Water and its properties
WATER IS POLAR
• In each bond, oxygen is electronegative, H
is electropositive
• Accounts for water’s being an excellent
solvent
Hydrogen bonds
• The magic of water!
• Accounts for:
– Surface tension.
– High boiling point
– High Molar Heat of Vaporization
– High Molar Heat of fusion
– Solid less dense than water (hydrogen bonds
longer in ice than in liquid water)
Ice Floats!
• Less dense than liquid water
• Due to longer and more flexible hydrogen
bonds in solid, causing empty space
• Allow for life in ponds and lakes to survive
winter—otherwise ponds and lakes may
freeze solid
• Maximum density occurs at 3.98 C—water
molecules most tightly packed then
Math With Molar Heat of Fusion
and Vaporization
• Water’s Molar Heat of Fusion:
– 6.008 kJ/mol
– Molar Heat of Vaporization: 40.79 kJ/mol
• How much heat energy is released when
506 grams of water freezes? (Molar heat
of fusion is 6.008 kJ/mol)
Another one….
• How many grams of steam releases
4.97x105 kJ upon condensation (Molar
heat of vaporization is 40.79 kJ/mol)?
Yet another one…
• How much heat energy is absorbed when
55.0 g of ice melts at STP?
Last One…
• How many grams of water is vaporized by
0.545 kJ of heat?