Measurement:
a that has both a number and a unit
Scientific Notation:
a given number is written as the product of two numbers: a coefficient and 10 raised to a power
Accuracy:
a measure of how close a measurement comes to the actual or true value of whatever is measured
Precision:
a measure of how close a series of measurements are to one another
Accepted Value:
the correct value based on reliable references
Experimental Value:
the value measured in the lab
Error:
the difference between the experimental value and the accepted value
Percent Error:
the absolute value of the error divided by the accepted value, multiplied by 100%
Significant Figures:
in a measurement include all of the digits that are known, plus a last digit that is estimated
How do measurements relate to experimental science?
Measurements are fundamental to the experimental sciences. For that reason, it is important to be able to make measurements and to decide whether a measurement is correct.
How are accuracy and precision evaluated?
To evaluate the accuracy of a measurement, the measured value must be compared to the correct value. To evaluate the precision of a measurement, you must compare the values of two or more repeated measurements.
Why must a given measurement always be reported to the correct number of significant figures?
Measurements must always be reported to the correct number of significant figures because calculated answers often depend on the number of significant figures in the values used in the calculation.
How does the precision of a calculated answer compare to the precision of the measurements used to obtain it?
In general, a calculated answer cannot be more precise than the least precise measurement from which it was calculated
International System of Units:
(SI) a revised version of the metric system
Meter:
(m) the basic unit of length or linear measure
Liter:
(L) a non-SI unit, a more convenient unit of volume
Kilogram:
(kg) the mass of an object is measured in comparison to a standard mass
Weight:
a force that measures the pull on a given mass by gravity
Temperature:
a measure of how hot or cold an object is
Celsius Scale:
sets the freezing point of water at 0 C and the boiling point of water at 100 C
Kelvin Scale:
the freezing point of water is 273.15 kelvins (K) and the boiling point is 373.15 (K)
Absolute Zero:
is equal to -273.15 C
Energy:
the capacity to do work or to produce heat
Joule:
(J) the SI unit of energy
Calorie:
(cal) the quantity of heat that raises the temperature of 1 g of pure water by 1 C
Which five SI base units are commonly used in chemistry?
The five SI base units commonly used by chemists are the meter, the kilogram, the kelvin, the second, and the mole.
Which metric units are commonly used to measure length, volume, mass, temperature, and energy?
Common metric units of length include the centimeter, meter, and kilometer.
Common metric units of volume include the liter, milliliter, cubic centimeter, and microliter.
Common metric units of mass include the kilogram, gram, milligram, and microgram.
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Conversion Factor:
a ratio of equivalent measurements
Dimensional Analysis:
a way to analyze and solve problems using the units, or dimensions, of the measurements
What happens to the numerical value of a measurement that is multiplied by a conversion factor? What happens to the actual size of quantity?
When a measurement is multiplied by a conversion factor, the numerical value is generally changed, but the actual size of the quantity measured remains the same.
Why is dimensional analysis useful?
Dimensional analysis provides you with an alternative approach to problem solving.
What types of problems can be solved using dimensional analysis?
Problems in which a measurement with one unit is converted to an equivalent measurement with another unit are easily solved using dimensional analysis.
Density:
the ratio of the mass of an object to its volume
What determines the density of an object?
Density is an intensive property that depends only on the composition of a substance, not on the size of the sample.
How does the density vary with temperature?
The density of a substance generally decreases as its temperature increases.