The causitive agent of the cohesion-tension model of xylem transport is transpiration. During the process of transpiration, water vapor is lost from the stomata of the leaf. To replace this water, water from adjacent cells is withdrawn. The water molecules stick together due to cohesion and are transported upwards through the stem in the form of a stream.<span />
Metals conduct electricity and heat, indicating that the electrons are free to move. Metals are malleable, showing that atoms are not in fixed positions but can remain bonded even though they change their positions. In metallic bonding, atoms donate electrons to a pool and all the atoms share in the pool. No compounds are formed, but the atoms are bonded into a network.
