Why Study Chemistry in Biology?

I. The Atom A. Definition: smallest particle of an element

B. Composition Subatomic Particle ChargeMassLocation Proton+11Nucleus Neutron01Nucleus Electron1/1840 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: H 2 O, 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: H 2 O

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 bonds slightly 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-inch paperclip over-filled water 3oz Dixie cup

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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 o C / 212 o F

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 o C or 32 o F

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 opposite ICE 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