Water Flashcards
Water comprises…
approx 70% plus of human mass:
45-60% intracellular
25% extracellular/blood plasma
Properties of water: (6)
Cohesion and adhesion
High specific heat and heat of vaporization
Polarity
Hydrogen bonding potential
Water is nucleophilic
Water weakly Ionizes
Cohesion:
refers to attraction to other water molecules.
- responsible for surface tension
Adhesion:
refers to attraction to other substances.
- Water is adhesive to any substance with which it can form hydrogen bonds.
- Adhesion to hydrophilic substances
e.g. cellulose
- Not to hydrophobic substances
e.g. waxes
Water stores…
Heat
High specific heat:
Amount of heat that must be absorbed or expended to change the temperature of 1 g of a substance 1o C
High heat of vaporization
Amount of energy required to change 1g of liquid water into a gas (586 calories).
– large number of hydrogen bonds
The Polar Nature of Water:
- Given the difference in electronegativity between oxygen and hydrogen (3.5 - 2.1 = 1.4) and its shape, water is a polar molecule with a dipole moment
- Net charge on oxygen is -0.66 and that on each hydrogen is +0.33
(pg 51)
Water is polar:
-there is an asymmetric internal
distribution of charge due to oxygen’s two pairs of unshared electrons
-Hydrogen Bonding Ability
Water has hydrogen bonding potential:
- H-bonds are non-covalent, weak interactions
- H2O is both a hydrogen donor and acceptor
- One H2O can form up to four H-bonds
A water molecule forms 4…
hydrogen bonds, one through each hydrogen donor and one through each lone pair on the oxygen acceptor
(pg 55)
The molecular structure of water can assume…
many forms including
Ice 1, Ice 9, and Ice 12
Water and H-bonds:
High specific heat
Lots of heat is needed to break H-bonds and raise H2O temperature. Therefore, H2O is a good insulator.
