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Chapter 2 : Measurements and Calculations
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Gravity
Terms in this set (32)
Scientific method
is a logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypotheses, and formulating theories that are supported by data.
Observing
is the use of senses to obtain information, involves making measurement or collecting data.
Qualitative
descriptive, non-numerical information
the sky is blue
Quantitative
Numerical information
25.7 grams
System
is a specific portion of matter in a given region of space that has been selected for study during an experiment or observation.
Hypothesis
testable statement
"if-then"
Model
in science is more than a physical object; it is often an explanation of how phenomena occur and how data or events are related.
Theory
is a broad generalization that explains a body of facts or phenomena.
quantity
is something that has magnitude, size, or amount. Is not the same measurement.
SI Base Units
meter, kilogram, second, kelvin, mole, ampere, candela
SI Prefixes
tera 1x10^12
giga 1x10^9
mega 1x10^6
kilo 1000
hecto 100
deka 10
base 10^0
deci 0.1
centi 0.01
milli 0.001
micro 1x10^-6
nano 1x10^-9
pico 1x10^-12
femto 1x10^-15
atto 1x10^-18
WEIGHT
THE GRAVITATIONAL PULL ON MATTER
Derived units
Combinations or SI base units form
Derived SI Units
Area square meter
volume cubic meter
density kilograms per cubic meter
molar mass kilograms per mole
concentration moles per liter
molar volume cubic meters per mole
energy joule
Volume
is the amount of space occupied by an object
Liter
is equivalent to 1000 cm^3
Density
is the ratio of mass to volume, or mass divided by volume
intensive property
usually decreases w/ increasing temperature
D=M/V
V=M/D
M=VD
Conversion factor
is a ratio derived from the equality between two different units that can be used to convert from one unit to the other
Accuracy
refers to the closeness of the measurements to the correct or accepted value of the quantity measured
Precision
refers to the closeness of a set of measurements of the dame quantity made in the same way
Percent error
is calculated by subtracting the experimental value from the accepted value, dividing the differences by the accepted value, and then multiplying by 100.
Significant figures
in a measurement consist of all the digits known with certainty plus one final digit, which is somewhat uncertain or it is estimated.
Rules for Determining Sig Zeros
1. Zeros appearing between nonzero digits are significant
40.7 (3sigfigs) 87009(5sigfigs)
2. Zeros appearing in front of all nonzero digits are not sig.
0.095897(5sigfigs) 0.0009 (1sigfig)
3. Zeros at the end of a number and to the right of a decimal point are sig.
85.00 (4sigfigs) 9.000000000(10sigfigs)
4. Zeros at the end of a number but to the left of a decimal point may or may not be sig. If a zero has not been measured or estimated but is just a place holder, it is not sig. A decimal point placed after zeros are sig.
2000 (assume it has 1sigfig)
2000. (4sigfigs)
Rules for Rounding Numbers
5, not followed by a nonzero digit, and the preceding is even
then the last digit should stay the same
78. 65 mL --> 78. 6 mL
(because 6 is even)
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.
25.1+2.03=27.13
27.13 rounds to 27.1
FOR MULTIPLICATION AND DIVISION, THE ANSWER CAN HAVE NO MORE SIG FIGS THAN ARE IN THE MEASUREMENT WITH THE FEWEST SIG FIGS.
3.05/8.47=0.360094451
3 SIG FIGS, ROUNDS TO 0.306
Conversion factors ar exact, so the answer wouldn't be rounded.
4.608 m x 100cm/ m = 460. 8 cm
Scientific Notation
numbers are written in the form Mx10^n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number.
Left positive.
Right negative.
MOVING THE DECIMAL
4.2 x 10^4 = 42 x 10^3
MOVE DECIMAL TO RIGHT, DECREASE EXPONENT
LEFT TO INCREASE.
Directly proportional (/)
Two quantities are ____ to each other if dividing one by the other gives a constant value.
Mass and volume are directly proportional.
y/x=k
k is constant
y=kx
produce linear graphs
Inversely proportional (multiply)
Two quantities are inversely prop. to each other if their product is constant.
An example is the relationship between the speed of travel and time.
"y is proportional to 1 divided by x"
xy=k
produces a hyperbola
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