AP Bio 1.1: Structure of Water and Hydrogen Bonding

what kind of bond does water have?

polar covalent

What is a covalent bond?

A chemical bond formed when two or atoms share electrons.

Why does water have a polar covalent bond?

oxygen is slightly more electronegative (it wants more electrons) so there is an unequal sharing of electrons between the hydrogen and the oxygen

hydrogen bond

a wee bond interaction between the negative and positive regions of two separate molecules

what molecules have to be bonded with hydrogen to create a hydrogen bond?

N,O,F

cohesion

hydrogen bond between two of the same water molecules

adhesion

hydrogen bond between water and one other molecule

surface tension

measure of how difficult it is to stretch or break a bond; result of increased hydrogen bonding forces between water molecules and the surface

what is an example of surface tension?

water on a penny

how does surface tension help plants?

plants rest on top of water for sunlight

what causes water to have a high solvency?

water adhesive property

why does water make such a good solvent?

it is highly electronegative; when a polar molecule is added to water, the slightly positive atom is attracted to the oxygen (slightly negative) and the slightly negative atom is attracted to hydrogen (slightly positive)

what unique hydrogen bond interaction comes from water's cohesive property?

ice can melt on water because it is less dense (helps fish live underneath ice)

Why does water have a high specific heat?

its cohesive property allows the water to absorb a lot of energy before changing states (high heat capacity)

what property of water comes from its cohesive and adhesive properties?

capillary action (think of water going up a straw)

how does capillary action help plants?

they absorb water through their roots

What property of water explains how sweat is a cooling mechanism to maintain body temperature?

evaporative cooling; when water heats up, the fastest molecules escape leaving behind the slower ones (due to their high kinetic energy)

what defines whether or not a substance is an acid?

it has a lot of hydrogen ions

what defines whether or not a substance is an base?

it has a lot of hydroxide ions

pH range for acid

0-6

pH range for base

8-14