BIO104 Chapter 2.2-2.3 Covalent bonds, Hydrogen bonds, Molecules, Water

Covalent Bond

Results when atoms share electrons in such a way that each atom has an octet of electrons in outer orbital

Single Covalent Bond

Results from sharing one pair of electrons

Double Covalent Bond

Results from sharing two pairs of electrons

Triple Covalent Bond

Results from sharing three pairs of electrons

Shape of molecules

Three dimensional

Nonpolar

Electrons are shared equally in a _____ covalent bond

Polar

Electrons are shared unequally in a _______ covalent bond

Electronnegativity

The attraction of an atom for electrons in a covalent bond

In a nonpolar covalent bond

Electrons are being shared equally in the atomic nuclei and molecules are considered neutral (stable)

In a polar covalent bond

The sharing between two atoms in unequal (not neutral)

Dotted lines

Represent hydrogen bonds

Hydrogen bond

The attraction between a partially negative (-) oxygen in one molecule and a partially positive (+) hydrogen in another molecule (break easily)

Chemistry of water

Water is polar, water molecules form hydrogen bonds, first cells evolved in water (solid, liquid, gas)

Property of Water

High heat capacity, requires a lot of energy

Calorie

The amount of heat energy needed to raise the temperature of 1 gram of water 1 degree celcius

Homestasis

Maintaining stable internal conditions

Water has a high heat of vaporization

Important to homeostasis

Evaporative Cooling

Too hot=sweat, sweat evaporates leaving you cooler

Water is a solvent

Wide range of substances are able to be dissolved (also polar)

Solution

Contains dissolved substances which are called solutes

Hydrophilic

Attracted to water (water loving), sugars, amino acids

Hydrophobic

Do not attract water, oils (clumping)

Cohesion

Tendency of a molecule of a substance to stick together (ex. water)

Importance of Cohesion

Water links together through hydrogen bonds and creates links

Adhesion

Tendency of a polar molecule such as water to adhere to other polar surfaces (ex. sticks to glass)

Importance of adhesion

Water molecules can bind to polar surfaces

Surface tension

Tension of the surface film of a liquid caused by the attraction of particles in the surface layer by the bulk of the liquid (insects use this to walk on bodies of water)

Downfall of surface tension

When hydrogen bonds break so does surface tension

Ice

Less dense than water

Freezing

Bodies of water freeze from top to bottom

Heat of Fusion

Energy in order to change a solid to a liquid

Insulation

Ice forms on the top of bodies of bodies of water creating…

Dynamic equilibrium

The state that water is in where water molecules dissociate at the same rate at which they are being reformed

Pure water

Amount of hydroxide equals hydrogen (neutral)

Acids

Substances that release hydrogen ions (H) when dissociated with water (ex. Hcl —> H+ +Cl-)

Bases

Substances that either release hydroxide ions (OH-) or take up hydrogen ions (H+) (More hydroxide ions then hydrogen)

PH scale

To reflect the acidity or basicity (alkalinity) of solutions

PH 7

Neutral

PH below 7

acidic

PH above 7

basic

Buffer

Chemical or combination of chemicals that keep PH within normal levels (combining or donating)

Bicarbonate ions

(HCO3-) and carbonic acid (H2CO3) found in human blood buffers the PH to 7.4, essential for regulating blood PH

7.4

Human body tries to maintain this blood PH