Properties of water

Question 1

what are the basic properties of water?

Answer 1

three states
H2O
polar bond
hydrogen bonds

Question 2

why is water essential for life?

Answer 2

circulates all time in varying states
scarce and valuable
by 2025 more than 1/2 world pop could face water based vulnerability

Question 3

what % of the planet does water make up?

Answer 3

70%

97% is salt, 1% fw

Question 4

what does water do?

Answer 4

Carries minerals and chemicals
Aids dispersal of sediments/seeds
Sculpts landscape
Transparent - aquatic plants can live within the water. Very productive system
Absorbs energy (heat) - solid to gas
Releases energy gas (heat) - solid
Important for buffering planet against temp extremes

Question 5

what are the properties of water because of hydrogen bonds?

Answer 5

Cohesive behaviour - similar molecules attract each other
Resists change in temp
High heat of vaporization
Expands when freezes - less dense
High adhesion
High solubility of chemical compounds in water

Question 6

what does water being a solvent show?

Answer 6

polar

attracts positive and negative ions

Question 7

what is seawater made up of?

Answer 7

ratio of abundant components almost components 
change in salinity by removing/adding pure water 
chloride ions (55%) sodium (31%)

Question 8

what is the heat capacity?

Answer 8

the amount of heat required to change the temp by a given amount
Expressed in joules per K

Question 9

what is specific heat capacity?

Answer 9

heat capacity per unit mass of a body - energy needed to change 1kg by 1C

Question 10

what is heat not the same as?

Answer 10

temperature

Question 11

what is latent heat?

Answer 11

The amount of energy released/absorbed by a substance during a change of state that occurs without changing its temp

Question 12

what is the change in energy with heat?

Answer 12

no change in kinetic energy

Question 13

where does energy come from?

Answer 13

Energy released comes from the potential energy stored in the bonds between the particles

Question 14

what happens when water absorbs/releases heat?

Answer 14

only slight change in its own temp

Question 15

what is the change in temp in the oceans?

Answer 15

large difference between night/day, but little change in oceans

Question 16

why do gases and liquids not mix?

Answer 16

cohesion forces greater than adhesion forces
Intermolecular attractions in every direction (H bond) force is negligible (cancel out)
This not the case on the surface molecules - here net force is downwards as the intermolecular attractions with the air molecules is negligible. Water molecules cohere strongly at surface
The compression resistance of the liquid will limit the downward force and a compressed layer forms at the surface

Question 17

equation for pressure?

Answer 17

p = F/A

Units expressed as kg/A

Question 18

what does water pressure at a given depth depend on?

Answer 18

mass of water above that depth

Question 19

at 1m depth what is the mass of water above?

Answer 19

1 cubic meter

Question 20

what is pressure reported at?

Answer 20

10,000Pa, 1dbar, 0.1bar

Question 21

whats the equation for density?

Answer 21

(p) the mass per unit volume (kg/m^3))

Question 22

what effects density?

Answer 22

temp (biggest effect), salinity and pressure

Question 23

what happens with change in density?

Answer 23

water parcels moving (convection, thermohaline circulation)

Question 24

what’s the density of water like in the med?

Answer 24

little freshwater in, high evaporation rate so salinity much higher and so much denser - sinks when meets atlantic and moves over sea floor

Question 25

what happens to water below 0C?

Answer 25

form hexagonal crystals which cause water to expand

Question 26

what happens to water between 0-4C?

Answer 26

added energy will break some H bonds of long chains and H20 molecules will move up more freely
- Water expands, density decreases

Question 27

what happens above 4C?

Answer 27

more energy breaks H bonds, water moves more freely, water expands, density decreases

Question 28

what happens to water between 0-4C with high salinity?

Answer 28

less molecules available to form chains, the more salt dissolved in water. So density not increasing between 0-4 for waters with salinities higher than 25 psu

Question 29

why does ice float?

Answer 29

Hexagonal structure less compact - lower density than liquid water
Density decreases as the freezing point is reached - ice floats
When all molecules crystaline structure density about 8% less than liquid

Question 30

whats the surface freezing point in the ocean?

Answer 30

around -1.9C

Question 31

what is negative buoyancy?

Answer 31

an abject has density greater than surrounding fluid (experiencing downward force proportional to volume)

Question 32

what is positive buoyancy?

Answer 32

object with density lower than surrounding fluid - tends to float

Question 33

why is the density of aqueous organisms so sensitive to small changes?

Answer 33

density of water similar to body density

Question 34

a change of 10 in air changes by what on land/in sea?

Answer 34

1% and 20%

Question 35

which buoyancy type are fats and oils?

Answer 35

positive

Question 36

which buoyancy type is a whale ear bone?

Answer 36

negative

Question 37

what is the adaptation of the cuttefish?

Answer 37

cuttlebone - controls amount of gas and fluid within rigid structure
- Day - negatively buoyant to hide in sediment
Dark - neutrally buoyant to hunt

Question 38

what does the swim bladder do?

Answer 38

walls have blood vessels not permeable to gases. The quantity of gas in bladder allows fish to maintain preferred depth

- Dorsal side of fish - helps stay up right 
- Sounds production

Question 39

adaptations of squid?

Answer 39

exchange sodium ions for NH3 ions creating lower density fluid, increasing the osmotic pressure allowing the organism to control its buoyancy

Question 40

what are the adaptations of crustaceans (copeopods)?

Answer 40

• During summer moths eat diatoms which leave bodies high in fat
  
  • Winter - go through diapause (at depths below 500m)
  • When they descend to start diapause the fat solidifies (usually around 500m depth) theory - stop descending when they become neutrally buoyant (kind of like dormancy)
  • This strategy uses low amounts of energy to stay at perfect depth for months (up to 6) at a time - dormancy to hide

Question 41

what are the adaptations of sperm whales?

Answer 41

before diving cold water enters spermaceti organ solidifying wax increasing the density so the whale can dive
during hunting wax warms and melts, increasing buoyancy so the whale can surface easily