properties of water lesson

1. Cohesion & adhesion2. Low density solid3. Solubility: a good solvent4. High specific heat capacity5. High heat of vaporization & fusion6. Ionization: determines pH

Cohesion: the clinging of a substance to itself hydrogen bonds between water

molecules holding water togetherAdhesion:

the clinging of one substance to another E.g. Meniscus: hydrogen bonds between

water molecules and the glass of a test tube

A measure of how difficult it is to break the surface of a liquid

Surface tension is one of the results of cohesion in water

Video: A National Geographic video showing how a lizard employs the water property of high surface tension

Water is most dense at 4oC

Ice is less dense than water

Water is the only type of matter which becomes less dense when a solid

Aquatic life When the temperature

of the atmosphere falls below 0oC, the water at the surface gradually freezes to ice

The water under the ice remains at 4oC

Amount of heat energy needed to increase the temperature of a substance by 1oC

Water has a high specific heat capacity: Water is capable of absorbing a lot of

heat without increasing in temperature Demonstration: water balloon

Help organisms maintain constant body temperature

Large bodies of water have moderating effect on nearby land temperature

Heat of vaporization: amount of heat a liquid must absorb to be converted to a gas

Heat of fusion: amount of heat a solid must absorb to be converted to a liquid

Water has high heat of both vaporization and fusion

Relevance: sweat

Hydration shellSome biologically significant

solutes include salts, sugars, proteins, vitamins

Hydration Shells

Many molecules are able to dissolve in water.

Organic matter may be hydrophilic or hydrophobic.

H2O H+ + OH-

ReversiblepH = -log[H+]

Relevance: Organisms are very sensitive to pH changes

Is water an acid or a base?

H2O + H2O H3O+ + OH-

Is water an acid or a base?

H2O + H2O H3O+ + OH-

acid conjugate base

baseconjugate

acid

Acid compounds that will donate a proton

in solution results in a negative charge

Base compounds that will receive a proton

in solution results in a positive charge