2 Water as a vehicle for life Flashcards
hydrogen bonding
attraction between H atom in a polar covalent bond and another electronegative atom
Oxygen
stronger attraction for electrons (more electronegative-pulls electrons toward it)
solution
liquid that is a homogenous (of the same) mixture of substances
solute
dissolving agent of a solvent and a substance which is dissolved
aqueous solution
water is the solvent (each ion is surrounded by a hydration shell)
hydration shell
the sphere of water molecules around each dissolved ion
Cations
- positive ions
- oxygen closet
anions
- negative ions
- hydrogen closet
Water as a solvent can dissolve many types of solutes:
- Ionic molecules
- compounds made of non-ionic polar molecules
- large polar molecules (ex. proteins) if they have ionic and polar regions
hydrophilic substance
has an affinity for water (relatively polar bonds)
hydrophobic substance
does not have an affinity for water (relatively non-polar bonds)
H-bonding in ice is more ordered than in liquid water because…
- ice is less dense than water
- ice is solid and has a larger volume
freezing point depression
presence of solutes decreases the freezing point of a solvent (seawater)
Hydrogen bonds are constantly…
breaking and reforming
What can high concentrations of solutes in some organisms do in cold climates?
can prevent body fluids from freezing
Glycerol concentration in smelt blood (plasma)….
increases as temperature decreases
liquid water
hydrogen bonds break and reform
ice
hydrogen bonds are stable
are cohesion and adhesion important in water transport in plants?
Yes
Cohesion
sticking together (the hydrogen bonds hold the substance together)
Adhesion
the clinging of one surface to another
adhesion of water by hydrogen bonds to the molecules of cell walls helps counter the downward pull of gravity
as a result of hydrogen bonding what do water molecules do?
they stay close to each other
surface tension
how hard it is to break the surface of a liquid