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Some slides adapted from Burlingame HS the systematic investigation of nature neither it depends on how it is used (based on your values) to make intelligent decisions one must know the facts & consider the risks and benefits. the study of the composition of substances & the changes they undergo the study of the structure & properties of matter Synthesizing new materials Inventing new diagnostic methods for detection of disease Using bacteria to produce chemicals An observation is something that is witnessed and can be recorded. A theory is an explanation of behavior. A law is a summary of observed behavior. ◦ A law tells what happens; a theory is our attempt to explain why it happens. Every laboratory investigation involves gathering and recording data and observations. Quantitative: information that involves a measurement of any kind. Any value recorded directly from a tool is considered quantitative data. It should always be recorded immediately, along with its units of measure. Qualitative: information that is observed using your senses, instead of a tool like a measuring stick. This includes such descriptions as color as well as observations about texture changes and smell. ex. fever: touch/thermometer Quantitative Expressed as a quantity. Contains a number or quantity. Mr. Burton is 4 ft tall. Ms. Dee is 69 yrs old. Mr. Franck runs 8.5 miles a day. Qualitative Of, relating to quality. Does not contain a number or quantity. Mr. Burton is short. Ms. Dee is really old. Mr. Franck runs a lot. Scientific laws describe things. They do not explain them. ◦ Isaac Newton knew what gravity did (he could describe its behavior), but he could not explain why gravity did it. ◦ Newton's Law of Gravity: Each object in the universe attracts each other body. Theories inevitably change as more information becomes available. Ex. The motions of the sun and stars have remained virtually the same over the thousands of years during which humans have been observing them, but our explanations - our theories- have changed greatly since ancient times. A theory is only an interpretation or a possible explanation of why nature behaves in a particular way. Anything that has mass and takes up space. All matter is made up of tiny particles called atoms. Elements - basic unit of matter Compound - made of 2 or more atoms combined These are classified as: Substances definite composition, pure uniform throughout (Homogeneous) definite melting/boiling point Heterogeneous Mixture – contains regions that have different properties from those of other regions. ◦ nonuniform Homogeneous Mixture – all regions of the mixture have the same properties and same concentration of salt and water. ◦ uniform; a solution These are classified as mixtures because they have: variable composition physically separable (distallation) no definite melting/boiling point Farm fresh milk ◦ Heterogeneous Homogenized milk ◦ Homogeneous Gasoline ◦ Homogeneous The ocean ◦ Heterogeneous Oil and vinegar salad dressing ◦ Heterogeneous Maple syrup ◦ Homogeneous consists of a solute and solvent (ex: saltwater, air, glass, alloys) Solid definite shape & volume locked into position & close together vibrates about a fixed point Liquid definite volume assumes shape of container vibrates about a moving point flows Gas assumes shape & volume of container easily compressed & expands without limit vs. vapor Plasma high energy particles found in stars produces auroras Physical • Are properties of an element or compound that can be observed without a chemical reaction of the substance. • Ex. length, color, temp., density • extensive -amount of matter (mass, length,…) • intensive -nature of material (density, malleability, ....) Chemical • Are properties of an element or compound in chemical reactions. • reaction, burning, ... Water boils@100°C. ◦ Physical Property Diamonds cut glass. ◦ Physical Property Water can be separated by electrolysis into H & O. ◦ Chemical Property Sugar is dissolved in water. ◦ Physical Property Vinegar reacts with baking soda. ◦ Chemical Property Yeast acts on sugar to form carbon dioxide and ethanol. ◦ Chemical Property Aluminum has a low density. ◦ Physical Property Physical change phase, size, shape still has same properties as before Chemical change in substance, (reaction, burning) new substance with different properties Dry ice, solid carbon dioxide, is sublimed at 25°C ◦ Physical Change Salt is dissolved in water. ◦ Physical Change Iron rusts in a damp environment. ◦ Chemical Change Gasoline burns in oxygen. ◦ Chemical Change Hydrogen peroxide decomposes to water and oxygen. ◦ Chemical Change Law that states … ex. Think of cutting a piece of aluminum foil into smaller and smaller pieces. How far can it be cut? ◦ smallest particle of an element that retains its properties ◦ are very tiny particles that form the building blocks for all matter. ◦ Each element is made up of only one kind of atom. Elements - Substances that contain only one type of atom. Graphite and diamond are both elemental carbon ◦ For example, pure aluminum contains only aluminum atoms elemental copper There are 118 (book: 115) known elements; 93 (book 88) occur naturally on earth. The 25 elements not found on earth are derived artificially All artificially derived elements are radioactive with short half-lives. Many element names and symbols have Greek & Latin roots. Many of the more recently discovered elements are named after countries or famous scientists. Compound - substances made by bonding atoms together in specific ways. Theses substances contain two or more different types of atoms Plastic = C31H24N4O4 Glucose = C6H12O6 If you enlarge the proton to the size of a golf ball the electrons travel in a cloud that is 2 miles in diameter. There are 6.5 x 1021 (septillion) atoms in a drop of water. That’s 6,500,000,000,000,000 ,000,000 atoms in one drop! ◦ no can be divided into: ? fundamental building blocks of all atoms ◦ PROTON: Symbol: (p+ Charge: (+1) Location: nucleus atomic mass: 1.00 u ◦ NEUTRON: Symbol: (n) Charge: (0) Location: nucleus atomic mass: 1.00 u ◦ ELECTRON: Symbol: (e-) Charge: (-1) Location: electron cloud atomic mass: 1/1837 u An electron is 0.0001 times the mass of a proton. It is generally considered to have no mass. ◦ Nucleus: small dense core, contains nearly all the mass and has a (+) charge contains the protons and the neutrons ◦ Electron Cloud: the “empty space” of the atom, contains the electrons and so has a (-) charge ◦ Atomic Number (Z) equals # of protons in nucleus (NEVER changes) discovered by Moseley Z = # of e- in a neutral atom (+ = -) ◦ Mass Number (A) measurement in amu 1 amu = 1/12 mass of a C atom Mass Number = number of protons + number of neutrons A=p+n OR # of n = A – Z ALWAYS a whole number Protons = Atomic Number Electrons = Atomic Number for a neutral atom Neutrons = Mass number Atomic Number Sample 1 31 P 15 How many protons are there in the nucleus of a phosphorus atom? How many electrons does a neutral atom of phosphorus have? How many neutrons are there in the nucleus of a phosphorus atom? 40 Ca 20 How many protons are there in the nucleus of a calcium atom? How many electrons does a neutral atom of calcium have? How many neutrons are there in the nucleus of a calcium atom? Two or more forms of atoms of the same element with different masses. Atoms contain the same number of protons but different numbers of neutrons. ◦ Example: ◦ Boron-10 (10B) has 5 protons and 5 neutrons ◦ Boron-11 (11B) has 5 protons and 6 neutrons 10B 11B All atoms of an element have the same atomic number and therefore the same number of protons. However, for many elements, the number of neutrons can vary. Isotopes are atoms of the same element with different numbers of neutrons. # Neutrons = Mass Number - # Protons 12 6 C 6 protons 12 - 6 = 6 6 neutrons 13 6 C 6 protons 13 - 6 = 7 7 neutron 14 6 C 6 protons 14 - 6 = 8 8 neutrons Both isotopes have only 1 proton. Tritium has 2 neutrons that are not present in the stable form of hydrogen. The mass of an element depends on both the mass and the relative abundance of each element’s isotopes. The average atomic mass of an element is found by multiplying the atomic mass of each isotope by its relative abundance (expressed in decimal form) and adding the results. This is why the atomic mass found on the periodic table is often not a whole number. Average Atomic Mass = (rel. abund.) x (iso. mass) + (rel. abund.) x (iso. mass) + (rel. abund.) x (iso. mass) + ….. average of all isotopes of an element Cl-35; actual mass: 34.9689 u @ 75.771% Cl-37; actual mass: 36.9659 u @ 24.229% Calculate: (34.9689 u) x (75.771%) = (36.9659 u) x (24.229%) = + 26.496 u 8.9565 u 35.453 u What Mg? is the average atomic Mass of ◦ Mg-26 11.01% ◦ Mg-25 10.00% ◦ Mg-24 78.99% Average Atomic Mass = (0.7899 x 24) + (0.1000 x 25) + (0.1101 x 26) = 24.32 amu Names of the following groups: IA: Alkali Metal IIA: Alkaline Earth Metal IIIB-IIB: Transition Metal VIA: Chalcogen VIIA: Halogen VIIIA: Noble Gases Inner Transition Metal conduct electricity/heat, malleable, lustrous, ductile, tenacious, lose electrons (+ #’s), high melting point, left of line Insulators, nonmalleable, dull, non-ductile, brittle, low melting point, gain electrons (#’s), right of line properties of both follows zig-zag line (except Al) molecules made of 2 atoms ex. H2, O2, N2, F2, I2, Cl2, Br2 Hydrogen gas, oxygen gas, ….. atom with a charge atoms gain or lose electrons to become stable gaining results in a negative (-) charge; more electrons than protons losing results in a positive (+) charge; more protons than electrons The Lithium Atom (Li) has 3 protons and 3 electrons. The Lithium Ion (Li+) has 3 protons and only 2 electrons. The Fluorine atom (F) has 9 protons and 9 electrons. The Fluorine ion (F-) has 9 protons and 10 electrons. Magnesium Atom (Mg) ◦ 12 protons ◦ 12 electrons ◦ No Charge The Magnesium Ion(Mg+2) ◦ 12 protons ◦ 10 electrons ◦ +2 charge ◦ 1st Atomic Theory: Democritus atomos: indivisible ◦ Dalton’s Atomic Theory All matter is composed of atoms All atoms of same element are identical and atoms of different elements are not identical Atoms unite in simple ratios to form compounds Reactions occur when atoms are joined, separated or rearranged, but a reaction can not change 1 atom into another “solid sphere” ◦ J.J. Thomson: used a cathode ray tube to discover electrons cathode ray: collection of very small negatively charged particles moving at high speeds (ex. TV picture tube) J.J. Thomson: used a cathode-ray tube to discover electrons Streams of negatively charged particles were found to emanate from cathode tubes. ex. TV picture tube J. J. Thompson is credited with the discovery of electrons (1897). ◦ Thomson “Plum-pudding model” ◦ E. Rutherford discovered the nucleus (positively charged) Demo-chain-linked fence Ernest Rutherford shot particles at a thin sheet of gold foil and observed the pattern of scatter of the particles. Since some particles were deflected at large angles, Thompson’s model could not be correct. Rutherford postulated a very small, dense nucleus with the electrons around the outside of the atom. Most of the volume of the atom is empty space. ◦ Rutherford “Donut model“ ◦ Bohr “Planetary Model“ ◦ J. Chadwick discovered the neutron