1. Biology Intro…. Chapter 1: Themes in the Study of Life
Chapter 2: Chemical Context of Life
Chapter 3: Water and the Fitness of the Environment

2. Unifying Themes in Biology
Evolution~ biology’s core theme; differential reproductive success
Emergent Properties~ hierarchy of life
The Cell~ all organism’s basic structure
Heritable Information~ DNA
Structure & Function~ form and function
Environmental Interaction~ organisms are open systems
Regulation~ feedback mechanisms
Unity & Diversity~ universal genetic code
Scientific Inquiry~ observation; testing; repeatability
Science, Technology & Society~ functions of our world

3. Chemical Context of Life
Matter (has volume & mass)
Atom: the smallest unit of matter that still retains the physical & chemical properties of its element.
Sub-atomic Particles:
Neutrons- no charge, in nucleus, 1 amu
Protons- (+) charge, in nucleus, 1 amu
Electrons- (-) charge, orbit around nucleus negligible mass.
Atomic number - # of protons;
in a neutral atom, # of protons = # of electrons
Mass number - protons + neutrons of an atom
Atomic Weight takes into consideration all of the isotopes of that element and averages them….
Isotopes- Atoms of an element that have the same # of protons, but different # of neutrons.
same atomic number, different mass number

4. Structure of an Atom
The nucleus of an helium atom contains 2 neutrons, shown in purple and 2 protons, shown in green. 2 electrons move around the nucleus at very extreme speeds.
Question: How many neutrons would there be in Carbon 14?
a b c d. 28

5. Reading the Periodic Table
Fluorine
Chemical Symbol: F
# of protons:
# of electrons:
# of neutrons: 9 2 7 F 9 19 9
= 10

6. Energy Levels & Orbitals….
Energy Levels- also referred to as “shells”
Made up of orbitals
Orbital: the 3 dimensional space where the electrons are found
No more than 2 electrons per orbital
“s” orbital-
spherical
found in all shells
Holds just one pair of electrons
The first shell only has the one S orbital
“p” orbital-
Dumbbell shaped
Found in higher energy levels (shells)
3 p orbitals per shell
Electron Configuration- the main property which determines chemical behavior.
How many electrons are in a shell that has all its s and p orbitals filled?
A B C D. 8

7. Energy Levels & Orbitals….
Valence Electrons- electrons in outer most shell
Not to be confused with….
“Valence” – the bonding capacity of an atom; the number of covalent bonds that must be formed to complete the outer shell’s “octet”.
Octet Rule: a shell is complete when it contains 8 electrons (or “feels” like it does).
H and He exempted
Atoms with incomplete valence shells are chemically reactive.
Molecule- 2 or more atoms held together by chemical bonds.
Bonds- attractions that hold molecules together.
Animation

8. Chemical Bonding Covalent Double covalent Nonpolar covalent
Ionic
Hydrogen
van der Waals

9. Covalent Bonding Sharing pair of valence electrons
Number of electrons required to complete an atom’s valence shell determines how many bonds will form
Ex: Hydrogen & oxygen bonding in water; methane
Animation

10. Polar/nonpolar covalent bonds
Electronegativity attraction for electrons
The difference in electronegativity determines if atoms are:
Non-polar covalent (very little to no difference)
Polar covalent (somewhere in the middle)
Ionic (big difference)
Non-polar covalent •electrons shared equally •Ex: diatomic H2 and O2
Polar covalent •one atom more electronegative than the other (charged) •Ex: water
Water is a _________ molecule.
A. Ionic
B. Non-Polar Covalent
C. Polar Covalent

11. Polar/nonpolar bonds

12. Ionic bonding
High electronegativity difference strips valence electrons away from another atom
Electron transfer creates ions (charged atoms)
Cation (positive ion); anion (negative ion)
Ex: Salts (sodium chloride)
Animation

13. Hydrogen bonds
Hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom (oxygen or nitrogen)
Hydrogen Bonding occurs:
A. Between Polar Molecules.
B. Between non-polar molecules.
C. Between ionized atoms.
D. Between ionic molecules.
Animation

14. van der Waals interactions
Weak interactions between molecules or parts of molecules that are brought about by localized change fluctuations
Due to the fact that electrons are constantly in motion and at any given instant, ever-changing “hot spots” of negative or positive charge may develop

15. Water Jesus lizard Polar~ opposite ends, opposite charges
Weakly (+) at the Hydrogen; weakly (-) at the Oxygen
This causes: HYDROGEN BONDING!!!!
Cohesion~ H+ bonds holding molecules together
Adhesion~ H+ bonds holding molecules to other substance
Surface tension~ measurement of the difficulty to break or stretch the surface of a liquid
High Specific heat~ amount of heat absorbed/lost to change temperature by 1oC. Resists Temp changes!
(for water, that’s 1 calorie)
Heat of vaporization~ quantity of heat required to convert 1g from liquid to gas states. This, too, is high for water which leads to….
Evaporative Cooling~ Molecules with the highest energy escape first, leaving the average energy of the system proportionally MUCH lower.
Density……….
Jesus lizard

16. Density & Solvency:
Due to hydrogen bonding, water is less dense as solid than liquid
Crystalline lattice keeps molecules at a distance
Water is the “Solvent of Life”
Hydrophilic (water loving) solutes dissolve in it: They include:
Ionic Compounds- water surrounds the individual ions, separating and shielding them from each other.
Polar Compounds- charged regions have affinity for oppositely charged regions of polar molecules.
Don’t forget your molarity!
Ionic Animation
What is Molarity?
A. Moles solvent / Liter Solute
B. Moles solute / Liter Solvent
C. Grams solvent / Liter Solute
D. Grams solute / Liter Solvent

17. Acid/Base & pH Water Animations
Dissociation of water into a hydrogen ion and a hydroxide ion
2H2O  H3O+ + OH-
Acid: increases the hydrogen concentration of a solution
Considered to be “proton donors”
pH between 0 and 7
Base: reduces the hydrogen ion concentration of a solution
Considered to be “proton acceptors”
pH between 7 and 14
pH = -log[H+] (example on next slide)
Buffers: substances that minimize H+ and OH- concentrations (accepts or donates H+ ions)
Acidification of the Oceans