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CHEM CH. 1
Chem 111 Ch. 1
| Question | Answer |
|---|---|
| scientific method | 1. carefully define the problem; 2. perform experiments, make careful observations, and record information about the system (data); 3. interpretation - attempt to explain the observed phenomenon; observation --> representation --> interpretation |
| qualitative data | general observations about the system (the part of the universe that is under investigation) |
| quantitative data | numbers obtained by various measurements of the system (the part of the universe that is under investigation) |
| hypothesis | a tentative explanation for a set of observations |
| law | a concise verbal or mathematical statement of a relationship between phenomena that is always the same under the same conditions (Newton's second law of motion, i.e. F=ma) |
| theory | a unifying principle that explains a body of facts and/or those laws that are based on them |
| matter | anything that occupies space and has mass |
| chemistry | the study of matter and the changes it undergoes |
| substance | matter that has a definite or constant composition and distinct properties (water, table salt-sodium chloride, carbon dioxide, i.e.); can be either an element or a compound |
| mixture | a combination of two or more substances in which the substances retain their distinct identities (air, soft drinks, milk, cement, i.e.) |
| homogeneous mixture | the composition of the mixture is the same throughout the solution (spoonful of sugar dissolved in water after sufficient stirring) |
| heterogeneous mixture | the composition of the mixture is not uniform (sand grains mixed with iron fillings - grains/fillings remain visible and separate; oil & water - the liquid doesn't have a constant composition) |
| element | a substance that cannot be separated into simpler substances by chemical means |
| compound | a substance composed of two or more elements chemically united in fixed proportions (water, i.e. is made up of 2 parts hydrogen and 1 part oxygen no matter where it comes from);can only be separated by chemical means into their pure components |
| physical property | can be measured and observed without changing the composition or identity of a substance (melting point measured when ice melts into water - differ only in appearance and not composition) |
| chemical property | any property of a substance that cannot be studied without converting the substance into some other substance (hydrogen gas forms water when it burns in air - chemical property of hydrogen; hard-boil an egg - changes chemical makeup as well as physical) |
| extensive property | depends on how much matter is being considered (mass, length, and volume; more matter = more mass) |
| intensive property | does not depend on the amount of matter being considered (temperature - two beakers of water at same room temp: if combined, temperature will not change) |
| macroscopic properties | can be determined directly (length, volume, mass, etc.) |
| microscopic properties | on the atomic or molecular scale, must be determined by an indirect method (chemical composition, i.e.) |
| tera-; giga-; mega-; kilo-; deci-; centi-; milli-; micro-; nano-; pico- | (T) 1 x 10^12; (G) 1 x 10^9; (M) 1 x 10^6; (k) 1 x 10^3; (d) 1 x 10^-1; (c) 1 x 10^-2; (m) 1 x 10^-3; (ยต) 1 x 10^-6; (n) 1 x 10^-9; (p) 1 x 10^-12 |
| mass | measure of the quantity of matter of an object |
| weight | the force that gravity exerts on an object |
| density | mass/volume (g/cm^3)*intensive property - does not depend on the quantity of matter present because it's a ratio of the two quantities |
| kelvin | the absolute temperature scale (0 K is the lowest temperature - there are no neg. values on this scale) |
| scientific notation: addition/subtraction & multiplication/division | N x 10^n - addition/subtraction: n1 must = n2. then add/subtract N1 & N2. n remains the same and equal; multiplication/division: multiply/divide N1 & N2 as usual, either add/subtract n1 & n2 (for multiplying/dividing, respectively) |
| significant figures | 1. any digit that is not zero is significant; 2. zeros btw. nonzero digits are significant; 3. zeros to the left of the first nonzero digit are not significant (.0000345 = 3 s.f.); 4. if a number is > 1, the zeros to the right of the decimal are sig. |
| sig figs: addition/subtraction & multiplication/division | addition/subtraction: only pay attention to the #'s to the right of the decimal - 25.01 + 2.1 = 27.1 NOT 27.11; multiplication/division: go by lowest # of sig figs in original - 25.55 / 2.0 = 6.3 NOT 6.275 |
| accuracy | tells us how close a measurement is to the true value of the quantity that was measured (average may give a high accuracy, so must look at precision, too) |
| precision | refers to how closely two or more measurements of the same quantity agree with one another (think of a dart board) |
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court52
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