Chapter 3- Water and Life

what is a polar molecule?

a molecule where the overall charge is unevenly distributed

what shape is a water molecule?

v-shape

what is in a water molecule

one oxygen and two hydrogens

what is the charge on each hydrogen

slightly positive

what is the charge on the oxygen

slightly negative

what kind of bonds hold the hydrogen and oxygen together in a water molecule?

polar covalent, the electrons spend more time closer to the oxygen

properties of water

high surface tension, cohesion and adhesion, high specific heat (heat capacity), high heat of vaporization, ice floats on water, solvent of life

cohesion

hydrogen bonding between like molecules (water on water)

adhesion

hydrogen bonding between unlike molecules (water on others)

transpiration

the movement of water throughout a plant due to cohesion and adhesion.

surface tension

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

what happens with water because of high surface tension?

permits a container to be filled above its rim with water, permits bugs to walk on water

heat capacity/high specific heat

the amount of heat energy required to raise the temperature of a substance by 1 degree Celsius

why does water have high heat capacity

much of the heat energy that is trying to heat it up is being used to break the waters hydrogen bonds

how does high heat capacity help water

large bodies of water can absorb the heat of the sun and store it while barely warming up

high heat of vaporization

the quantity of heat a liquid must absorb for one gram of it to be converted from a liquid to gaseous state

heat of vaporization in water

it takes a lot of heat energy for water to vaporize

how does high heat of vaporization effect water

evaporative cooling occurs because the molecules with the most heat are most likely to leave as gas. this process keeps the earth and body cool.

solid water is ____ dense than liquid water

less

how is ice floating on water beneficial

ice can act as a layer of insulation for the water below, meaning life can exist under that layer

why is water the solvent of life

water can be used to dissolve both polar substances and ionic substances.

solution

a liquid that is a completely homogenous mixture of two or more substances

solvent

dissolving agent

solute

substance being dissolved

what leads to the formation of acids and bases

the dissociation of water molecules

what is an acid

a substance that increases the hydrogen ion concentration of a solution

what is a base

a substance that decreases the hydrogen ion concentration of a solution

what is the pH scale

measure of acidity or alkalinity

what is the neutral pH

pH 7

anything ____ than 7 is an acid

less

anything _______ than 7 is a base

greater

what is a buffer

a substance that minimizes changes in the concentration of H+ and -OH in a solution

what do buffers do

prevent large changes in pH

how do buffers work

they accept H+ ions when the pH drops and donate H+ ions when the pH increases