Biology properties of water

chapter 3

Cohesion

tendency of water to stick to itself.

adhesion

tendency of water to stick to other polar substances

polar

uneven distributions of electrons (electrical charge)

• one side is slightly positive

• one side is slightly negative

ice floats

When thermal energy decreases, molecular kinetic energy decreases. The water molecules move less, allowing hydrogen bonds to lock them into a spread-out structure. This causes water to expand, which lowers its density, so ice floats.

Great BIOLOGICAL solvent

water is a great biological solvent because its polar, and its polar molecules form hydrogen shells around ions and polar molecules, allowing them to dissolve.

covalent bonds

electrons are shared

ionic bonds

electrons are transferred (oppositely charged ions)

high specific heat

Because hydrogen bonds absorb thermal energy, water can absorb large amounts of heat without greatly increasing its temperature, which helps moderate the temperature of nearby land.

high heat of vaporization

Water has a high heat of vaporization because a large amount of thermal energy is required to break hydrogen bonds and change water from a liquid to a gas.

evaporative cooling

When water evaporates, it takes heat with it, leaving less thermal energy behind and causing the surface to cool.

ex: sweating

capillary action

Water moves upward against gravity because water sticks to itself (cohesion) and other surfaces (adhesion).

(gravity pulls everything down, in order for water ti go up, it uses cohesion and adhesion to make it happen.) ( to go up the xylem.)

surface tension

the physical property of a liquid that makes its surface act like a stretched elastic skin

solute

substance that gets dissolved

solvent

substance that does the dissolbving

hydrophobic

does not mix or interact with water

heat capacity

how much heat a substance can absorb before its temperature increases.