Measurements and Calculations – Flashcards
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Quantitative
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Numerical information/data
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Qualitative
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Descriptive information/data, usually gathered by the five senses.
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Systems
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a system is a specific portion of matter in a given region of space that has been selected for study during an experiment or observation
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Hypothesis
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testable statement. serves as a basis for making prediction and for carrying out further experiments
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controls
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experimental conditions that remain constant
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variable
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any condition that changes, usually due to effects of the variable
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model
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more than a physical object' it is often an explanation of how phenomena occur and how data or events are related. models may be visual, verbal, or mathematical.
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theory
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if a model explains many phenomena successfully, it may become part of a theory, or a broad generalization that explains a body of facts or phenomena.
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quantity
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something that has magnitude, size, or amount
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measurements
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numbers with a unit; units of measurements
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SI
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standardized units eliminated confusion
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SI Base Units
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Length l (meter) , Mass m (grams), Time t (seconds), Temperature T (kelvin) , Amount of substance n (mol), Electric current I (ampere), Luminous Intensity Iv (candela)
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weight
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weight is a measure of the gravitational pull on matter, depends on gravity.
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derived units
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combinations of SI base units
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area
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square meter = length x width
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Volume
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cubic meter = length x width x mass
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Density
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kilograms per cubic meter = mass/volume
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molar mass
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kilograms per mole = mass/amount of substance
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molar volume
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cubic meters per mole = volume/amount of substance
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energy
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joule = force x length
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volume
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is the amount of space occupied by an object derived SI unit = cubic meters
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1 cm^3 = x m^3
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0.000 001
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1m^3 = x cm^3
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1 000 000
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Density
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density = mass/volume
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conversion factor
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a ratio derived from the equality between two different units that can be used to convert from one unit to the other
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dimensional analysis
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mathematical technique that allows you to use units to solve problems involving measurements quantity sought = quantity given x conversion factor
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1 ug = x g
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1 ug = 0.000 001 g
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1 Mm = x m
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1 Mm = 1 000 000
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3.5 mol = x umol
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3 500 000 umol
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a.10.5 g = _kg b. 1.57 km = _m c. 3.54 μg = _ g d. 3.5 mol = _μmol e. 1.2 L = _mL f. 358 cm3 = _m3 g. 548.6 mL = cm3
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0.0105 kg 1570 m 0.000 003 54 g 3,500,000 μmol 1200 mL 0.000 358 m3 548.6 cm3
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accuracy vs. precision
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accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured. precision refers to the closeness of a set of measurements of the same quantity made in the same way
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percentage error
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percentage error = |(experimental - accepted)| / accepted x 100 //compared quantitatively with correct or accepted value
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signficant figures
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sig figs in a measurement consists of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated
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zeros appearing between nonzero digits are
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significant
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zeros appearing in front of all nonzero digits are
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not significant
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zeros at the end of a number and to the right of a decimal point are
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significant
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zeros at the end of a number but to the left of a decimal point may or may not be ________. if a zero has not been measured or estimated but is just a placeholder, it is _______. a decimal point placed after zeros indicates that they are _______
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significant ; not significant ; significant
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Sig figs: 87 009 // 0.095 897 // 0.000 009 // 85.00 // 2000 // 2000.
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5 ; 5 ; 1; 4; 1; 4
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sig figs addition/subtracting
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when adding or subtracting decimals, the answer must have the same number of digits to the right of the decimal point as there are in the measurement having the fewest digits to the right of the decimal point.
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sig figs multiplication/division
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for multiplication or division, the answer can have no more significant digits than are in the measurement with the fewest number of significant figures
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conversion factors exact - no rounding. temperature?
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no significant figures for temperature
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scientific notation -> = ? <- = ?
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-> = 10^- <- = 10^+
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scientific notation
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have to have the same exponent factor
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TRUE/FALSE: in addition/subtraction, after you solve the question and after you put it in significant figures and scientific notation, do not put the answer in scientific notation BACK in significant figures.
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TRUE
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Multiplication
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M factors multiplied, exponents are added algebraically- when putting in scientific notation, significant digits twice.
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division
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m factors divided, exponents subtracted algebraically- significant figures, scientific notation, significant figures
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first 20 elements
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Hydrogen, Helium, Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine, Neon, Sodium, Magnesium, Aluminum, Silicon, Sulfur, Phosphorus, Chlorine, Argon, Potassium, Calcium
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ANALYZE, PLAN, COMPUTE, EVALUATE
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first step in solving a quantitative word problem is to read the problem carefully at least twice and to analyze the information in it. the second step is to develop a plan for solving the problem. the third step involves substituting the data and necessary conversion factors into the plan. Examine your answer to determine whether it's reasonable.
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directly proportional
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two quantities are directly proportional to each other if dividing one by the other gives a constant value
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inversely proportional
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two quantities are inversely proportional to each other if their product is constant
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determine the number of significant figures: 6.002, 0.0020, 10.0500, 7000, 7000.
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4; 2; 6; 1; 4
