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Chapter 3: Scientific Measurement
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Gravity
Terms in this set (62)
(3.1) measurement
a quantity that has both a number and unit
ie. 67 inches
(3.1) importance of measurement
-vital parts of experimental sciences ---> important to be able to make a measurement and make sure it is correct
(3.1) scientific notation
a given number is written as the product of two numbers: a coefficient and 10 raised to a power in order to simplify a tedious number
ie. ordinary notation: .0000052
scientific notation: 5.2 x 10^-6
(3.1) rules of significant figures
1. coefficient is always a number EQUAL or GREATER than 1 OR LESS than 10
2. All NON-ZERO digits are SIGNIFICANT
3. All ZERO digits are INSIGNIFICANT
4. ZEROS between NON-ZEROS are SIGNIFICANT
5. ZEROS before the first whole numbers are INSIGNIFICANT (to the left of the whole number) and act as "placeholders"
6. ZEROS after the first whole number are SIGNIFICANT
7. ZEROS at the END or to the right of a DECIMAL POINT are always SIGNIFICANT
8. ZEROS at the end or two the right of an "understood" decimal point are INSIGNIFICANT
9. COUNTING = INFINITE significant figures
10. DEFINED RELATIONSHIPS = INFINITE significant figures
(3.1) accuracy
a measurement of how CLOSE a measurement come to the ACTUAL or TRUE value of whatever is measured
(3.1) precision
a measure of how CLOSE a series of measurement are to ONE ANOTHER
(3.1) how to evaluate accuracy
the measured value is compared to the actual value
(3.1) how to evaluate precision
compare the values of two or more repeated measurements
(3.1) accepted value
correct value based on reliable references
(3.1) experimental value
the value measured in the lab
(3.1) error
the difference between the experimental value and the accepted value (can be positive or negative):
ERROR= experimental - accepted value
(3.1) percent error
the absolute value of the error divided by the accepted value, multiplied by 100% (always positive value):
PERCENT ERROR= ([error]/accepted value) x 100%
(3.1) significant figures
all of the digits that are known, plus the last digit that is estimated (because the last digit is ALWAYS uncertain)
(3.1) why is it so important to have the correct number of sigfigs?
because calculated answers depend on the number of sigfigs in the values used in the calculation
(3.1) when are sigfigs used?
sigfigs are always used in measurements because measurements are produced by instruments that NEVER has 100% certainty, so it's subject to ERROR
(3.1) sigfigs in calculations
in a calculated answer, the answer cannot be more precise than the lest precise measurement from which it was calculated
ie. 7.7 x 5.4 = 41.58 ---> 42 (2 sigfigs=least precise)
(3.1) how to round
1. decide how many sigfigs the answer should have
2. round to as many digits counting to the left (less than 5 --> round out, greater than 5 --> round up)
(3.1) addition and subtraction rounding
round to the same number of DECIMAL places as measurement with the LEAST number of decimal places
(3.1) multiplying and dividing rounding
round answer to the same number of SIGFIGS as the measurement with the LEAST number of sigfigs
(3.1) finite vs infinite sigfigs
FINITE: sigfigs in terms of MEASUREMENTS bc tools are subject to ERROR
INFINITE: an ACTUAL COUNT or an established RELATIONSHIP bc it is 100% accurate
(3.2) what do all measurements depend on?
the units of measurement that serve as reference standards
-easily convertible from one unit to another because they are all based by numbers of 10
(3.2) The International Systems of Units (SI)
revised version of the metric system that is standard internationally - some non-SI units are more common for convenience sake
(3.2) five SI base units
the meter (m) - length, the kilogram (kg) - mass, the kelvin (K) - temperature, the second (s) - time, and the mole (mol) - amount of substance
(3.2) units of length
all measurements of length can be expressed in "meters," sometimes expressed in its prefix form of the SI
(3.2) prefixes of units of length
a another name used to simplify a smaller or larger measurement -- sometimes used more commonly than the SI unit
ie. millimeter = 1/1000 of a meter
kilometer = 1000 meters
(3.2) COMMON metric units of length
the centimeter (100 cm = 1 m), the meter, and the kilometer
(3.2) volume
the pace occupied by any sample of matter which changes upon temperature
(3.2) how to find volume
L x W x H ---> volume is expressed in units of measurement
(3.2) liter
a non-SI, but more common unit of volume that measures 10 cm along each edge (1 L = 1 cubic decimeter- 10 cm)
(3.2) COMMON metric units of volume
the liter, milliliter, cubic centimeter, and microliter
(3.2) devices for measuring liquid volumes
cylinders, pipets, burets, volumetric flasks, and syringes
(3.2) what is mass measured in comparison to?
the standard of mass; the kilogram
(3.2) kilogram
the mass of 1 L of liquid water at 4 degrees C
(1 kg = 1000 grams)
(3.2) gram
1/1000 of a kilogram
(3.2) COMMON metric units of mass
the kilogram, gram, milligram, and microgram
(3.2) what can be used to measure the mass of an object
a platform balance
(3.2) weight
a force that measures the pull on a given mass by gravity
(3.2) weight vs mass
WEIGHT: relies on gravity, changes based on gravity
MASS: stays unchanged regardless of gravity
----> objects can be weightless but not massless
(3.2) temperature
the measure of how hot or cold an object is based on the absence or presence of heat
(3.2) what determines temperature?
heat transfer (always moves from high to low temperatures):
-absence = cold
-presence = hot
(3.2) what tool do you use to measure temperature?
thermometer
(3.2) how do thermometers work?
because all substances expand and contract with an increase in temperature, the liquid in a thermometer expands and contracts more than the volume of the glass
(3.2) what are the 2 most common, equivalent units of temperature?
Kelvin and Celsius
(3.2) similarities and differences of K and C
Similarities: both based on the freezing and boiling point of water
difference of freezing and boiling points are intervals of 100
change in 1 degree C = to change in 1 K
Differences: the value of the freezing and boiling point of water
the degree sign is NOT used in K
(3.2) Celsius Scale
measurement of temperature that sets the freezing point at 0 degrees C and the boilingpoint at 100 degrees C
(3.2) Kelvin Scale
measurement of temperature that sets the freezing point at 273.15 K and the boiling point at 373.15 K
(3.2) Absolute Zero
the zero point on the Kelvin scale (-273.15 K)
(3.2) conversions of temperature
K = degrees C + 273
degrees C = K - 273
(3.2) Energy
the capacity to do work or produce heat
(3.2) COMMON units of energy
the joule and the calorie
(3.2) the Joule
the SI unit of energy
(3.2) the calorie
the quantity of heat that raises the temperature of 1 g of pure water by 1 degree C
(3.2) conversions of energy
1 J = 0.2390 cal
1 cal = 4.184 J
(3.4) density
the ratio between mass of an object to its volume
D = M (g) / V (cm^3)
(3.4) why do some volumes vary?
because they have different densities although they may have the same mass
(3.4) what can density determine?
each substance has a unique density, so density can determine a substance
(3.4) is density intensive or extensive?
intensive
(3.4) what does density depend on
the composition of a substance, not on the size of the sample
(3.4) how can you determine if something will float or sink?
the ratio of the mass of an object to its volume
(3.4) what happens to volume as temperature rises?
the volume rises too
(3.4) what happens to mass as the temperature rises?
the mass remains the same
(3.4) what happens to density as the temperature rises?
the density will change because of the change in volume -- the density of a substance generally decreases as the temperature increases
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