Measurement

-is a quantity that has both a NUMBER AND A UNIT

measurement without units are meaningless

units typically used is science are those of the International system of units (SI)

SI Units (The international system of units)

• SI measurements-- SI units are defined in terms of standards of measurement

-the standards are objects or natural phenomena that are constant values, easy to preserve and reproduce, they are also practical in size.

-They are called SI units because of the French name the systeme international dunites

Metre

Symbol - m

Quantity - length

Kilogram

Symbol - kg

Quantity - mass

Second

Symbol - s

Quantity - time

Ampere

Symbol - A

Quantity - Electric Current

Kelvin

Symbol - K

Quantity - temperature

Candela

Symbol - cd

Quantity - luminous intensity

Mole

Symbol - mol

Quantity - amount of substance

Accuracy

-closeness of measurement to the correct or accepted value of the quantity measured

- to evaluate the accuracy of a measurement, the measure value must be compared to the accepted or correct value

Precision

- closeness of a set of measurements of the same quantity made in the same way

- to evaluate the precision of a measurement, you must compare the values to two or more repeated measurements

Accepted Value

- is the theoretical value, published or textbook value, or the calculated value

Experimental Value

is the value measured in the lab

- error is the difference between the experimental value and the accepted value

- error = experimental value - accepted value

- sources of error:

• instrurment malfunction
• Human mistake (carelessness or haste)

Scientific Notation

- we will use scientific notation when working with extremely large or small numbers

- numbers are written in the format: M*10^n M is a number greater than 1 but less than "n" is a whole number exponent

- a positive exponent indicates a BIG number

- a negative exponent indicates a small number

Determining Error

- percent error: describes the accuracy of an individual value or of an average experimental value when compared quantitively with the correct or accepted value

- percent error experimental - accepted *100

Accepted