lesson 3- water and life & ph and buffers

cohesion

linking together of like molecules

adhesion

clinging of one substance to another

in a water molecule, the oxygen atom

carries a partial negative charge

in a water molecule, the hydrogen atom

carries a partial positive charge

hydrogen bond

slightly positive hydrogen of one water molecule is attracted to the slightly negative oxygen of a different water molecule

emergent properties of water that are critical for life

• cohesion/adhesion of water molecules

• moderation of temperature by water

• floating of ice on liquid water

• water is an excellent solvent

what does adhesion do?

adhesion of water to cell walls helps counter the downward pull of gravity

what does cohesion do?

contributes to the transport of water and dissolved nutrients against gravity

surface tension

measure of how difficult it is to stretch or break the surface of a liquid

heat

measure of the matter’s total kinetic energy due to the motion of its molecules. depends on the matter’s volume

temperature

measure of heat intensity. represents the average kinetic energy of the molecules

1 calorie equals

amount of heat to raise the temperature of 1g of water by 1 °C

1 kilocalorie equals

amount of heat necessary to raise the temperature of 1kg of water by 1 °C

specific heat

amount of heat that must be absorbed or lost for 1h of a substance to change its temperature by 1°C

why does water have a high specific heat?

hydrogen bonding releases energy when hydrogen bonds are formed

evaporative cooling

keeps organisms cool. when water molecules evaporate, the remaining liquid is cooler as the molecules with the most kinetic energy leave the liquid phase

why is water unusual?

the solid phase of water is less dense than the liquid phase. hydrogen bonds cannot be broken

solution

liquid that is a homogenous mixture of two or more substances

solvent

the dissolving agent of a solution

solute

substance that is dissolved in a solution

solvent explanation

a solute dissolved in a solvent to make a solution

what do water molecules do (solvent)?

form a hydrogen shell as oxygen atoms are attracted to cations and hydrogen atoms are attracted to anions

amino acids

building blocks for proteins

hydration shell

when water interacts with the charged surface of a protein. water is polar

hydrophilic

water loving: salts, charged molecules, and polar molecules that will dissolve in water

hydrophobic

water fearing: oils, non-polar amino acids, and molecules that will not dissolved in water/create hydrogen bonds

creating ions

hydrogen atom participating in a hydrogen bond between 2
water molecules can shift from one molecule to the other

hydroxide ion

ion that shifted in a hydrogen bond and lost one of its proteins

acid

a substance that increases the hydrogen ion (H+) concentration of a solution

base

a substance that reduces the hydrogen ion (H+)
concentration of a solution

log scale

way of compresses the range of H+ and OH- concentrations

difference in log scale

1 unit represents a tenfold different in H+ and OH- concentrations

ph of a solution

negative logarithm= -log[10^-x]

acids…

have a higher [H+]

bases…

have a lower [H+]

buffers

prevent rapid changes in pH when an acid or case is added to a solution/compounds that readily accept or donate H+ ions