Ch. 14- Water

Question 1

why is water a liquid on Earth/at room temperature instead of a gas?

Answer 1

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

Question 2

why is solid water less dense than liquid water?

Answer 2

(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

Question 3

specific gravity

Answer 3

the density of a substance compared with water

Question 4

what’s the density of liquid water?

Answer 4

close to 1.00 g/cm3

Question 5

at what temperature range do water molecules expand?

Answer 5

0-4 degrees celcius

Question 6

pros & cons of water expanding during the freezing process

Answer 6

• 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

Question 7

explain how water dissolves different substances

Answer 7

• 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

Question 8

specific heat capacity (specific heat)

Answer 8

the amount of heat required to raise the temperature of 1 g of a substance by 1 °C

Question 9

what is the specific heat of water?

Answer 9

• 1.00 cal/g degrees C

- 4.184 J/g K

Question 10

how can we calculate the amount of heat absorbed or released by a substance?

Answer 10

heat absorbed/released = mass x specific heat capacity x change in temperature (triangle T symbol)

PRACTICE THIS EQUATION IN 14.1!!!!!!!!!

Question 11

heat of vaporization

Answer 11

the amount of heat needed (in kJ/mol or kcal/mol) to convert one mole of a substance from liquid to gas

Question 12

whats water’s heat of vaporization?

Answer 12

40.8 kJ/mol

Question 13

why is water’s heat of vaporization essential to human life & Earth?

Answer 13

• 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

Question 14

what’s a “normal pH” for ocean water?

Answer 14

8.0

Question 15

explain acidification of ocean water & why it’s important

Answer 15

• acid rain & CO2 in the atmosphere acidifies ocean water, forming carbonic acid
• carbonic acid is killing fauna living in the oceans

Question 16

how can we neutralize acidic water?

Answer 16

with the presence of limestone (CaCO3)

Question 17

natural contaminants in Earth’s water

Answer 17

• excessive CO2 in atmosphere
• lightening
• dust in the air

Question 18

dissolved oxygen

Answer 18

oxygen dissolved in water; provides a measure of the water’s ability to support fish and other aquatic life

Question 19

biochemical oxygen demand (BOD)

Answer 19

the quantity of oxygen required by microorganisms to remove organic matter from water

Question 20

eutrophication

Answer 20

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

Question 21

dead zone

Answer 21

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

Question 22

anaerobic decay

Answer 22

the process of anaerobic (not using oxygen) bacteria in bodies of water depleted of oxygen reducing organic matter to methane and hydrogen sulfide

Question 23

Safe Drinking Water Act

Answer 23

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)

Question 24

groundwater contaminents

Answer 24

• 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

Question 25

how much water does 1 person use per day and for what?

Answer 25

~400 L/person (200-600 L/person)

• 7 L for drinking & cooking
• remainder for personal hygiene, laundry/dishwashing, watering lawn/garden, car washing

Question 26

major uses of water

Answer 26

• paper production
• vehicle production
• agriculture

Question 27

use of water in the U.S.

Answer 27

• coolant for electric power plants (48%)
• irrigation (34%)
• public water supplies (11%)
• industrial (5%)
• misc. (2%)

Question 28

flocculent

Answer 28

a substance that causes particles to clump together

Question 29

water purification process

Answer 29

1. water is placed in a settling basin
2. there, it is treated with slaked lime (calcium hydroxide) & a flocculent (such as aluminum sulfate)
3. these materials react to form a gelatinous mass of aluminum hydroxide that carries dirt particles & bacteria to the bottom of the settling tank
4. water is then filtered through sand, gravel, and sometimes activated charcoal
5. filtered water is treated by aeration
6. chlorine is added to kill any remaining bacteria (sometimes ozone is used in addition to/instead of chlorine)

Question 30

primary sewage treatment

Answer 30

treatment of wastewater in a holding pond to allow some of the sewage solids to settle out as sludge

Question 31

secondary sewage treatment

Answer 31

passing effluent from primary sewage treatment through gravel & sand filters, and aerating the water

Question 32

activated sludge method

Answer 32

secondary sewage treatment technique in which sewage is aerated and some sludge is recycled

Question 33

advanced (tertiary) treatment

Answer 33

sewage treatment designed to remove phosphates, nitrates, other soluble impurities, metal compounds, and other contaminants remaining after secondary treatment

Question 34

activated charcoal filtration

Answer 34

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

Question 35

reverse osmosis

Answer 35

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

Question 36

phytoremediation

Answer 36

a method of water and soil treatment that uses plants having an affinity for metal ions and other contaminants to remove those contaminants