NDFS 250 Water~~

• Solvent and dispersing or bulking agent
• reactant (hydrolysis reactions)
• rheology and texture
• microbial growth (spoilage)
• medium for heating and cooling foods
• cleansing agent
• transport
• mechanical processes (water knife!!! cool~~
• )

unequal sharing of electrons... you know la

• + dislike +
• - like +

you knkow la

dipolar nature of the water molecule allows it to engage in hydrogen bonding, ion-dipole, and dipole-dipole interactions with other polar or charged molecules

composition of solute and solvent

• unsaturated solution
• saturated solution
• supersaturated solution

• the nature of the solvent
• the nature of the solute
• the concentration of solute molecules present

• boiling point _.-^
• (instead of overcoming h-bonding, it's OH- in sugar... ion &dipole force now)

freezing point ^-._

• hydrogen bonding forces
• atomspheric pressure pushing down on the surface

• for every 960 ft
• decreases 1 *c

• properties of a solution that depend upon the number of molecules present, not upon their nature/size
• vapor pressure
• boiling point
• freezingpoint
• osmotic pressure

g/mol

• concentration (moles) or solute/ 1000gm of solvent
• concentration (moles) or solute/ 1000mL of solution

they're basically the same because 1gm water = 1mL water

*2!

• bp raises .052 C
• fp drops 1.86 C

• evaporation
• freezing
• melting (fusion)
• sublimation
• vaporization
• condensation

• 80 cals from 0c ice to 0c water
• 540cals from 100c water to 100c steam

the amount of energy required to raise 1 gm of thing 1C*

when the thing is water = calarie/ gm

• change in temperature produced by heat; when all the heat added results in temperautre change in the substance, it is know as sensible heat.
• can be measured with a thermometer

• cannot be removed by normal drying
• no longer acts as solvent for solutes
• not available for biological growth/function
• has no appreciable vapor pressure
• only freezes at very low temperatures (<-5*c)
• needs high pressure to be removed from tissues

• total water content (moisture)
• water activity (available water)

• a measure of free or available water
• vapor pressure of sample/vapor pressure of pure water

btw 0-1

1

.91

.88

.80

0.75

0.65

.60