Biology Ch. 2

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Biology Ch. 2
2011-09-17 10:33:43

Biology Concepts & Connections
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  1. Matter
    Anything that occupies space and has mass.
  2. Element
    A substance that cannot be broken down to other substances by ordinary chemical means.
  3. Compound
    A substance consisting of two or more different elements combined in a fixed ratio.
  4. Trace Elements
    An element that is essential for life but required in extremely minute amounts.
  5. Atom
    The smallest unit of matter taht still retains the properties of an element.
  6. Proton
    A subatomic particle with a single positive electrical charge.
  7. Electron
    A subatmoic particle with a single negative charge.
  8. Neutron
    A subatomic particle that is electrically neutral (no charge).
  9. Nucleus
    An atom's central core, containing protons and neutrons. The genetic control center of a eukaryotic cell.
  10. Atomic Number
    The number of protons in each atom of a particular element.
  11. Mass Number
    The sum of the number of protons and neutrons in its nucleus.
  12. Atomic Mass
    The total mass of an atom; also called atomic weight. Given as a whole number, the atomic mass approximately equals the mass number.
  13. Isotpes
    One of several atomic forms of an element, each with the same number of protons but a different number of neutrons.
  14. Radioactive Isotope
    An isotope whose nucleus decays spontaneously, giving off particles and energy.
  15. Electron Shell
    An energy level representing the distance of an electron from the nucleus of an atom.
  16. Chemical Bonds
    An attraction between two atoms resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells.
  17. Covalent Bond
    The strongest kind of chemical bond.
  18. Electronegativity
    The attrations of a gven atom for the electrons of a covalent bond.
  19. Nonpolar Covelent Bonds
    A covelent bond in which electrons are shared equally between two atoms of similar electronegativity.
  20. Polar Covalent Bonds
    A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.
  21. Polar Molecule
    A molecule containing polar covalent bonds and having an unequal distribution of charges.
  22. Ion
    An atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons.
  23. Ionic Bond
    A chemical bond resulting from the attraction between oppositely charged ions.
  24. Salt
    A compound resulting from the formation of ionic bonds; also called an ionic compound.
  25. 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 (or in another region of the same molecule.)
  26. Chemical Reaction
    The making and breaking of chemical bonds, leading to changes in the composition of matter.
  27. Reactants
    A starting material in a chemical reaction.
  28. Product
    An ending material in a chemical reaction.
  29. Cohesion
    The sticking together of molecules of the same kind, often by hydrogen onds.
  30. Adhesion
    The attraction between different kinds of molecules.
  31. Surface Tension
    A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules.
  32. Heat
    The amount of energy associated with the movement of atoms and molecules in a body of matter.
  33. Temperature
    A measure of the intensity of heat in degrees, reflecting the average kinetic energy or speed of molecules.
  34. Evaporative Cooling
    The process in which the surface of an object becomes cooler during evaporation.
  35. Solution
    A liquid that is a homogeneous mixture of two or more substancs.
  36. Solvent
    The dissolving agent of a solution. Water is the most versatile solvent known.
  37. Solute
    A substance that is dissolved in a solution.
  38. Aqueous Solution
    A solution in which water is the solvent.
  39. Acid
    A substance that increases the hydrogen ion concentration in a solution.
  40. Base
    A substance that decreases the hydrogen ion concenration in a solution.
  41. pH Scale
    A measure of teh relative acidit of a solution, ranging in value from 0 (most acidic) to 14 (most basic). The letters pH stand for potential hydrogen and refer to the concentration of hydrogen ions.
  42. Buffers
    A chemical substance that resists changes in pH by accepting hydrogen ions from or donating hydrogen ions to solutions.
  43. Acid Precipitation
    Rain, snow, or fog that is more acidic that pH 5.2.
  44. Ocean Acidification
    Decreasing pH of ocean waters due to absorption of excess atmospheric CO2 from the burning of fossil fuels.