Chemistry Ch 2 #1

Three Parts of Measurement

Three Parts of Measurement

unit (mass, length, volume, etc), magnitude (4.27 ft, 3 g), and uncertainty (4.5 or 4.6?)

Significant Figures

include all numbers in a measurement that are known for certain plus one that is uncertain

Multiplication and Division Rounding

The product or quotient should have the same number of significant figures as the number with the fewest significant figures in the original problem.

Addition and Subtraction Rounding

The answer should have the same number of decimal places as the least precise number (fewest number of decimal places) in the original problem

Science Rounding Rules

If the digit to be dropped is:

Greater than 5 →round one up

Less than 5 → do not change

Equal to 5 (remainder must be exactly five) → If previous digit is even, do not change it. If previous digit is odd, round it up to make it even

Accuracy

refers to the closeness of a measurement to a true or accepted value.

Precision

refers to the reproducibility of a series of measurements: how close they are to each other.

Observed Value

the value you obtain from doing an experiment; the experimental or measured value

True Value

the actual or theoretical value found in the literature as the accepted or standard value

% Error Formula

= observed value - true value x 100

true value

Absolute Error

Numerator of the % Error equation (OV - TV); may be positive or negative

meter (m)

SI unit for length

kilogram (k)

SI unit for mass

seconds (s)

SI Unit for time

Kelvin (K)

SI Unit for temperature

mole (mol)

SI Unit for amount of substance

ampere (A)

SI Unit for electric current

candela (cd)

SI Unit of luminous intensity

square meter (m²)

SI derived unit for area

cubic meter (m³)

SI derived unit for volume

meter per second (m/s)

SI derived unit for velocity

meter per second squared (m/s²)

SI derived unit for acceleration

gram per cubic centimeter (g/cm³)

SI derived unit for density

joule (J)

SI derived unit for energy

pascal (Pa)

SI derived unit for pressure