General Biology I - Water

Water makes life

possible on earth

Water deals with

structure and interactions with supporting materials

2 H atoms are held together by

a covalent bond

Liquid H20 is a

V-shaped molecule

O

is more electronegatice so electrions shared covalently spend more time near O atom than 2 H atoms, O atom gets a partial negative charge

Hydrogen bonds occur

when S+ H atom of one molecule

Hydrogen bonds are individual and

weak

Properties of water

1. Cohesion and Adhesion

2. Bodt Temp

3. Expand when Freezing

4. Solvent

Cohesive

Specifically associated with water, process where H20 is attracted to H20 through hydrogen bonding

Cohesion makes water

very structured

Adhestion

Clinging of one substance to another

Choestion and Adhesion

Allow water to move against gravity

As H20 evaporates

it pulls on the H20 molecules the connected molecules pull it lower

Adhesion

H20 clings to cell walls of Xylem that carries H20

Surface tension

How hard it is to stretch or break surgace or liquid

Species are

Bound to water below and not attached to air above it

Moderation of Temperature

Specific Heat & Heat of Vaporization

High specific heat

1 cal/g per degrees Celsius

High heat of vaporization

580 cal at 25 degrees C

Specific heat

Amount of heat that must be absorbed or lost for one gram of a substance to change its temperature or to measure the extent of temperature change resistance

Water requires

large amounts of energy to break or form bonds and change its temperature

70-90% of our cells

are H20

H2O

minimizes temperature fluctuation

Heat of Vaporization

Amount of a heat must absorb for 1 gram to be converted to a gas

Evaporative Cooling

As a liquid evaporates, the remaining surface is cooler

Examples of evaporative ooling

Sweating, panting, bathing

Water is unique

when frozen because it is less dense as a solid than a liquid

Water expands as it freezes so

ice floats on liquid water

H2O is pushed apart

when freezing

If ice sank,

water would freeze solid and make life impossible

Ice acts as an

insulator

water is the solution of

2 completely homogenous liquid made of 2 or more substances

Solvent

Substance that promotes dissolving

Solute

Substance that is dissolved

Aqeous Solution

When water’s solvent is water’s polarity caauses H+ atoms to be attracted to negatively charged aroms

• some atoms are attracted to Na+ atoms

The bonds

shield ions/atoms

Hydrophillic

Water permeable, has affinity for water and can bind to water and or dissolve polar and ionic substances

Hydrophobic

Those that do not have an affinity for H20 and do not dissolve in it

Hydropphobic examples

Non-polar & non-ionic

Dissociation of wayer

Sometimes when 2 H2o molecules break amart, a hydrogen atom in 1 molecule shifts or moves to another, it breaks the hydrgoen bond

When H+ gets transfered to other H20 molecule,

it will leave an electron behind

Hydronium-recieved

H+W

When you have OH-,

there are equal amounts

10^-7M

Scale

pH scale

measure how acific or basic a solution it (negative loagrithm of hydrogen ion concentration pH = -log

In pure H2O when H breaks apart

10^-7 of H+

Difference of 10x between 2 things

Neutral amount of H+ is equal to

amount of OH-

Acids

Donate protons, remove OH- from a solution and both increase H+ in a solution

Bases

Remove protons, donate OH- in a solution and both increase OH- in a solution

Buffers are

Substances in bodies that maintain pH

Donate H ore remove OH if

out cells need to become acidic (weak acid)

Donate OH- or remove H+ if our cells need to become more basic to reach ideal

Ph (cooresponding base)