Transcript Biology 105
Chapter 2: Atoms and Molecules Pages 26-42 Student Outcomes Name the principal chemical elements in living things and their important functions. Compare and contrast the physical properties and locations of an atom. Distinguish among chemical formulas of a substance. Student Outcomes Explain how hydrogen bonds between adjacent water molecules govern many of the properties of water. Distinguish between the terms oxidation and reduction, relating these processes to the transfer of energy. Contrast acids and bases and the pH scale. Compounds Inorganic Organic-carbon based Common elements of life Carbon Hydrogen Oxygen Nitrogen Additional lesser elements (calcium, potassium, etc) found on page 27 Elements of Earth’s Crust Top ten of abundance Oxygen Silicon Aluminum Iron Calcium Sodium Magnesium Potassium Titanium Hydrogen Elements Atom - smallest portion of an element that retains its chemical properties Electron - negative charge Proton - in nucleus, positive charge Neutron - in nucleus, neutral charge Element Properties Chemical symbol C – Carbon 0 – Oxygen Na-??? Atomic number Atomic mass Isotopes Isotopes Differ in the number of neutrons, can be interchangeable Radioactive decay can be used to measure age of a sample (1/2 life) Carbon 14 Electrons Orbitals Electron shells and valence shells Atoms are most stable when valence shell is filled Chemical Formulas Molecule Compound Molecular - Water: H20 Structural - Water: H--0--H Molecular Mass - Molecular Mass Find the mass of the following molecules: H20 02 C02 CH4 NH3 H2CO3 - (Carbonic acid) C6H1206 Chemical Equations Reactants and Products H20 + CO2 + light -> C6H1206 + 02 Chemical Bonds Covalent-sharing of electrons to fill outer shell Single Double Triple Chemical Bonds Ionic Cations and anions An ionic bond - forms as a result of the attraction between positive (cation) and negative (anion) charges NaCl - Na+ Cl- Compounds of Ionic bonds can separate in water (solvent/solute) Hydrogen Bonds Bond between Hydrogen and another atom. Very common and important bond in organisms Type of covalent bond Hydrogen end will inherit a positive charge, the other end - a negative charge. These Hydrogen bonds are weak individually, but strong in large numbers Electronegativity Measure of an atom’s attraction for electrons in chemical bonds Nonpolar - 02, CH4, H2 Polar – water (one end slightly +, one slightly-) Redox Reactions Oxidation - atom or molecule loses electrons Reduction - atom or molecule gains electrons Water molecules Cohesion - attraction of water molecules to each other Adhesions - attraction of water molecules to other molecules Capillary acton - tendency of water molecules to move against gravity when in narrow tubes Surface tension - water can ‘bulge’ over the edge Hydrophillic vs hydrophobic Makes an excellent solvent (dissolves others) Water Calorie (cal) - the heat energy required to raise the temp. of 1 g of water 1 deg C. This is known as its specific heat. Solid form is less dense than liquid form Water is most dense at 4˙C pH • The degree of a solution’s acidity. • Neutral solution • Acidic solution-proton donor • Basic solution-proton acceptor • Hydrogen(H+) vs hydroxide (OH-) ions • Buffers help maintain a neutral solution