Chemistry Praxis
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53 terms
Terms | Definitions |
|---|---|
 mass | the quantity of matter in a material |
| matter | whatever occupies space and can be perceived by our senses |
| Law of conservation of mass | total mass remains constant during a chemical change/reaction ( demonstrated by Antoine Lavioisier) |
| Physical change | change in the form of matter, but not its chemical identity |
| Chemical Reaction | a change in which one or more kinds of matter are transformed into a kind of matter or several kinds of matter |
| Physical property | characteristic that can be observed for a material without changing its chemical identity |
| Chemical property | a characteristic of a material involving its chemical change |
| substance | cannot be separated into other kinds of matter by any physical means |
| Element | a substance that cannot be decomposed by any chemical reaction into simpler substances |
| Compounds | 2+ elements chemically combined in definite proportions |
| Law of definite proportions | a pure compound always contains constant proportions of the elements by mass |
| mixtures | material that can be separated by physical mean into two or more substances.Non-fixed proportions |
| heterogeneous mixture | has physically distinct parts, each with different properties |
| homogenous mixture | is uniform in its properties throughout given samples |
| phase | one of several different homogenous materials present in the portion of matter under study |
| chromatography | separation technique, depends on speed of substance moving past a stationary phase to which it may be attracted through a gas or liquid phase |
| precision | the closeness of a set of values obtained from identical measurements of a quantity |
| accuracy | the closeness of a single measurement to its true value |
| Significant figures rules | 1. all digits are significant except zeros at the beginning of the number 2. terminal zeros at the right of decimal are significant 3.multiplication/division:least # of sig figs 4.addition/subtraction: least # of decimal places |
| angstrom | 10^-10 m |
| kilogram | 2.2 lbs |
| density | mass/volume |
| Dalton's atomic theory | 1.all matter is composed of indivisible atoms 2. an element is a type of matter composed of only one kind of atom 3. a compound is a type of matter composed of atoms of two or more elements chemically combined in two or more elements chemically combined in fixed proportions 4. a chemical reaction consists of the rearrangement of the atoms present in the reacting substances to give new chemical combinations present in the substances formed by the reaction |
| Law of multiple proportions | in a compound the mass ratios of the elements are in small whole numbers |
| JJ Thomson (1897) | *atoms not indivisible -cathode ray tube, ratio of mass of electron and charge of electron |
| Robert Millikan (1909) | *obtained the charge of electron (1.602x10^-19 coulombs) -oil drop experiment |
| Ernest Rutherford (1911) | -nuclear model of the atom -gold foil experiment -alpha rays through gold foil |
| atomic number (z) | number of protons, subscript |
| James Chadwick (1932) | -alpha-particle scattering experiments -the ray is neutrons |
| mass number (A) | protons and neutrons, superscript |
| nuclide | atom with a definite atomic number and mass number |
| isotopes | same number of protons, various neutrons |
| Atomic mass units (amu) | -Carbon-12 mass scale -mass spectrometer -1 amu=1/12 the mass of Carbon-12 |
| atomic weight | average atomic mass for the naturally occurring element (amu) |
| fractional abundance | the fraction of the total number of atoms that is composed of a particular isotope |
| Dimitri Mendeleev (1869) & J.Lothar Meyer | -arrange elements by atomic weight by properties -horizontal rows & vertical **periodic table |
| Alkali Metals (IA) | -soft metals -react easily with water |
| Halogens (VIIA) | very reactive |
| metal | has a luster/shine, good conduction of heat and electricity, malleable and ductile |
| nonmetal | does not exhibit the characteristics of a metal, most are gases or solids |
| metalloid | both metallic and nonmetallic properties, semiconductors |
| chemical formula | chemical symbol and subscripts |
| molecule | covalently bonded elements |
| polymers | large molecules of smaller repeating molecules |
| monomers | smaller repeating molecules |
| formula unit | group of atoms int he formula |
| organic compounds | C and other elements |
| Hydrocarbons | only H and C |
| functional group | reactive portion of a molecule that undergoes predictable reactions |
| chemical nomenclature | naming chemicals |
| inorganic compounds | no carbon |
| monatomic ions | one atom forms anion, charges associated with period |
| polyatomic ion | 2+ atoms chemically bonded with a net charge |
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