1. Objectives for this week…
 Generate an empirically evidenced and logical argument.
 Distinguish a scientific argument from a non-scientific argument.
 Recognize methods of inquiry that lead to scientific knowledge.
 List features that distinguish living organisms from nonliving
matter.
 Explain what is meant by the term diversity, and speculate about
what caused the great diversity of life forms on Earth.
 List as many steps of the scientific approach to understanding a
problem as you can.
 Know the various types of chemical bonds, the
circumstances under which each forms, and the
relative strength of each type
 Understand the essential chemistry of water, the
relationships of acids, bases, and salts.

3. Why do we need to learn about
Chemistry?
Chapter 2
Basic Chemistry
Chemistry: “The study of matter
& the changes it undergoes.”
-Chang, R. (2007). Chemistry. 9th ed.
McGrawHill: New York

4. Life is
made of
chemicals!

5. Why Chemistry?
Life uses
chemical
reactions!

6. Why Chemistry?
Life uses
chemical
reactions!

7. What are we going to talk about
today?
Chemical elements
Compounds and molecules
Chemistry of water
Acids and bases

8. Protons
Electrons
Neutrons
Chemical Elements
• Matter: anything that takes up space and has
mass (solids, liquids, gases)
• All matter is made of elements: cannot
be broken down
Oxygen
An element!
+
+
+
+
+ +
+
+
-
-
--
-
-
-
-
Atom: smallest unit of an
element
Water
Not an element!
Hydrogen
John Dalton

9. Chemical Elements
CHNOPS =
95% body
weight of
organisms

10. Chemical Elements
Helium

11. Electrons are
attracted to the
positively charged
nucleus
Chemical Elements
(-)(+)
Most stable
Less stable
Valence shell: Outer electron
shell
Valence electrons: # of
electrons in valence shell
Octet rule: outer shell is most
stable with 8 electrons

12. Chemical Elements
• Isotopes
– Same # of protons and
electrons
– Different # of neutrons
• Ions
– Different # of electrons
– Have charges, instead
of being neutral
Na Na+

13. Chemical Elements
• Way to organize the
elements
• Groups - similar
characteristics
– Same valence electrons
• Periods – same #
valence shells
• Atomic mass
– Average mass for all the
isotopes
– Slightly different than
mass number
Periodic Table

14. Chemical Elements
Handwritten
Periodic Table
Which isotope you are talking about
Average mass of all isotopes

15. Chemical Elements
Carbon Isotopes – How many neutrons?
6 7 8
Unstable – radioactive!

16. Chemical Elements
• Radioactivity - releases
energy (as well as
other particles)
• Radioactive isotopes
can be used as medical
tracers (low levels)
• High levels can be used
to kill bacteria and
cancer

17. What are we going to talk about
today?
Chemical elements
Compounds and molecules
Chemistry of water
Acids and bases

18. Compounds and Molecules
• Compound vs.
molecule
• Compound 2 different
elements
• Molecule has same
elements
• In Biology, everything
is a molecule! 
http://dl.clackamas.edu/ch104-03/molecule.htm
Water
Molecular
Oxygen

19. Compounds and Molecules
• Ionic Bonding
– Transfer of electrons
from one atom to
another
– Causes (+) and (-)
charged ions
– Attracted to each other
– Salts: solid substances
that usually separate and
exist as individual ions in
water

20. Compounds and Molecules
• Covalent Bonding
– Two atoms share
electrons to fill outer
electron shell
– Single, double, triple
bonds
– Non-polar covalent bond
= equal electron sharing
– Polar covalent bond =
unequal electron sharing
 water!!

21. Which do you think is the strongest, ionic
or covalent bonds? Why?

22. What are we going to talk about
today?
Chemical elements
Compounds and molecules
Chemistry of water
Acids and bases

23. Chemistry of Water
Water (H2O)
is polar
covalent
Oxygen is very electronegative
Hydrogen
bonding
between
molecules

24. The discovery of liquid water under the frozen
surface of a distant moon in our solar system
has caused scientists to speculate on the
possibility of life on that moon. Researchers
hold no hope of any life form existing on any
planet or moon in the absence of water.
Why?

