1. The Chemical Basis of Life
Chapter 4
The Chemical Basis of Life

2. What are we? (all living things)?
Bubbling beakers of chemical reactions, we call “LIFE”…

3. 4.1 Life involves… A. Matter Anything that occupies space and has mass
Physical “stuff” of the universe
3 states: solid, liquid, gas

4. 4.1 Elements & Compounds… a. Elements Pure substance,simplest form
Made up of 1 type of atom
Ex: Hydrogen (H), oxygen (O), nitrogen (N)
~110 elements on Periodic Table

5. Open your Agenda….
Page 124

7. 4.1 Elements verses Compounds…
2 or more elements
Chemically combined in a fixed ratio
Written as formulas
Ex: water – H2O
carbon dioxide – CO2
sugar –C6H12O6

8. 4.1 Elements used to make the compounds found in the human body
Chemical Symbol Mass (70Kg person)
O Kg
C Kg
H Kg
N Kg
Ca Kg
P g
K g
S g
Trace elements make up <0.01% of your body

9. Important Elements in Life….
C HOPKINS CaFe Mg NaCl
(What elements are represented here?)

10. The Most abundant elements in Life….
What does a goose say???
HONC
(What elements are represented here?)

11. Now then. What are atoms?
Basic building blocks of matter
A desk, the air, & you are made up of atoms!

12. What everything is made of: basic structure
Electron shell

13. 4.2 Atoms are made out of 3 basic particles…
Electrons
Negative charge, no mass

14. within the nucleus… Proton – positively charged
Neutron – no charge (neutal)
Mass of each is equal. Together, give matter its mass (weight)

15. To make living things, we bond atoms into molecules
2 types of bonds that hold atoms together:
Covalent
Ionic

16. 4.3 Covalent Bond
A bond formed when atoms share electrons
Molecules form when 2 or more atoms are connected by covalent bonds

18. 4.3 Ionic Bond
A bond formed when an electron is transferred from 1 atom to another (one atom gains an electron; another atom loses it.
Atoms become + or - ions

19. An ionic bond forming by transferring an e- from Na to Cl

20. Molecular structure is shown as a ‘molecular or structural formula’…
Molecular: shows the kind of and the number of atoms
Structural: shows the arrangement of atoms in a compound (the bonds)

21. Molecular formula of water
H2O
Structural formula
of water

22. Molecular formula of glucose
C6H12O6

23. Structural formula of glucose

24. 4.3 Chemical Equations Represent a chemical reaction
Ex. 2 H2 + O2  2 H2O

25. 4.3 Reactants & Products
Reactants = the chemicals on the LEFT side of the equation 
Products = the chemicals on the RIGHT side of the equation (are made or produced in the reaction)

26. Balanced equations
2 H O2  2H2O

27. 4.3 Balanced Equation Example
H2 + O2  H2O
is unbalanced
Why?

28. 4.3 Balanced Equations
To BALANCE equations, add COEFFICIENTS in front of the compounds
(go back and balance w/ coefficients)

29. 4.4 Why Life depends on water

30. 1. Because H2O molecules are POLAR, they are weakly bonded together

31. This attraction = ‘Cohesion’; molecules of the same kind “stick” to one another
Adhesion – attraction between unlike molecules
Trees depend on these forces!! How??

32. 2. Water is a solvent Ex. Dissolving salt into water
Other substances dissolve in water. They will not separate out
Ex. Dissolving salt into water

33. 4.4 solutions contain:
1. The solvent – liquid that other substances are dissolved in. is The 1 in greater quantity
(ex, Water , the “universal solvent”, because so many things disslove in it)
2. And the solute(s) – substances dissolved . Present in lesser amounts Ex. salt

34. When water is the solvent it forms an aqueous solution

35. __________________________________________________________________
Notes, p4: The pH Scale
measures the concentration of hydrogen ions (H+) in an aqueous solution.
It ranges from 0 to 14.
Neutral
__________________________________________________________________
0 Acids Bases 14

36. Acids have more H+ than pure H2O
Acids measure less than 7 on the pH scale
Examples:
HCl (hydrochloric acid)
Vinegar (acetic acid)
Lemon juice (citric acid)

37. Bases have less H+ than pure H2O
pH value is alwaysgreater than 7
Examples:
NaOH (sodium hydroxide)
KOH (potassium hydroxide)
NH3 (ammonia)

38. Neutral Substances have a pH = 7

40. Buffers…
Causes a solution to resist change in pH by adding or removing H+’s
Many biological fluids contain buffers!! Why??

41. 4.4 Indicators…
Chemicals that turn different colors in different pH values
Bromothymol Blue, Phenolphthalein, pH paper
Turn to page 8 of your packet