C hapter 1 S ection 3 M easurement

Scientific Notation Makes very large or very small numbers easier to work with (examples: 2,630,000,000,000,000,000 is much easier to read and do calculations when written as 2.63 x 10 18, and is easier to use when written as 5.9 x ) A way of expressing a number as a product of a number (between 1 and 10) and a power of 10 The exponent on the 10 tells you how many places the decimal has been moved

A positive power of 10 is a number larger than 1, so multiplying by a positive power of 10 must give a larger number Example: 3.46x 10 5 = ; which is the 3.46 with the decimal place moved 5 places to the right (to make it a big number). A negative power of 10 is a number smaller than one, so multiplying by a negative power of 10 must give a smaller number Example: 2.67 x = ; which is the 2.67 with the decimal place moved 6 places to the left (to make it a small number) In short : positive power of 10 = big number = move right negative power of 10 = small number = move left

positive power of 10 = big number = move right 10 3 = = 1000 negative power of 10 = small number = move left = 1/10 1/10 1/10 = 1/1000

SI Units of Measurement (Système International d’Unités) International System of Units A revised version of the metric system used by scientists The seven base units are metric units The derived are combinations of the base units Metric prefixes indicate what power of 10 something should be multiplied/divided by

QuantityUnitSymbol AreaSquare meterM2M2 VolumeCubic meterM3M3 DensityKilograms per cubic meterkg/m 3 PressurePascal (kg/ms 2 )Pa EnergyJoule (kgm 2 /s 2 )J FrequencyHertz (1/s)Hz Electric chargeCoulomb (as)C Derived Units

Limits of Measurement Precision is how exact a measurement is Significant Figures (digits) are all of the digits that are known in a measurement plus the last digit that is estimated The precision of a calculated answer is limited by the least precise measurement used in the calculation Example: You weigh a block of iron to be g, and measure the volume to be 3.3 cubic cm. You calculate the density as g / 3.3 cm 3 = g/cm 3. Your least precise measurement had only 2 significant figures, so your answer can have only 2 significant figures 7.8 g/cm 3

Accuracy Accuracy is the closeness of a measurement to the actual value of what is being measured.

Precise – repeatable and reliable; getting the same measurement each time Accurate – capable of providing a correct reading or measurement; getting the correct reading or measurement