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Why Study Chemist ry in Biology?
I. The Atom
A. Definition: smallest particle of an element
B. CompositionSubatomic
ParticleCharge Mass Location
Proton +1 1 Nucleus
Neutron 0 1 Nucleus
Electron -1 1/1840 the mass of a
proton
Orbiting nucleus
Location of Electrons
Valence electrons: outermost electrons, participate in BONDING
II. Elements
A. Definition: substance that cannot be broken down into other substances
B. Biologically important elements i. Major: C H O N P S
ii. Minor: Ca Fe Mg I Se P K Na Cl
A. Compound definition: a substance containing two or more elements in a fixed ratio
– Ex: H2O, NaCl
III. Chemical Compounds
• Atoms want to fill their outer energy levels to be
• To do this, they will meet up with other atoms and either or
electrons
i. Atoms share electrons so that both atoms fill their outer energy level
Examples of covalent molecules
ii. Ionic Bonds: gimme’ that electron!• Atoms transfer electrons, becoming (+) or (-)
charged• This attraction brings them together
– Ex: Na and Cl
iii. Molecules definition: two or more atoms held together by COVALENT bonds
LIFE DEPENDS ON THE UNIQUE PROPERITIES OF WATER
V. WATER
Questions to think about
• Why do put salt on the roads? • Why do we add salt to a pot of pasta
water? • At a higher altitude why must we
cook “boil” something longer?
A. Human Composition: Cells are 70–90% water
B. Plant Composition
As much as 95% plants can be made of water
C. Formula:H2O
D. Bonds: i. Hydrogen bonds: the slightly (+) H atoms are attracted to nearby (-) O atoms, and develop a weak bond.
Hydrogen Bonds
• Hydrogen Bonds- weak bondsslightly positive H is attracted to the slightly negative O of another water molecule
E. Polarity
• Polar molecule: molecule in which opposite ends have opposite electric charges
• Why? Water is a polar molecule: because Oxygen holds electrons closer
The polar nature of water and the effects of hydrogen bonding explain most of water's unique properties.
• Cohesion • Adhesion• Solubility • Temperature moderation• The lower density of ice
i. Cohesion 1. Definition: Water “sticks” to each other Ex.: Surface tension
1-inchpaperclip
over-filled water
3oz Dixie cup
ii. Adhesion
1. Definition: Water molecules are also attracted to certain other molecules.
2. Ex. In trees/plants water goes against gravity
Called capillary action
iii. Temperature and Water
• When you heat molecules move faster
• When you cool molecules move slower
• Water takes more energy to heat because energy must break hydrogen bonds
Boiling Point: 100 oC / 212 oF
Does water boil faster if you add salt to it?
• Water Boils when it has enough energy for the molecules to leave
Freezing Point
• What would happen if our oceans did not have salt in them?
• Why do we put salt on our roads?
• Why at effect does salt have on FREEZING POINT?
0 oC or 32 oF
LOW DENSITY OF ICE• Density- amount of matter
in a volume
• In most substances the solid state is more dense than the liquid state
• Water is the oppositeICE IS LESS DENSE THAN WATER and will FLOAT
LOW DENSITY OF ICE
• WHY?• Hydrogen
bonds in ice (solid) keep molecules spaced out
LOW DENSITY OF ICE
• Floats • Ice insulates the
liquid water below allowing life to persist
