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Lecture 5

BIOL 1F90 Lecture Notes - Lecture 5: Ultimate Tensile Strength, Boiling Point, Hydrogen Bond


Department
Biological Sciences
Course Code
BIOL 1F90
Professor
Fiona Hunter
Lecture
5

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Lecture 5: Biology- Continuation to first slide
Physical Properties of Water:
very polar
water weighs 18g/mole
boiling point and freezing point is high due to the water molecules wanting to
stick together
by adding or subtracting energy, the molecules move to change the state of
water
if we want to change from a solid(happy) to a liquid(happy) a lot of energy is
needed to change the hydrogen bonds to move around
Heat of vaporization: Heat requires to vaporize 1 mole of nay substance at its
boiling point under standard pressure
Fusion: when a substance goes from the liquid to the solid state and energy is
released
Heat of fusion: energy that is released during the process of fusion
Specific heat: heat required per unit of mass to raise the temperature of that
mass by one degree Celsius
Water has unique properties
High fusion will melt water, high specific heat raised temp, high heat of
vaporization cools
Cohesion: hydrogen bonding b/w water molecules gives water a high tensile
strength, molecules stick together. Pulls water to the tops of the highest trees
^ having water come apart is difficult water holds onto itself, xylem elements
(water tight tube that supplies water)
Similar to our bodies sweating to cool down
Plants sweating: transpiration (getting water from roots to leaves) process where
liquid water turns into a vapour water provides the leaves with water to cool the
plant as the plant need to be at a specific temperature to grow
When water changes state between a liquid and a solid it does something no
other molecule does. (usually when u freeze pop or beer, etc, the volume
increased causing an explosion) where this doesn’t happen to water
When water is a liquid it gets smaller- they like each other so much they can
move in closer causing a significant change in volume
Water is also called the universal solvent (things dissolve in it) related to its
dielectric constant
Salt in looking for chloride but can’t find each other because the water is in the
way, sodium and chloride will never get together if water is in the way.
Solutes: substances dissolved in a liquid
Solvent: liquid in which they are dissolved
Solution: solutes dissolved in a solvent
Hydrophilic Molecules “water loving”- readily dissolve in water, molecules
containing ionic and or polar covalent bonds are hydrophilic
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