Trees send water through their trunks and out their leaves. Fill two cups with the same amount of water, mark the water levels, and tape paper covers over the cups' tops. Take two twigs, removing the leaves from one. Place one twig in each cup, poking the stems through the covers. Wrap a plastic bag around a few leaves to catch the moisture.
Water comes up through the tree's trunk and out to the leaves.
Tie a small plastic bag over the needles of a conifer. Do the same for a broadleaf tree. Check the bags after a few hours and observe the amount of moisture in each bag. Take a trip to a lumberyard. Collect various wood samples, including a piece of redwood.