LIFE 102 Lecture Notes - Lecture 3: Chemical Polarity, Surface Tension, Heat Capacity
Biology 8-26-16 – 8-29-16: Chapter 3:
Properties of Water
• Water is essential for all life on earth
o Organisms are 70-95% water
o Polar bonds within molecules, hydrogen bonds between
molecules
• What is so special about water?
o Cohesive
o Moderates temperature
o Expands upon freezing
o Excellent solvent
▪ All due to the fact that water is a polar molecule.
• 1) Cohesiveness of Water
o Polar covalent bonds within water molecules
o Hydrogen bonds between water molecules
▪ Helps with the transport of water and nutrients from
the bottom to the top of plants
o Also means that water has a high surface tension
▪ How hard it is to stretch/break the surface of a liquid
• 2) Water moderates changes in temperature
o Water has an unusually high specific heat
o Water changes its temperature less than other liquids when
it absorbs the same amount of energy
o Water heats up: hydrogen bonds are broken - heat is
absorbed
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