103 ch 2 briehn rev sp 12
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Transcript of 103 ch 2 briehn rev sp 12
Chapter 2
Remember…..
Organism
organ system
Organs
Tissues
Cells
Molecules
atoms
Matter = anything that
1. has mass
2. takes up space
3 Forms of Matter
Holds Shape
Fixed volume
Container shape
Free Surface
Fixed Volume
Container Shape
Volume of Container
Matter composed of basic substances
Elements1. Specific chemical & physical characteristics
2. Fundamental substances
3. 1 type of atom
92 naturally occurring elements
11+ Synthetic elements
Primary Elements of Living Things
1. Carbon
2. Hydrogen
3. Nitrogen
4. Oxygen
5. Phosphorus
6. Sulfur
98% 95%
Naming of Elements1. Latin or English
2. Atomic Symbol = 1 or 2 letter abbreviation
Carbon = C
Hydrogen = H
Oxygen = O
Sodium = Na
Iron = FePotassium = KNitrogen = N
Atom = smallest particle of an element
that displays properties of that element
John Dalton: Atomic Theory
Early 1800’s
“All Matter is composed of atoms”
Structure of an Atom: (Sub-atomical Particles)
Protons
Neutrons
Electrons
Sub-atomic Particles: Charges
Protons = Positive Charges
Neutrons - Neutral Charges
Nucleus
Electrons – Negative Charges
Atomic Number & Weight
Atomic number = number of protons
(# protons = # electrons)
Atomic weight (mass) = protons + neutrons in an atom.
Therefore, if…..Atomic number = number of protons
Atomic weight = protons + neutrons
Then………
atomic weight - atomic number = # of neutrons
(P + N) (# of P) (# of N)
IsotopesIsotopes = atoms of same element with:
same atomic number (# protons),
different atomic weight (# protons & neutrons)
What is different?
Isotopes1. Unstable…..
• break down
2. Give off radiation
3. Used in medicine
& dating fossils
Electron Configuration determines properties of an atom
• # of electrons = # of protons.• Electron = energy in an atom• Electrons have same weight & charge,
vary in energy content• Farthest from nucleus =
greatest “potential energy”
Atomic Energy Levels
Orbital: where electrons found.
Shells: in orbitals, found in shells
Octet RuleThe first shell: full = 2 electrons.Beyond first shell: full = 8 (or multiples) electrons
Molecule – smallest part of element or compound that has properties of that element or compound.
Compound - Two or more different types of atoms that react or bond together.
Chemical Formulas
1 Symbols for composition of substance.
ex: Hydrogen Cloride = HCl
2 More than 1 atom of same kind = subscript
ex: Water or H2O
Determining Reactivityouter (valence) shell not full = reactive
outer (valence) shell full = not reactive
(inert)
outer shell = valence shell
Atoms want a full outer shell.
To complete outer shell, an atom may:
1. Give up an electron
2. Accept an electron
3. Share an electron
chemical bond = transfer or sharing electrons with another
atom
Electrons possess energy
chemical bond = energy relationship
**Energy Relationship **
1. Energy required to form bond
2. Energy stored in chemical bonds.
3. Energy released when bond is broken.
This concept is a top priority for living organisms.
Types of Reactions
Endergonic reactions – small molecules bonded to form large molecules.
Energy is required.
Exergonic reactions – large molecules broken down into small molecules.
Energy is released.
Chemical reactions indicated by
chemical equations
2H2 + O2 2H2O reactants products
Equal # of atoms exist on both sides
Types of Reactions
• Synthesis A + B C
• Decomposition AB A + B
• Exchange AB + CD AD + CB
• Reversible A + B AB• Oxidation loss of electron (break down)
• Reduction gain of electron (synthesis)
Chemical Bonds
• Ionic
• Covalent
• Polar Covalent
• Hydrogen
Ionic Bonding =
transfer of electrons
Remember…
Atoms are electrically balanced
Electron transfer charge imbalance
creates ions (charged atom)
ionic bond = attraction of - & +
3 P +7 P +9 P +3 P + e-
e-e-
e- e-
e-
e-
e-
e-
e-e-
e-
3 P +7 P +9 P +3 P + e-
e-e-
e- e-
e-
e-
e-
e-
e-e-
e-e-e-
3 P +
3 + and 2 –NET = 1+
10 - and 9+ NET = 1-
Covalent Bonding =
sharing of electrons
1. Atoms linked like a chain.
2. Very strong bonds
(single, double, etc)
3. Found in organic molecules.
(Hydrogen, Oxygen & Carbon)
e-
e-
e-
e-
e-
e-
e-e-
e-
e-e-
e-
e-e-
e-e-
e-
e-
e-
e-
e-e-
e- e-
Polar Covalent Bonds=
Unequal sharing of electrons
• Molecule formed has both:
positive end
negative end
• “polar” molecule
• Water
hydrogen bond =
a slightly “+” hydrogen atom
attracted to
slightly “-”atom in other molecule
• Weak and easily broken
• Many together can be quite strong
• Usually the bond is with O or N
• NOT electron sharing or donating…. It is an ATTRACTION to neighboring molecule
• Illustrated by a broken dotted line.
• http://programs.northlandcollege.edu/biology/Biology1111/animations/hydrogenbonds.html
Chemical properties of water
are essential to life
Living things 70–90% water
Properties of Water• Resists changes in temperature
gains and loses heat slowly
Ocean circulation = Europe’s mild winters even though it is further north than Canada.
Properties of Water• Resists change in state tends to remain liquid high freezing point & high boiling point
Properties of Water
Universal SolventMost substances associate with water.
Facilitates chemical reactions.
solute + solvent = solution
Hydrophilic = “water” “loving”
(attracted to water molecules)
Hydrophobic = “water” “fearing”
(repelled by water molecules)
Properties of Water
• Cohesive and Adhesivemolecules stick together & to other molecules
(effective as a transport medium)
Properties of Water
• High Surface TensionSurface of water hard to break.
Basilisk Lizard
http://www.youtube.com/watch?v=KSLUwmJOo_M
Properties of Water
• Frozen water less dense than liquid water.Ice (solid water)
floats on liquid water.
Water has a slight tendency to
“fall apart” or
DISSOCIATE
OH- called hydroxide ion
H+ called hydrogen ion
(actually H30+)
Water dissociates into equal numbers of:
Others dissociate in water may release
unequal amounts of “+” or “-” ions
Acids = produces H+ ions taste sour
can be corrosive
Bases = can accept H+ ions taste bitter feel slippery
Acidity or Alkalinity
=
measure of relative amount of
H+ and OH- ions
dissolved in a solution
pH scale = indicate acidity and basicity of a solution
Scale ranges from 0 to 14 0-3 is very acidic
7 is neutral
11-14 is very basic or alkaline
Control of pH
is important to organisms!!
• Enzymes function only within a narrow pH range; usually neutral
• Buffers neutralize acids or bases in organisms to help control pH
(by taking up or releasing H+ ions)