A1.1 water Flashcards
oh god
how are hydrogen bonds formed
- sharing of electrons is not equal in H2O
- oxygen atom with more protons attracts electrons closer = assumes a partial negative charge = water molecules are polar
- As the molecules are polar, hydrogen bonds can be formed btwn a -ve O and +ve H
- ## each water molecule can form 4 hydrogen bonds with surrounding water molecules
Describe cohesion and adhesion
Cohesion: the attraction btwn the same kind of molecules
- H2O molecules attracted to other H2O molecules, forming h-bonds btwn the -ve O atom of a molecule and the +ve H atom of another molecule
Adhesion: the attraction btwn different kinds of molecules
- polar water molecules attracted to other polar molecules, forming H-bonds
Applications of cohesion (2)
- allows for SURFACE TENSION due to the cohesive nature of water molecules (animals walk on water etc.)
- surface tension is the effect of water molecules being attracted to one another (by h-bonding) stronger than to air particles.
- cohesive forces allow water molecules to be drawn up xylem vessels in plants by evaporative loss through the stomata in the leaves = water is sucked upwards from roots to leaves along the tubular vessels in xylem tissue.
- cohesive nature of polar water molecules allows water to form a continuous column of water molecules moving up the xylem = as long as the column is continous, the hydrogen bonds allow water in xylem to withstand tensions and water is pulled upwards
FOR BOTH APPLICATIONS,
multiple h-bonds must be broken simultaneously for a column of water to break/object break through the water surface
Application of adhesion
CAPILLARY ACTION IN PLANT CELL WALL
- water adheres to cellulose molecules in cell walls = dry wall is immediately rewetted if water avaliable
- If water is lost through the leaves to the atmosphere, adhesive forces draw water out of the nearest xylem cell, GENERATING low pressures that draw water up in xylem vessels
- IF a xylem vessel becomes air-filled, adhesion btwn water and the wall of the vessel helps the vessel to refil with water
E.G. xylem vessels in deciduous vessels (trees that lose their leaves for a part of the year) are air-filled throughout winter. During spring, capillary action due to adhesion helps sap to rise, refilling the xylem vessels.
- The apoplast pathway allows water and dissolved nutrients to move through the cell wall, as cellulose is porous and polar = water moves from cell to cell by capillary action through the cell wall, as polar water adheres to the polar cellulose
Do polar molecules dissolve in water?
yes!!
2 examples of an animal adapted for buoyancy.
Black-throated loon:
- Has the ability to swing long distances underwater
- However, common bird anatomy has hollow bones to decrease weight, and air trapped in feathers for insulation = problematic in water as buoyancy needs to be overcome to catch underwater prey
- Hence the black-throated loon has SOLID BONES to increase weight
- Can compress air from its lungs and feathers to decrease buoyancy = enable successful diving
Ringed seal:
- subcutaneous fat/blubber acts as a buoyancy aid
- seals also have claws to dig through ice to make holes to emergy from their aquatic habitat and breathe = can live on and under the ice
What is a goldilocks zone
- temperature in the zone allows water to exist as a liquid state
- to close to a star, water vapourises, too far, water freezes
one hypothesis for the extraplanetary origin of water on earth
- There is evidence of heavy bombardment of asteroids during the first few hundred million years after Earth’s formation
- It is likely that these asteroids contained water
- When these asteroids enter orbit and heat up, they release their water as gas, which is trapped by Earth’s gravitational field
- The distance from Earth to the sun ensures that temperature is never high enough for water to boil, but not low enough for water to freeze, and just cool enough for water vapour to condense into water
- Due to Earth’s size it is able to hold the oceans tightly to its surface and hold gases within the atmosphere
2 examples of animals adapted for thermal conductivity
Black-throated loon:
- traps air in feathers = effective insulating layer btwn skin and outside air
- feathers restrict convection currents by trapping a thin layer of air that does not move easily = maintain body temperature of the bird
Ringed seal:
- Has thick blubber to insulate its body.
- fat is stored as adipose tissue under the skin = subcutaneous fat/blubber
- seals also have claws to dig through ice to make holes to emergy from their aquatic habitat and breathe = can live on and under the ice
What is viscosity + factors affecting it
- the stickiness of a fluid = determines how easily it can flow
- Viscosity is due to internal friction when one part of a fluid moves relative to another part
- move viscous = more resistance and drag
- solutes INCREASE viscosity
viscosity is affected by:
- altitude
- temperature
