GB1- Chapter 3

Water’s four properrties that facilitate environment for life

1. cohesive behavior

2. ability to moderate temperature

3. expansion upon freezing

4. versatility as a solvent

cohesion

hydrogen bonds holding water molecules together

transports water and dissolved nutrients against gravity in plants

results in high surface tension

surface tension

how difficult it is to stretch or break the liquid’s surface

adhesion

attraction between different substances

ex) water and plant cell wall

kinetic energy

energy of motion

thermal energy

kinetic energy associated with random motion of atoms or molecules

temperature

average kinetic energy of the molecules in a body of matter

heat

transfer of thermal energy

calorie (cal)

amount of heat required to raise the temperature 1g water by 1ºC

amount of heat released when 1g of water goes down 1ºC

specific heat

amount of heat that must be absorbed or lost for 1g of substance to change 1ºC

water resists temperature change because of its high specific heat of 1 calorie

heat of vaporization

amount of heat 1g of liquid must absorb to be converted to gas

evaporative cooling

cooling of the surface after evaporation because the molecules with the greatest kinetic energy leave as gas

stabilizes temperature in organisms and bodies of water

ex) sweating

water’s density

water is more dense as liquid than solid

at 0ºC water molcules lock into crystalline lattice- hydrogen bonds keep the molecules far apart = makes ice 10% less denser than water

water’s greatest density is at 4ºC

solution

homogeneous mixture of liquid substances

solvent

dissolving agent

solute

substance that is dissolved

aqueous solution

water is the solvent

hydration shell

water molcules surrounding ionic compound

hydrophilic

affinity for water

“water loving”

hydrophobic

doesn’t have affinity

ex) oil molecules are hydrophobic because of their nonpolar composition

molecular mass

sum of all atom masses in a molecule

molecular mass: 1 mol

Molarity

number of moles of solute per liter of solution

mol/L

number of molecules

1 mole = 6.02 ´ 10²³ molecules

hydrogen ion (H⁺)

leaves electrion behind and becomes a proton

hydroxide ion (OH^–)

lost proton = anion

hydronium ion (H₃O⁺)

extra proton

acid

increases H⁺ concentration in soltuion

lower than 7

base

reduces H⁺concentration in solution

higher than 7

pH

pH = –log [H⁺]

most biological fluids have 6-8 pH

Buffer

substances that minimizes change in concentration’s H⁺ and OH^–

contains weak acid and corresponding base; combines reversibly with H⁺ ions