Chapter 3 Flashcards
How much of Earth’s surface is covered in water?
3/4s
What is water’s molecular shape and why?
wide V, because oxygen is more electronegative than hydrogen, causing polar covalent bonds = polar molecule
charges of oxygen and hydrogen?
oxygen= slightly neg hydrogens = slightly pos
properties of water due to:
attractions –> hydrogen bonds
____ _____ bonds in water molecules result in hydrogen bonding.
polar covalent
four key properties of water
cohesive behavior
ability to moderate temperature
expansion upon freezing
versatility as a solvent
cohesion
collective hydrogen bonds that hold substance together
contributes to transport of water and dissolved nutrients against gravity in plants (eg. hydrogen bonds cause water molecules leaving veins of leaf to tug on molecules further down)
adhesion
clinging of one substance to another
helps counter downward pull of gravity of water to molecules of cell walls
surface tension
measure of how difficult i tis to stretch/break the surface of a liquid
hydrogen-bonds between water molecules give it a high surface tension
How does water moderate temperature?
It absorbs heat from warmer air and releases stored heat to colder air
Can absorb relatively large amount of heat with only a slight change to its own temp
kinetic energy
energy of motion
faster a molecule = greater KE
thermal energy
related to temperature; KE associated w/ random movement of atoms/molecules
temperature
measure of energy that represents the average KE of the molecules in a body of matter, regardless of volume
total thermal energy
depends on matters’ volume
when two objects w/ different temperatures are brought together:
thermal energy passes form waker to cooler object until the two are the same temperature
heat
thermal energy in transfer from one body of matter to another
calorie (cal)
unit of heat; amount of heat it takes to raise the temperature of 1 g of water by 1 C.
kilocalorie (kcal)
1k calories; quantity of heat required to raise temperature of 1 kg of water by 1 C
joule (J)
0.239 cal; 4.184 J = 1 cal
specific heat
amount of heat the trust be absorbed/lost for 1 g of that substance to change its temperature by 1 C
water’s specific heat
1 cal/g x C
Why is water’s specific heat so high?
hydrogen bonds must be broken 1st before water molecules can begin moving faster
Why is water’s specific heat so important?
large body of water can absorb/store huge amount of heat while warming only a few degrees
at night/winter, gradually cooling air can warm the air; moderates temperatures in coastal areas
stabilizes ocean temperatures, creating favorable enviro
keeps temperature fluctuations within limits that permit life
evaporation/vaporization
transformation from liquid to gas
heat of vaporization
quantity of heat a liquid must absorb for 1 g to be converted from liquid to gas
water’s heat of vaporization and benefits
580 cal of heat needed
results from strength of hydrogen bonds
helps moderate Earth’s climate (moist air forms air)
accounts for severity of steam burns