Chem 111 Ch. 1
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| 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
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| qualitative data | general observations about the system (the part of the universe that is under investigation)
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| quantitative data | numbers obtained by various measurements of the system (the part of the universe that is under investigation)
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| hypothesis | a tentative explanation for a set of observations
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| 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)
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| theory | a unifying principle that explains a body of facts and/or those laws that are based on them
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| matter | anything that occupies space and has mass
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| chemistry | the study of matter and the changes it undergoes
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| 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
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| mixture | a combination of two or more substances in which the substances retain their distinct identities (air, soft drinks, milk, cement, i.e.)
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| homogeneous mixture | the composition of the mixture is the same throughout the solution (spoonful of sugar dissolved in water after sufficient stirring)
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| 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)
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| element | a substance that cannot be separated into simpler substances by chemical means
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| 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
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| 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)
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| 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)
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| extensive property | depends on how much matter is being considered (mass, length, and volume; more matter = more mass)
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| 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)
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| macroscopic properties | can be determined directly (length, volume, mass, etc.)
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| microscopic properties | on the atomic or molecular scale, must be determined by an indirect method (chemical composition, i.e.)
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| 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
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| mass | measure of the quantity of matter of an object
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| weight | the force that gravity exerts on an object
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| 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
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| kelvin | the absolute temperature scale (0 K is the lowest temperature - there are no neg. values on this scale)
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| 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)
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| 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.
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| 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
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| 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)
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| 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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