FND300 - First Lecture (water properties)

Characteristics of water in liquid phase

in motion; continuous breaking and reformation of hydrogen bonds

Characteristics of water in as it cools towards freezing

molecules slow down and pack closer; volume decreases; subsequently density increases

Characteristics of completely frozen water (ice)

water molecules lock into a fixed hexagonal crystal lattice structure

hydrogen bonds push water further apart and create small pockets

volume increases

density decreases due to expanded volume

Conductivity

the rate at which heat flows/transfers by conduct

Conductivity of Ice Compared to water

conductivity of ice is 4x greater than water

Diffusivity

the rate at which a substance undergoes a temperature change

Diffusivity of Ice compared to Water

the diffusivity of ice is 9x greater than water

What process occurs more rapidly - thawing or freezing and explain why

freezing -- Freezing (Faster)

What type of interaction occurs between ions and water

dipole-ion interaction

Dipole-ion interaction strength compared to hydrogen bond

greater

What type of interaction occurs between ions and charged peptides, amino acids or proteins

dipole-ion interaction

What type of interaction occurs between ions and uncharged peptides or proteins

dipole-dipole interaction

Dipole-dipole interaction strength compared to hydrogen bond

equal

What type of interaction occurs between water and lipids

hydrophobic interaction

What type of interaction occurs between water, lipids and emulsifier

emulsion

How does emulsifier create an emulsion

by possessing hydrophilic heads and hydrophobic tails

Hydrophobic interaction strength compared to hydrogen bond

weaker

How molecules/ions disrupt water intermolecular hydrogen bonding (list the two steps)

disrupt the tetrahedral arrangement; step 1 - the first layer of water surrounds ions ; step 2 - the second layer of water is disrupted by ions because dipole-ion interactions compete with hydrogen bonding

Bulk water

water that is unaffected by structure breakers

Structure Breakers Characteristic and Function

large monovalent ions that disrupt hydrogen bonding in water

Structure Breaker Examples

K^+, NH4^+, Cl^-, NO3^-

Structure Former Characteristic and Function

small monovalent or multivalent ions that enhance hydrogen bonding

Structure Former Examples

Ca^2+, Na^+, Mg^2+, OH^-