Section 3, 1 st 9 Weeks Notes

 Investigate the properties and importance of water and its significance for life:  surface tension  adhesion  cohesion  polarity  pH  Learning Expectations

 Atom  Electron  Proton  Neutron  Nucleus  Element  Compound  Polar Molecule  Hydrogen bond  Solute  Solvent  Solution

 Progression, or Hierarchy, of Life, from smallest to largest › Atoms, molecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, biomes, biosphere

 ATOMS: The building blocks of matter  All atoms are made of subatomic particles › PROTONS: Positively-charged particles › ELECTRONS: Negatively-charged particles › NEUTRONS: Neutrally-charged particles

 Protons and neutrons compose the NUCLEUS › The center of an atom  # of protons determines the element  The atomic # is the # of protons  Electrons found in “orbits” around nucleus

 ELEMENT: A pure substance that cannot be broken down into simpler substances by physical or chemical means  The smallest unit of an element is an atom  Ex: Oxygen, Calcium, Hydrogen

 Elements can combine to form COMPOUNDS › A pure substance formed from two or more different elements  Every compound represented by a chemical formula made of chemical symbols

› Ex. C 6 H 12 O 6 is the chemical formula for GLUCOSE › C is symbol for carbon, H for hydrogen, etc › Formula says the compound has:  6 carbon atoms  12 hydrogen atoms  6 oxygen atoms

 Elements can share electrons to form molecules › Water, carbon dioxide, glucose are molecules

 All chemical reactions in organisms occur in water  Important properties of water are caused by it being a POLAR MOLECULE › Molecule that has an unequal distribution of charge › Slightly negative oxygen and slightly positive hydrogen

 Negative oxygen is attracted to positive hydrogen of another water molecule › HYDROGEN BOND: Weak, electrostatic bond between water molecules › Will always be shown as dotted lines between two atoms of different molecules  POLARITY of water gives it unique and important properties

 #1 Cohesion › Attraction to other water molecules › Creates water’s high surface tension › Belly flops hurt

 #2 Adhesion › Attraction of water to other surfaces › Allows water to travel up trees (capillary action)

 #3 High Specific Heat › Water absorbs high amounts of energy before changing temp › Good for THERMOREGULATION  Maintaining body temperature in animals

 #4 Water expands when frozen › Ice becomes less dense than liquid water › Shatters easily because of weak bonding › Due to hydrogen bonding

 #5 Dissolves many substances › SOLUTE: Substance dissolved in a SOLVENT › SOLVENT: Substance in which another substance is dissolved in › SOLUTION: Homogeneous mixture when a solute is dissolved in a solvent

 Water is the universal solvent  Polar substances will mix with and dissolve other polar substances  Polar will not mix with or dissolve nonpolar substances  “Like dissolves like”  Think oil and water › Oil = nonpolar and water = polar

 Explain what all atoms have in common. Explain what makes atoms of different elements different.  Identify the elements and how many of each in the following compounds › NaCl › CO 2 › NH 3 › CH 4  C 12 H 22 O 11  Al 2 O 3  H 2 O

 Explain how a molecule becomes polar. What very important substance is polar?  Explain how a hydrogen bond works. Is oxygen the only element that forms a hydrogen bond with hydrogen? Do some brief research and tell me what other elements will do this.  Draw five water molecules that are hydrogen bonded.  List the five properties of water and how each one can be important to life.