To find out what the plant does with the water we give it we put a plastic bag on a sprig of a plant. We used a Ziploc bag and taped over the part where the plant went into the bag so that it was like it was in it's own little personal green house.
Now for the science part of it. A plant looses about 90% of the water it absorbs through it's pores, the stomata and the leaves. A large tree can loose up to 15,000 pounds of water in 12 hours. We felt that when we went to the arboretum a few weeks back. When we walked into the room where all the tropical plants were it was so humid it was hard breath. This loss of water is called transpiration.
I think if we had tried this experiment in the summer when it get hotter in the window we would have seen more condensation.