Flashcards in water Deck (19):
geometry of water
the ideal angle of tetrahedral is ___ degrees, but repulsion of e- from H pushes H together to ___ degrees
each water molecule can form H bonds with ___ other water cules to form an inter-molecular network
H-bonds hold water molecules ___% closer together than without H-bonds
the anomalous properties of H2O are due to its _____ H-bonds
why are H2O MP and BP so unusually high?
because of the H bonds
why does top freeze and bottom remain liquid?
because the bottom is 4 degrees, which is heaviest, so it stays at the bottom; meanwhile ice volume is larger, it floats on top
what is phase transition?
the transformation of a thermodynamic system from one phase to another
what are the 5 different phases of water?
liquid, vapour, solid, glass, supercritical fluid
food with aw > ___ and pH > ___ are regarded as potentially hazardous
what are humactants?
salts, sugars, glycerol that prevent moisture migration from high water activity bread to the fillings
army rations are baked at ____ F
what is the latent heat of vapourization of water?
what is the latent heat of fusion of ice?
what do the colligative properties of water solely depend on?
the number of solute molecules dissolved
dissolving of solute ___ vapour pressure, ___ freezing point, ____ boiling point
lowers; lowers; raises
how is water activity calculated?
aw=vapour pressure of food (p)/vapour pressure of pure water (po)
what are the three states of water in food?
bound, capillary, free