Biology

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Author:
spagem84
ID:
99366
Filename:
Biology
Updated:
2011-09-11 21:25:11
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exam
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Description:
chapter 2
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  1. What is an element?
    is a substance that cannot be broken down to other substances by ordinary chemical means.
  2. How many elements are there in nature?
    there are 92 natural elements on earth
  3. How many are essential to life?
    25 of the 92 natural elements are essential to life
  4. Which 4 make up 96% of all elements found in cells?
    Carbon (C)

    Oxygen (O)

    Nitrogen (N)

    Hydrogen (H)
  5. What is a trace element?
    an element that is essential for life but required in extremely minute amounts
  6. Define compound.
    is a substance consisting of two or more different elements combined in a fixed ratio.
  7. How do compounds demonstrate the emergent property theme?
    element to compound

    -ex: NaCl (sodium choloride)=table salt
  8. Define atom.
    smallest unit of matter that retains properties of an element
  9. Differentiate between protons, neutrons, and electrons (size, location, charge). Differentiate between atomic number and mass number.
  10. Describe an isotope and be able to recognize one.
    have the same number of protons and electons but different number of neutrons

    -pg. 20, table 2.3
  11. Describe “electron shell”.
    an energy level representing the distance of an elctron from the nucleus of an atom.

    an atom may have 1, 2, or 3 electron shells
  12. Know the maximum number of electrons that can be in the first 3 electron shells.
    the 1st electron shell has only one orbital and can hold only 2 electrons.

    the second and third rows, the outer shell has four orbitals and can hold up to 8 electrons (4 pairs)
  13. Define ion, molecule, reactant, and product.
    ion: is an atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons

    molecule: two or more atoms held together by covalent bonds

    reactant: conversion of the starting materials

    product: the material resulting from the chemical reaction
  14. Differentiate between ionic, covalent, and hydrogen bonds.
    ionic bond: 2 ions with opposite charges that attract eachother and the ions are held togeher (opposites attract)

    covalent bond: the strongest kind of chemical bond in which two atoms share one or more paris of outer-shell electrons.

    hydrogen bond: a type of weak chemical bond formed when the partially positive hydrogen atom participating in a polar covalent bond in one molecule is attracted to the partially negative atom participating in a polar covalent bond in another molecule
  15. Know the difference between nonpolar and polar covalent bonds
    nopolar covalen bond: equal pull between atoms

    polar covalent bond: unequal pull between atoms of different elements/electonegativities-polar molecules
  16. List and describe the 4 properties of water that help support life.
    1: cohesion, adhesion, surface tension

    2: resists temperature change

    3: water can exist as a gas, liquid, and solid. it is less dense as a solid due to hydrogen bonding

    4: solvent of life: solvent (the dissolving agent) and solute (the substance dissolved)
  17. Define cohesion
    the sticking together of molecules of the same kind, often by hydrogen bonds.
  18. Define adhesion
    attraction between different kinds of molecules
  19. Define surface tension
    a measure of how difficult it is to break the surface of a liquid-hydrogen bonds are responsible for surface tension (ex: bg able to float in water)
  20. Define heat
    energy associated with movement of atoms and molecules in matter
  21. Define temperature
    measures the intensity of heat
  22. Define solution
    liquid consisting of a uniform mixture of two or more substances
  23. Define solvent
    the dissolving agent of a solution
  24. Define solute
    a substanc that is dissolved in a solution
  25. Define acid, base, and buffer.
    acid: substance that increases the hydrogen ion concentration in a solution (H+) hydrogen ions

    Base: substance that increase the hydrogen ion concentration in a solution (OH-) hydroxide ions

    buffer: a chemical substanc that resists changes in pH by accepting hydrogen ions from or donating hydrogen ions to solutions.
  26. Recognize the difference between a hydrogen ion and a hydroxide ion.
    hydrogen ions are acids

    hydroxide ions are base
  27. Know how to read the pH scale (where the acids are, where the bases are, where neutral is, and how much change each pH unit represents).
    acids from 0 to 6

    7 is neutral

    base from 8 to 14

    *concentration is 10x greater each step
  28. In what pH range are most biological fluids?
    they are between 7 to 7.8

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