Get a white carnation. With help from an adult, very carefully cut the carnation's stem lengthwise, from the bottom up to the flower. Now fill two glasses with water. Use food colouring to colour the water in one of the glasses dark red. Colour the water in the other glass dark blue. Put the glasses right next to each other. Put a half of the carnation stem into each glass. Check the carnation a few hours later. Can you tell that the carnation has been drinking water?