The Properties of Water

Adapted from Biology Junction

WaterA water molecule (H2O), is made up of three atoms.one oxygen and two hydrogen

H

HO

Water is PolarWater is an overall

neutral molecule because it has an equal number of

electrons and protons. The oxygen end “acts”

negativeThe hydrogen end

“acts” positiveThis is why water is described as POLAR

Interaction Between Water MoleculesThe negative oxygen end of one water molecule is attracted to the positive

hydrogen end of another water molecule.

This is why water molecules are attracted to each other.

This is called COHESION.

Cohesion results in SURFACE TENSION-a measure of the strength of water’s surface

Produces a surface film on water that allows insects to walk on the surface of water.

In summary…A water molecule has a positive and negative end (polar), so… water molecules are attracted to water molecules (cohesion) and… this creates surface tension.

Jesus Christ Lizard

Water molecules will make bonds with other surfaces such as glass, soil, plant tissues, and cotton.

Adhesion is the attraction between two different substances.

Adhesion causes Capillary ActionCapillary Action occurs when

water molecules “tow” each other along when in a thin tube.Transpiration is a form of capillary action where plants and trees remove water from the soil, and paper towels soak up water.

In summary…Water molecules have the ability to “climb” structures (adhesion) and this can result in capillary action.

Adhesion also causes water to…

Hold onto plant leaves (the

droplets form due to cohesion)

Attach to a silken spider

web

Meniscus

Turgor Pressure

Celery

Turgor pressure is the pressure that happens when the water located inside the cells begins to expand, pushing on the cell membranes or walls.Turgor pressure is important to the plant cells because it is what gives them the rigidness to stand straight and continue normal cellular functions. If a plant is not able to access enough water to maintain the turgid state then it will begin to wilt, which interferes with function.

Water is called the UNIVERSAL SOLVENTMore substances dissolve in water than in

any other chemical.This is also caused by water’s polarity. The

positive part of an ionic compound is attracted to the oxygen side of a water molecule, and the the negative part of an ionic compound is attracted to

the hydrogen side.

Water is called the UNIVERSAL SOLVENT

Water is the solvent for biochemical

processes.  Hemoglobin,

carbonates, various proteins, and many other molecules in the body use water

as a solvent. 

Water has High Heat Capacity

Specific Heat Capacity is the amount of heat needed to raise or lower 1g of a substance 1°C

Water resists temperature change, both for heating and cooling.

This allows water to act as a buffer for body temperature.

Water is Less Dense as a Solid

Ice is less dense as a solid than as a liquid.

Frozen water (ice) floats on liquid water.

Frozen water forms a crystal-like lattice where molecules are set at

fixed distances.

Water is Less Dense as a Solid

Which is ice and which is water?

Water is Less Dense as a Solid

Water Ice

This is important for organisms that live underwater. If frozen water sunk, small bodies of water would be more likely to freeze completely in the winter, which would be bad for all

the organisms living there. A layer of ice effectively insulates the underlying water, allowing many aquatic organisms to

survive through the winter.

Homeostasisthe ability to maintain a steady state

despite changing conditions

Water is important to thisprocess because:-Water is a good insulator-Water resists temperature change-Water is a universal solvent -Ice protects against temperature extremes (insulates frozen lakes)

Human Tissue % Water

Blood 83.0

Heart 79.2

Muscle 75.6

Brain 74.8

Skin 72.0

Bone 22.0