AP Biology Unit 1.1

water

-polar molecule

-polar colvalent bonds

-oxygen end is partial negative and the hydrogens have a partially positive end

-cohesive

-tend to move a lot. Hydrogen bonds form, break and re-form with great frequency. Solid has the strongest IMF and is less dense.

polar covalent bonds

-opposite ends of the molecule have opposite charges

-electrons shared unequally (larger difference in EN)

Chemical Structure of Water- Polarity

Since Oxygen is more electronegative compared to Hydrogen, there is an unequal sharing of electrons between O and H. This covalent bonding can result in polarity when there are differences in atomic electro-negativities. Consequently, a water molecule has polarity.

nonpolar covalent bond

a covalent bond in which electrons are evenly shared between atoms. (small difference in EN)

hydrogen bonding

the strongest of the intermolecular forces. The slightly positive charge of the H of one molecule is strongly attracted to the slightly negative charge on the F, O or N of another molecule. 1 water molecule can attract 4 other water molecules which then form 4 hydrogen bonds. (S-L-G).

Hydrogen bonding is a weak bond interaction (IMF) between the negative and positive regions of 2 separate molecules. Water can form hydrogen bonds (IMF) with other water molecules or other charged molecules. When 2 of the same molecules form hydrogen bonds with each other, it results in cohesion, Additionally, when 2 different molecules form hydrogen bonds it is called adhesion.

emergent properties of water

Refer to hydrogen bonding and mention polar molecules.

cohesion

-Water molecules joined to other water molecules

-H bonding between H2O creates it (sticky)

-allows for the movement of water against gravity

-high surface tension: an elastic sheet like property as a result of IMF.

-water moves up a tree by transpiration: the movement of water molecules through the xylem and their evaporation through the stomata in plants.

adhesion

-H2O molecules form H bonds with other substances. Water moleculed clinging to another surface.

~capillary action

~meniscus

~water climbs up fiber

solvent

-water has a high solvency ability in the liquid state.

-polar water molecules will surround the (+) and (-) ions causing the ions to separate and dissolve

-dissolve solutes and create aqueous solutions

-"like dissolves like"

Chemical characteristics of Water

Chemical characteristics like result from surface tension, cohesive, and adhesive properties.These three properties allow for water to demonstrate additional chemical behaviors known as emergent properties.

-Surface tension is the result of increased hydrogen bonding forces between water molecules at the surface.

-Water's adhesive property gives it a high solvency ability in the liquid state.

-Water's cohesive property allows for unique hydrogen bonding interactions to occur in the solid state, making ice (solid) less dense than liquid water. Also, water's cohesive property allows it to absorb a lot of thermal energy before changing chemical states, resisting sudden changes in temperature.

-Lastly, capillary action is the result of both adhesive and cohesive properties of water.

Living systems dependent on Water

-Many plants will sit on the surface of water due to surface tension which allows them to gain access to sunlight and perform photosynthesis.

-Moreover, organisms must obtain key nutrients from their environment. Since living things are made up of about 70% water dissolved materials in the water allow for easy access by cells.

-Aquatic organisms are still able to live in water with freezing climates because the water will freeze on the surface leaving liquid water underneath for those organisms to still thrive. Many aquatic organisms like fish will depend on water's high specific heat property in order to maintain appropriate temperature regulation of their bodies. -Due to capillary action, plants can access water from the soil.

hydrophilic

-some molecules have an affinity for water (love water)

-water soluble

-polar and ionic molecules, some proteins and sugars

-ex: cotton, cellulose, paper

hydrophobic

-some substances do not have an affinity for water (fear water)

-nonpolar and non ionic substances

-ex: lipids (fat), glycerol, oils

floats

-less dense when it is solid

-forms crystal lattice structure

-important because oceans and lakes do not freeze solid

~insulates water below

~seasonal turnover of lakes

pH scale

based on the concentration of H+ and OH- ions. (1-14) Strong bases are very high pH and strong acids have very low pH

(H+): is a single proton with a +1 charge

(OH-): has a -1 charge

Water molecules dissociates into its ions. H+ and OH- and with an extra H+ will form a hydronium ion.

specific heat

-the amount of heat that must be absorbed or lost for 1g to change its temperature by 1C

-water had high _____ due to H bonding

-resists change in temp

-moderates temp on earth

evaporative cooling

-organisms use to regulate their temperature

-ex: sweating

-water evaporates through a surface, cooling occurs

Molarity (M)

number of moles of solute dissolved in 1 liter of solution.

acidic

If [H+]>[-OH]

-a substance that increases H+ concentration

-Proton donor

-pH below 7.0

-Higher concentration of H+ than OH-

basic

If [-OH]>[H+]

-a substance that increases OH- concentration

-Proton acceptor

pH above 7.0

-Higher concentration of OH- than H+

pH scale represents:

-how acidic or basic a solution is

-most biological fluids have 6-8

-each unit represents a 10-fold difference in H+ and -OH concentrations

neutral

-If concentration of 2 ions is equal (H+)=(OH-) concentration

Buffers

Minimizes changes in the [H+ ] concentration and [OH- ]

-In the presence of an acid, excess H+ ions are accepted.

-Works by accepting excess H+ ions or donating H+ ions when depleted.

Burning Fossil Fuels and Acidification

Burning fossil fuels releases CO2. About 25% gets absorbed by oceans.

CO2 +H2O➝H2CO3. H2CO3 can then dissociate and the acidity can affect the organisms living in the ocean.

Acidification: Nitrogen and Sulfur oxides react with water in air to form strong acids that fall to Earth with rain or snow damaging life in lakes or streams or plants on land.

carbon

-all life mostly based on this element

-important due to its electron configuration

~able to make 4 stable covalent bonds (tetra valence)

~very versatile

-tetravalence allows them to be strung together in chains

hydrocarbons

-combinations of C and H

-nonpolar

~not soluble in water

~hydrophobic

-stable

-very little attraction between molecules

-gas at room temp

isomers

-molecules with the same molecular formula but different structures

-different chemical properties

-different biological functions

structural isomers

-differ in covalent arrangement of atoms

geometric isomers

-same covalent relationships by different spatial arrangements

functional groups

-substitute other elements for hydrogen

-parts of organic molecules that are involved in chemical reactions

-give organic molecules distinctive properties

-affect reactivity

~make hydrocarbons hydrophilic

~increase solubility in water

macromolecules

-by joining carbon to other elements, we form the basis of life

-smaller organic molecules join together to form larger molecules