2: Water Flashcards
most abundant compound in organisms (70% of body weight)
water
molecular geometry of water
bent or V-shaped (nearly tetrahedral arrangement of four electron groups around O)
how many hydrogen bonds can each water molecule make?
4 (2 on oxygen, 1 on each hydrogen)
8 unique properties of water that sustain life on Earth
high cohesion
high adhesion
high surface tension
high specific heat
high heat of vaporization
liquid at room temperature
excellent solvent
hydrophobic exclusion
act of sticking together
cohesion
act of sticking to something (due to ability of water to form H bonds)
adhesion
what component of plant cell walls can form H bonds with water molecules, allowing the latter’s transport?
cellulose (the hydroxyl groups)
measure of the resistance of a substance to increase its surface area due to high cohesion of its molecules
surface tension
2 types of molecules in a sample of water
inner and surface
explain the high surface tension in water
there is formation of stronger bond between surface water molecules as they are pulled inward by a net inward force due to absence of attractive force acting from above and thus preventing them from being stretched or broken
2 importance of high surface tension of water
- allows denser things and animals to float
- formation of water droplets
amount of heat per unit mass required to raise the temperature by 1degree Celsius
specific heat
specific heat of water
2 cal/g-degree Celsius
what happens when temperature of water increases? decreases?
increase in T: water molecules would move faster due to increase in kinetic energy, leading to the breaking of H bonds which absorbs heat
decrease in T: water molecules would move slower due to decrease in KE, causing the formation of H bonds which releases heat
2 importance of moderation of temperature by water
regulate air temperature change near oceans
regulation of internal body temperature
process at which as liquid evaporates, the liquid surface that remains behind cools down
evaporative cooling
what makes evaporative cooling possible
high heat of vaporization of water
amount of heat needed to turn 1 g of liquid into a vapor without a rise in temperature of the liquid
heat of vaporization
heat of vaporization of water
540 cal/g at 25 degrees Celsius (high due to hydrogen bonding)
2 importance of evaporative cooling
sweating
evaporation of water on the surface of leaves
how many hydrogen bonds does water molecules form on ice? on liquid water?
ice: 4 H bonds, stable
liquid water: 3.2 H bonds on average, constant breaking and reformation of H bonds
ice is ____ than water
less dense
why does water readily dissolve other polar compounds and salts?
high dielectric constant
measure of the ability of a solvent to keep opposite charges apart
dielectric constant