25. Chemistry of Water
• Properties
1. High heat capacity
2. High heat of evaporation
3. Solvent
4. Cohesion & adhesion
5. Frozen water is less dense than liquid water

26. Chemistry of Water
High Heat Capacity
Good for organisms
that this occurs slowly!

27. Chemistry of Water
High Heat of Evaporation

28. Chemistry of Water
Water is a Solvent
• Universal solvent
• Hydrophilic –
molecules that can
attract water (ions,
polar molecules)
• Hydrophobic –
molecules that cannot
attract water
(nonpolar molecules,
neutral atoms)

29. Chemistry of Water
Cohesion & Adhesion

30. Chemistry of Water
Frozen water is less dense than liquid water

31. Review: Chemistry of Water
• Polar covalent bond
within the molecule
• Hydrogen bonds
between molecules
• 5 Properties
1. High specific heat
2. High heat of
vaporization
3. Is a solvent
4. Cohesion and
adhesion
5. Frozen water is less
dense than water

32. What are we going to talk about
today?
Chemical elements
Compounds and molecules
Chemistry of water
Acids and bases

33. Acids and Bases
When water dissociates (ionizes) 
equal # of hydrogen ions and
hydroxide ions
Only a few at a time do this

34. Acids and Bases
Acids
• Dissociate in water 
releasing H+
• Strong acid almost
completely dissociates
HCl  H+ + Cl-
Bases
• Uptake H+ or release
OH-
• Strong base almost
completely dissociates
NaOH  Na+ + OH-How do we
measure
this?

35. Acids and Bases
• pH scale: measurement
scale for hydrogen ion
concentration
• >7 basic
• <7 acidic
• =7 neutral
• Log scale
– each increase in
number = 10X increase
100X more acidic
than water
10,000,000X more
acidic than water

36. Acids and Bases
• Buffers: chemical or
combination of
chemicals that keep pH
within normal limits
– Blood pH needs to stay
about 7.4
– At 7, acidosis
– At 7.8, alkalosis
H2CO3 H+ HCO3
-
dissociates
re-forms

37. Acids and Bases
• Acid precipitation (deposition) has a pH <5
• Sulfur dioxide and nitrogen oxides from fossil
fuel emissions such as coal, oil, and gasoline
• Lakes, forests, structures

38. What are we going to talk about
today?
Chemical elements
Compounds and molecules
Chemistry of water
Acids and bases
Any Questions?

39. Review Questions
About 25 of the 92 natural elements are known to
be essential to life. Which four of these 25
elements make up approximately 96% of living
matter?
A) carbon, sodium, chlorine, nitrogen
B) carbon, sulfur, phosphorus, hydrogen
C) oxygen, hydrogen, calcium, sodium
D) carbon, hydrogen, nitrogen, oxygen
E) carbon, oxygen, sulfur, calcium

40. Review Questions
How do isotopes of the same element differ
from each other?
A) number of protons
B) number of electrons
C) number of neutrons
D) valence electron distribution
E) amount of radioactivity

41. Review Questions
A covalent chemical bond is one in which
A) electrons are transferred from one atom and to
another atom so that the two atoms become
oppositely charged.
B) protons and neutrons are shared by two atoms.
C) outer-shell electrons of two atoms are shared.
D) outer-shell electrons of one atom are transferred to
the inner electron shells of another atom.
E) the inner-shell electrons of one atom are transferred
to the outer shell of another atom.

42. Review Questions
Protons =
Neutron =
Electrons =
7
8
7
Atomic Number
Mass Number

43. Review Questions
Ca
2+
Protons =
Neutron =
Electrons =
20
20
18

44. Review Questions
Atomic Mass
Atomic Number
Atomic Symbol

45. Resources
• Bombardier beetle
– http://www.pnas.org/content/96/17/9705.full
• History of the Atom
– http://www.chemheritage.org/discover/chemistry
-in-history/themes/index.aspx