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Chapter 3

BIO SCI 93 Chapter 3: Bio Sci 93: Chapter 3- Water and Life

Biological Sciences
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3.2 Four Emergent Properties of Water
Cohesion of Water Molecules
- Cohesion: hydrogen bonds is a phenomenon
- Adhesion: clinging of one substance to another
- Surface tension: a measure of how difficult it is to stretch or break the surface of a liquid
Temperature and heat
- Anything that moves has kinetic energy
- The faster a molecule moves, the greater its kinetic energy
- The movement of molecule is called thermal energy
- It is related to temperature
- Temperature: measure of energy that represents the average kinetic
energy of a molecule in a body of matter
- When two objects are brought together, thermal energy transfers from warmer to cooler
until it is same temperature
- Heat: thermal energy in transfer from one body of matter to another
- One convenient unit of heat is called calorie (cal)
- 1000 cal = 1 kilocal (kcal)
- Another unit is Joule (J)
- 1 J = 0.239 cal
- 1 cal = 4.184 J
Water’s specific heat
- Specific heat: amount of heat that must be absorbed or lost for 1g of that substance to
change its temperature by 1oC
- Can be seen as how well it resists to temperature change
- Water’s specific heat is 1 cal/g* oC
Evaporative Cooling
- Heat of vaporization: the quantity of heat a liquid must absorb for 1g of it to be converted
from the liquid to the gaseous state
- High amount of energy required to vaporize water has a wide range of effects
- Evaporative Cooling: when “hottest” molecules with greatest kinetic energy leaves as
Floating Ice on liquid water
- Ability of ice to float is due to its lower density
- If ie could sink, all ponds, lake, and oceans would freeze solid, making life impossible.
Water: Solvent of Life
- Solution: liqud that is a completely homogeneous mixture of two or more substances
- Solvent: dissolving agent of a solution
- Aqueous solution: one in which the solute is dissolved in water, and water is solvent
- Hydration shell: sphere of water molecules around each dissolved ion
Hydrophilic and Hydrophobic
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