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2013-01-22 04:02:14
Basic Chemistry ch2

ch 2 basic chemistry
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  1. What is matter?
    Anything that has mass and occupies space.

    • States of matter:
    • 1) solid - definite shape and volume (bone)
    • 2) liquid - definite volume, changeable shape (blood)
    • 3) Gas - changeable shape and volume (gas)
  2. What is energy?
    • Energy is the capacity to do work or put matter into motion. 
    • Has no mass

    • Types of energy:
    • 1) Kinetic - energy in action
    • 2) Potential - stored/inactive energy
  3. Forms of energy
    • 1) Chemical energy = stored in bods of chemical substances
    • 2) Electrical energy = results from movement of charged particles
    • 3) Mechanical energy = directly involved in moving matter
    • 4) Radiant or electromagnetic energy = exhibits wavelike properties (visible light, UV light, x-rays)
  4. Energy forms can be converted
    • energy may be converted from one form to another (i.e. from kinetic to potential energy when drawing an arrow)
    • conversion is inefficient because some energy is "lost" as heat
  5. Composition of Matter

    cannot be broken down by ordinary chemical means

    • each element has unique properties:
    • physical properties = are detectable with our senses, or are measurable
    • chemical properties = how atoms interact/bond with one another
  6. Composition of Matter

    unique building block for each element

    Atomic symbol = one or two letter chemical shorthand for each element.  Periodic table
  7. Major elements of human body
    • Oxygen (O)
    • Carbon (C)
    • Hydrogen (H)
    • Nitrogen (N)

    makes up about 96% body mass
  8. Lesser elements of human body
    • Calcium (Ca)
    • Phosphorus (P)
    • Potassium (K)
    • Sulfur (S)
    • Sodium (Na)
    • Chlorine (Cl)
    • Magnesium (Mg)
    • Iodine (I)
    • Iron (Fe)  -- atomic name based on Latin Ferum

    makes up about 3.9% body mass
  9. Trace elements of human body
    • typically part of enzymes
    • <0.01% of body mass:
    • --- Chromium (Cr)
    • --- Manganese (Mn)
    • --- Zinc (Zn)  boost immune system
  10. Atomic structure
    • determined by numbers of subatomic particles
    • Nucleus consists of neutrons and protons
  11. Atomic structure
    Neutrons = no charge.  Mass - 1 atomic mass unit (amu)

    Protons = positive charge.  Mass - 1 amu

    Electrons = negative charge.  Orbit nucleus. Equal in number to protons in atom.  1/2000 mass of a proton (0 amu)
  12. Models of atom
    • Orbital model = current model used by chemists.
    • -depicts probable regions of greatest electron density (an electron cloud)
    • -Useful for predicting chemical behavior of atoms

    • Planetary model = oversimplified, outdated model.
    • -Incorrectly depicts fixed circular electron paths
    • -useful for illustrations
    • -thought nucleus orbits

    see notes for pictures
  13. Atomic number
    number of protons in nucleus

    Periodic table of elements
  14. Identifying elements
    Atoms of different elements contain different numbers of subatomic particles

    Atomic number - # of protons in nucleus

    • Mass number - mass of the protons and neutrons
    • -mass numbers of atoms of an element are not all identical
    • -Isotopes are structural variations of elements that differ in the number of neutrons they contain

    Atomic weight - average of mass numbers of all isotopes (see notes for picture)
  15. atomic weight
    average of mass numbers of all isotopes

    --see notes for picture.
  16. Radioisotopes
    • spontaneous decay (radioactive)
    • similar chemistry to stable isotopes
    • can be detected with scanners
    • valuable tool for biological research and medicine

    • cause damage to living tissue:
    • -useful against localized cancers
    • -radon from uranium decay causes lung cancer
  17. Molecules and Compounds
    most atoms combine chemically with other atoms to form molecules and compounds

    Molecule - two or more atoms bonded together

    Compound - two or more different kids of atoms bonded together
  18. Mixtures
    • most matter exists as mixtures
    • - two or more components physically intermixed

    • Three types of mixtures:
    • 1) Solutions (salt water)
    • 2) Colloids (milk - fat globules dispersed in a watery solution)
    • 3) Suspensions (mud - sand suspended in water)
  19. Solutions
    • Homogeneous mixtures
    • usually transparent (e.g. atmospheric air or seawater)

    Solvent - present in greatest amount, usually a liquid

    • Solute(s) - present in smaller amounts. 
    • Very tiny, do not settle out or scatter light (e.g. mineral water... solvent = water; solute = CO2 - carbon dioxide)
  20. Concentration of Solutions
    Percent or parts per 100 parts

    Milligrams per deciliter (mg/dl)

