WATER AND THE FITNESS OF THE ENVIRONMENT. YOU MUST KNOW… THE IMPORTANCE OF HYDROGEN BONDING TO THE...
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Transcript of WATER AND THE FITNESS OF THE ENVIRONMENT. YOU MUST KNOW… THE IMPORTANCE OF HYDROGEN BONDING TO THE...
WATER AND THE FITNESS
OF THE ENVIRONMENT
YOU MUST KNOW…
• THE IMPORTANCE OF HYDROGEN BONDING TO THE PROPERTIES OF WATER
• FOUR UNIQUE PROPERTIES OF WATER, AND HOW EACH CONTRIBUTES TO LIFE ON EARTH
• HOW TO INTERPRET THE pH SCALE
• THE IMPORTANCE OF BUFFERS IN BIOLOGICAL SYSTEMS
CONCEPT 3.1
• THE POLARITY OF WATER MOLECULES RESULTS IN HYDROGEN BONDING
Water H2O• As we know - water
is polar • The end bearing the
oxygen atom has a slightly negative charge while the hydrogen atoms have a slightly positive charge
• Since oxygen is larger, it gives water a slight overall charge called polarity
POLAR BONDING
• Polarity really does allow bonding
• They are hydrogen bonds and they are very weak
• They last for fractions of a second
• Continuously break and reform
• Water has an uneven distribution of electrons between hydrogen and oxygen atoms creating polarity
• Polarity allows bonding• The bonds are very weak
hydrogen bonds • They last for fractions of a
second and continuously break and reform
+
+ -
CONCEPT 3.2
• FOUR EMERGENT PROPERTIES OF WATER CONTRIBUTE TO EARTH’S FITNESS FOR LIFE
EMERGENT PROPERTIES• COHESION ( WORKS WITH
ADHESION AND TRANSPIRATION)• SPECIFIC HEAT• INSULATION OF BODIES OF
WATER BY FLOATING ICE• ACTS AS A SOLVENT -HYDROPHILIC - WATER SOLUBLE
AND INCLUDE IONIC COMPOUNDS AND POLAR MOLECULES
-HYDROPHOBIC – DON’T DISSOLVE IN WATER AND ARE NONPOLAR SUCH AS OILS
COHESION• The natural attraction of a water
molecule to other water molecules is called cohesion
COHESION• Cohesion: attraction between
same molecules, causes molecules to draw inward at surface
• creates surface tension• Can be seen as water droplets
form
ADHESION
• The attraction of a water molecule to another polar molecule is adhesion
• Molecules such as soil and clay (dust)
• Surfaces like glass or paper straws • Certain clothing fibers and … animal
hair
ADHESION
• Adhesion: attraction between different molecules, causes water to bend at the surface and clinging of one substance
to another
ADHESION• Can be seen as water droplets
form on the spider web (another polar surface)
TRANSPIRATION1. We know that gravity is
ALWAYS pulling on objects with mass
2. Yet water can move up a plant with relative ease - How can this happen?
3. The water molecules cling to each other by cohesion and water and minerals cling to the walls of the xylem tubes by adhesion
4. This property of adhesion is called capillary action
Review of Polarity
Polarity hydrogen bonding
cohesion adhesion
surface tension capillary action
Forces
Properties
Forces
SPECIFIC HEAT
• The amount of heat required to raise or lower the temperature of a substance by 1 degree Celsius
• Water exhibits evaporative cooling: removes heat when it evaporates from a surface
• Ex: sweating cools skin
INSULATION
• Water expands during freezing: expands into crystal formation releasing heat
• Ex: rocks broken up by ice creating soil; ice layer protects
fruit from freezing
SOLVENT
• Dissolves many other substances due to polarity
• Differences in charges pulls/pushes substances apart
• HYDROPHILIC SUBSTANCES – are water-soluble and may be polar
• HYDROPHOBIC SUBSTANCES – are nonpolar and do not dissolve in water EX. oils
CONCEPT 3.3
• ACIDIC AND BASIC CONDITIONS AFFECT LIVING ORGANISMS
Acids, Bases and the pH scale
The pH scale measures the concentration of H+ ions (how acidic something is)Ranges from 0-14At 7: H+ ions and OH- ions are equal so it is neutral 0-7: acidic, has more H+ ions 7-14: basic, has more OH- ions
• ACIDS: release H+ when mixed with water
• Sour, corrosive• Ex: HCl, H2SO4
• Always have H at front of formula
• BASES: release OH- when mixed with water
• Bitter, slippery, usually in cleaners
• NaOH, CaOH• Always have OH at end
of formula
What is a buffer?• Buffers are weak acids or bases that
react with strong acids and bases to prevent sharp changes in pH
• Helps to neutralize• Help to control pH in blood, digestive
tract, etc. to maintain homeostasis