How do the properties of cohesion and adhesion contribute to water going from roots to leaves against the force of gravity?
Cohesion means that like molecules stick together due to an attraction. The formula for water is H20 and because of its configuration, it can make four hydrogen bonds to other water molecules. That is why water as it drips out of a faucet seems to stretch--the molecules are sticking together. Adhesion occurs when different particles or surfaces cling to eachother. For example if water droplets cover a high surface area on a solid surface, more adhesion will be present. When roots absorb water, capillary action takes place inside the xylem tubes, which are like tiny drinking straws. Inside thin tubes, there will be adhesion between the water molecules and the walls of the tube and there is cohesion between the water molecules causing them to stick together. They will travel up through the xylem tubes by capillary action. This can be seen when one dips the edge of a paper towel into water and the water moves up through the towel against gravity. Transpiration pull occurs as water evaporates out of the stomates in the leaf and this leaves behind space for more water molecules to be pulled upward against the force of gravity.