plastic wrap around the knitting needle and then tape the edges so that you have formed a tube. Remember, the narrower the tube, the more pronounced the capillary effect will be.
2. Once you have taped the plastic wrap, pull out the knitting needle. Make sure that the new plastic tube is not bent and is open at both ends.
3. Now pour a little of the food coloring into a glass half filled with water.
4. Now place your plastic tube into the glass of water.
5. Examine the tube carefully. The dye should climb up the tube above the level of the liquid in the glass.

Now try the same experiment with varying levels of water in the glass. Does this make a difference?

Experiment Supplies

Supplies: Tape, Plastic wrap, Knitting needle, Food dye

Sources: MIT