Chemistry Chapters 2 and 3

Ex: Number of e-s or neutrons Properties of Matter Physical – observed and measured without permanently changing identity of matter Ex: mass and volume Chemical – describe a substance’s ability to change into a new substance (i.e., chemical change) Ex: Number of e-s or neutrons

Phases of Matter (physical properties) Gas Liquid Solid

Composition of matter Atoms – smallest structures of matter that are unable to be broken down further and maintain their properties Protons: + ; weigh 1 AMU Neutrons: 0 ; weigh 1 AMU Electrons: – ; weigh 1/1836 AMU E levels differ with number of electrons present

Atomic number and mass The atomic number is … The atomic mass # is … # of protons in atom The atomic mass # is … # of protons AND neutrons

Chemical elements Over 100 elements (90 found in nature; the rest have been created in the lab) Isotopes – atoms with extra neutrons. What does that mean for the atom? How can you determine if an element is an isotope? Ion – atom or molecule with + or – e-s

Electrons e-s are found in E levels or shells More E = higher E level Less E = lower E level Valence = outer E level Octet rule – atoms like having 8 e-s in their valence shell (2 for H)

Interactions of Matter In order to achieve stability, an atom will either gain, lose, or share e-s, which will change the physical and chemical characteristics Ionic Bonds – transfer of e-s

Interactions of Matter Covalent Bonds – sharing e-s; can be single, double, or triple bonds

Interactions of Matter Polar Covalent Bonds – unequal sharing of e-s

Interactions of Matter H-bonds and Van der Waals – interaction between slight charges

Water The most important property of the water molecule is that it is slightly charged on each end due to an uneven distribution of e-s + -

Water Cohesion – force attracting water molecules to each other. Causes surface tension, which is why this lizard can “run” on water

Water Adhesion – water molecules attracted to other slightly charged molecules Capillarity – combination of the other two forces which causes the movement of water upward through tube cells Transpiration pull

Water A solution is a substance that is uniformly spread throughout; with or without a chemical change. Solvent – substance that does the dissolving Solute – what is to be dissolved Examples: Sugar and water Tea, coffee

Example of Importance to Life Properties of Water Property Example of Importance to Life Cohesion Water flows, forming habitats and a matrix for biological molecules High (specific) heat capacity (1g, 1OC) Water regulates constant internal body temperature High heat of vaporization (1g to gas) Evaporation (evaporative cooling – sweating) Adhesion Water acts as a solvent Solid less dense than liquid Keeps ponds and lakes liquid

Dissociation of Water Water can dissociate into the hydrogen and hydroxide ions H2O  H+ + OH-

Water Acids – Compounds that release H+ ions (much like how NaCl dissociates in water but H+ are one of the most reactive ions on the planet) Bases – Compounds that release OH- (is the opposite of an acid; the OH- are as reactive as H+) Combining an acid and a base produces water and a salt

The more H+ present, the lower the pH # The more OH- present the higher the pH #