    • Molarity or moles per liter (M)
    • --- 1 mole = the atomic weight of an element or molecular weight (sum of atomic weights) of a compound in grams
    • --- 1 mole of any substance contains 6.02x10^23 molecules (Avogadro's number)
  21. Colloids
    • colloids (emulsions)
    • -- heterogeneous translucent mixtures (e.g. cytosol)
    • -- large solute particles that do not settle out
    • -- undergo sol-gel transformations (e.g. gelatin)

    solute particles are larger than in a solution and scatter light; do not settle out.
  22. Suspensions
    • -- heterogeneous mixtures (e.g. blood)
    • -- large visible solutes tend to settle out

    solute particles are very large, settle out, and may scatter light.
  23. Mixtures vs. Compounds
    • Mixtures:
    • -- no chemical bonding b/w components
    • -- can be separated physically, such as by straining or filtering
    • -- heterogeneous or homogeneous

    • Compounds:
    • -- can be separated only by breaking bonds
    • -- all are homogeneous
  24. Chemical bonds
    electrons occupy up to 7 electron shells (energy levels) around nucleus

    Octet Rule = except for the 1st shell which is full w/2 electrons, atoms interact in a manner to have 8 electrons in their outermost energy level (valence shell)
  25. Chemically inert elements
    • stable and unreactive
    • outermost energy level fully occupied or contains 8 electrons.  -- see notes for picture
  26. Chemically reactive elements
    • outermost energy level not fully occupied by electrons
    • tend to gain, lose, or share electrons (form bonds) with other atoms to achieve stability -- see notes for picture
  27. Types of chemical bonds
    • Ionic
    • Covalent
    • Hydrogen
  28. Chemical bond

    Ionic Bonds
    Ions are formed by transfer of valence shell electrons b/w atoms

    • -- Anions ( - charge) have gained one or more electrons
    • -- Cations ( + charge) have lost one or more electrons

    attraction of opposite charges results in an ionic bond

    • Formation of an Ionic Bond
    • -- ionic compounds form crystals instead of individual molecules (e.g. NaCl - sodium chloride)

    -see notes for pict
  29. Chemical bond

    Covalent Bonds
    • -formed by sharing of 2 or more valence shell (outer shell) electrons
    • -allows each atom to fill its valence shell at least part of the time

    • sharing of electrons may be equal or unequal 
    • equal sharing produces electrically balance nonpolar molecules like CO2.  Carbon dioxide molecules are linear and symmetrical and nonpolar
    • Unequal sharing by atoms w/different electron-attracting abilities produces polar molecules like H2O
    • ---- atoms with 6 or 7 valence shell electrons are electronegative, e.g. oxygen
    • ---- atoms with 1 or 2 valence shell electrons are electropositive, e.g. sodium

    see notes for pictures
  30. Chemical bond

    Hydrogen Bonds
    attractive force b/w electropositive hydrogen of one molecule and an electronegative atom of another molecule

    • -- common b/w dipoles such as water
    • -- also act as intramolecular bonds, holding a large molecule in a 3-D shape

    -- a water strider can walk on a pond bc of the high surface tension of water, a result of the combined strength of its hydrogen bonds

    see notes for pictures
  31. Chemical reactions

    • - occur when chemical bonds are formed, -rearranged, or broken
    • - represented as chemical equations

    • chemical equations contain:
    • -- molecular formula for each reactant and product
    • -- relative amounts of reactants and products, which should balance

    • Examples:
    • [reactants] -->  [products]
    • H + H -------> H2 (hydrogen gas)
    • 4H + C -----> CH4 (methane)
  32. Patterns of chemical reactions
    • Synthesis (combination) reactions
    • -  A + B --> AB
    • - always involves bond formation; smaller particles are bonded together to form larger more complex molecules
    • - Anabolic

    • Decomposition reactions
    • - AB --> A + B
    • - reverse synthesis reactions
    • - involve breaking bonds; bonds are broken into larger molecules resulting in smaller less complex molecules
    • - Catabolic

    • Exchange reactions
    • - AB + C --> AC + B
    • -also called displacement reactions
    • -bonds are both make and broken
  33. Oxidation-Reduction (Redox) Reactions
    Decomposition reactions: reactions in which fuel is broken down for energy

    • also called exchange reactions bc electrons are exchanged or shared differently
    • --- electron donors lose electrons and are oxidized
    • --- electron acceptors receive electrons and become reduced
  34. Chemical Reactions
    all chemical reactions are either exergonic or endergonic

    exergonic reactions = release energy (catabolic reactions)

    endergonic reactions = products contain more potential energy than did reactants (anabolic reactions)

    • All chemical reactions are theoretically reversible
    • --- A + B --> AB........ AB---> A + B

    Chemical equilibrium occurs if neither a forward nor reverse reaction is dominant

    Many biological reactions are essentially irreversible due to energy requirements and removal of products
  35. Rate of chemical reactions
    • Rate of reaction is influenced by:
    • - increase temp --> increase rate
    • - decrease particle size --> increase rate
    • - increase concentration of reaction --> increase rate

    • Catalysts:  increase rate w/o being chemically changed
    • -- enzymes are biological catalysts
  36. factors influencing the rate of chemical reactions
    • chemical reactions only occur when particles collide and valence shell electrons interact
    • the smaller the reacting particles, the greater their kinetic energy and the faster the reaction rate

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