Biology 201, Chapter 2
Biology 201, Chapter 2 BIOL 201-015
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This 3 page Class Notes was uploaded by Kayla Wisotzkey on Sunday September 11, 2016. The Class Notes belongs to BIOL 201-015 at Towson University taught by Cheryl D. Warren in Fall 2016. Since its upload, it has received 73 views. For similar materials see Intro to Cell Biol & Genetics in Biology at Towson University.
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Date Created: 09/11/16
Kayla Wisotzkey Chapter 2 The Nature of Molecules and the Properties of Water Subatomic particles Matter: has mass and occupies space, is composed of atoms Nucleus: contains protons (positive charge) and neutrons (no charge). Electrons(negative charge) are found in the orbitals surrounding the nucleus MOST of an atom’s volume is empty space Mass number: the number of protons PLUS the number of neutrons Atomic number: the number of protons (this identifies the element) Valence number: the number of unpaired electrons Octet rule: All atoms want to fill their outer circle with electrons (Max. 8 electrons) Electrons are attracted to the positive nucleus, so the farther away the electron is from the nucleus, the higher its potential energy is Isotopes: atoms of a single element that possess different numbers of neutrons Bonding Ion: Any atom with a charge Ionic bonds: when an atom gives away or gains an electron. These bonds form: a. cation: has a positive charge, caused by the loss of an electron b. anion: has a negative charge, caused by the gain of an electron covalent bonds: when one or more pairs of electrons are shared between 2 atoms, very STRONG bond a. single covalent bond: one pair of electrons are shared; free rotation and flexibility b. double covalent bond: two pairs of electrons are shared; more versatility, more rigid, no rotation c. triple covalent bond: three pairs of electrons are shared, extremely rigid Electronegativity: an atom’s affinity for electrons UPPER RIGHT hand side of the periodic table are more electronegative nonpolar covalent bonds: equal sharing of electrons, equal electronegativity polar covalent bonds: unequal sharing of electrons; the more electronegative atoms hold the electrons more tightly and will have a partial negative charge, and the other atom will have a partial positive charge Hydrogen bonding: covalent bond between Hydrogen and a strongly electronegative atom and another strongly electronegative atom To increase a reaction: apply heat, add more reactants, and add catalysts Water’s abilities Hydrogen bonds: Water can form hydrogen bonds, weak chemical associations that form between partially negative Oxygen atoms and partially positive Hydrogen atoms of two different water molecules Stability: water molecules are stable because they satisfy the octet rule and have no unpaired electrons, and they carry out no electrical charge Cohesion: water is attracted to itself and sticks together; this quality is responsible for water being a liquid and its surface tension Adhesion: water sticks to any substance with which it can form hydrogen bonds, causes the meniscus that occurs in graduated cylinders Capillary action: the adhesion of water to a glass surface is stronger than the force of gravity Properties of water 1) High specific heat: the amount of heat that must be absorbed or lost for one gram of that substance to change its temperature by 1C Water heats up more slowly and holds its temperature longer than any other compound 2) High heat of vaporization: the amount of energy needed to change one gram of a substance from a liquid to a gas As water changes from a liquid to a gas it requires energy to break the hydrogen bonds 3) Water is a solvent: something that dissolves other substances Solute: the substance that dissolves in the solvent (salt, sugar, etc.) Water organizes nonpolar molecules: when nonpolar molecules are placed in water, the water molecules exclude them and make them clump together Hydrophobic: nonpolar molecules, don’t bond with water, “waterfearing” Hydrophilic: polar molecules (ions), bond with water, “waterloving” 4) Water can form ions ionization: covalent bonds of a water molecule sometimes break, and a proton dissociates from the molecule. It breaks into a Hydrogen ion and a Hydroxide ion 5) Ice is less dense than water because the hydrogen bonds in ice spread the water molecules far apart; this causes water to freeze from the top down At low temperatures, water molecules are locked into a crystallike lattice of hydrogen bonds, forming ice Acids and bases acid: any substance that dissociates in water to increase the Hydrogen ion level and LOWER THE pH level base: a substance that combines with Hydrogen when dissolved in water, lowering the Hydrogen ion level and RAISING THE pH level buffer: a substance that resists changes in pH; it acts by releasing hydrogen ions when a base is added and absorbing hydrogen atoms when an acid is added…the effect is keeping the Hydrogen level constant Acidosis: human blood’s pH goes from 7.4 to 7.1, could be deadly if not treated Alkalosis: human blood’s pH goes from 7.4 to 7.7, deadly if not treated pH scale goes from 0 to 14, 0 being acidic and 14 being basic pH= log[H ]+
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