Ch. 14- Water Flashcards
why is water a liquid on Earth/at room temperature instead of a gas?
due to the molecules’ bent shape, strong hydrogen bonds are formed between the molecules, resulting in a much higher boiling point than most molecules that are less than 50 amu in mass typically exhibit
why is solid water less dense than liquid water?
(when water freezes) due to their bent shape and hydrogen bonds, water molecules form an ordered structure of repeating hexagons with empty space in the center of these hexagons, resulting in less density
specific gravity
the density of a substance compared with water
what’s the density of liquid water?
close to 1.00 g/cm3
at what temperature range do water molecules expand?
0-4 degrees celcius
pros & cons of water expanding during the freezing process
- PRO: ice formed in lakes/rivers/oceans/etc. floats on the liquid beneath it, which preserves life in that water; if frozen water sank to the bottom, the entire body of water would eventually freeze, killing all life within that body of water
- CON: our bodies are made of mostly water, so when it freezes in our body, it will expand, breaking/damaging tissue; frostbite can literally kill us, or parts of our bodies
explain how water dissolves different substances
- water repels nonpolar liquids & cannot dissolve nonpolar substances consisting of “infinite” covalent bonding
- water dissolves many other substances by pulling the molecules apart with hydrogen bonding
specific heat capacity (specific heat)
the amount of heat required to raise the temperature of 1 g of a substance by 1 °C
what is the specific heat of water?
- 1.00 cal/g degrees C
- 4.184 J/g K
how can we calculate the amount of heat absorbed or released by a substance?
heat absorbed/released = mass x specific heat capacity x change in temperature (triangle T symbol)
PRACTICE THIS EQUATION IN 14.1!!!!!!!!!
heat of vaporization
the amount of heat needed (in kJ/mol or kcal/mol) to convert one mole of a substance from liquid to gas
whats water’s heat of vaporization?
40.8 kJ/mol
why is water’s heat of vaporization essential to human life & Earth?
- high amounts of heat from the sun are controlled by bodies of water on our planet due to water trapping heat & vaporizing
- high amounts of body heat are trapped & released by water vapor in our bodies, controlling the temperature of the human body
what’s a “normal pH” for ocean water?
8.0
explain acidification of ocean water & why it’s important
- acid rain & CO2 in the atmosphere acidifies ocean water, forming carbonic acid
- carbonic acid is killing fauna living in the oceans
how can we neutralize acidic water?
with the presence of limestone (CaCO3)
natural contaminants in Earth’s water
- excessive CO2 in atmosphere
- lightening
- dust in the air
dissolved oxygen
oxygen dissolved in water; provides a measure of the water’s ability to support fish and other aquatic life
biochemical oxygen demand (BOD)
the quantity of oxygen required by microorganisms to remove organic matter from water
eutrophication
the process by which growth of algae in a body of water is greatly accelerated, usually by phosphates, resulting in depleted oxygen and destruction of that body of water for fish and recreation
dead zone
a region, usually in a large body of water, that does not support fish or other aquatic life because of excess algae and phosphates in the water
anaerobic decay
the process of anaerobic (not using oxygen) bacteria in bodies of water depleted of oxygen reducing organic matter to methane and hydrogen sulfide
Safe Drinking Water Act
states that the EPA has the power to set, monitor, and enforce national health-based standards for a variety of contaminants in municipal water supplies (passed in 1974)
groundwater contaminents
- arsenic
- barium
- copper
- cyanide ion
- fluoride ion
- lead
- nitrate ion
- mercury
- atrazine
- benzene
- p-dichlorobenzene
- dichloromethane
- heptachlor
- lindane
- toluene
- trichloroethylene
- petroleum from leaking storage tanks
how much water does 1 person use per day and for what?
~400 L/person (200-600 L/person)
- 7 L for drinking & cooking
- remainder for personal hygiene, laundry/dishwashing, watering lawn/garden, car washing
major uses of water
- paper production
- vehicle production
- agriculture
use of water in the U.S.
- coolant for electric power plants (48%)
- irrigation (34%)
- public water supplies (11%)
- industrial (5%)
- misc. (2%)
flocculent
a substance that causes particles to clump together
water purification process
- water is placed in a settling basin
- there, it is treated with slaked lime (calcium hydroxide) & a flocculent (such as aluminum sulfate)
- these materials react to form a gelatinous mass of aluminum hydroxide that carries dirt particles & bacteria to the bottom of the settling tank
- water is then filtered through sand, gravel, and sometimes activated charcoal
- filtered water is treated by aeration
- chlorine is added to kill any remaining bacteria (sometimes ozone is used in addition to/instead of chlorine)
primary sewage treatment
treatment of wastewater in a holding pond to allow some of the sewage solids to settle out as sludge
secondary sewage treatment
passing effluent from primary sewage treatment through gravel & sand filters, and aerating the water
activated sludge method
secondary sewage treatment technique in which sewage is aerated and some sludge is recycled
advanced (tertiary) treatment
sewage treatment designed to remove phosphates, nitrates, other soluble impurities, metal compounds, and other contaminants remaining after secondary treatment
activated charcoal filtration
water is passed through small particles of charcoal that absorb (hard to remove) organic molecules from water; after some time, the charcoal becomes saturated & ineffective–can be regenerated by heating it
reverse osmosis
a method of pressure filtration through a semipermeable membrane, leaving contaminants behind; water is forced to flow from a region of high solute concentration to a region of low solute concentration
phytoremediation
a method of water and soil treatment that uses plants having an affinity for metal ions and other contaminants to remove those contaminants
