Units of Measurement

Scientific (Exponential) Notation Numbers associated with scientific measurements are often very large or very small. Scientific notation is a method for making very large or very small numbers more compact and easier to write. Scientific notation expresses a number as a product of a number between 1 and 10 and the appropriate power of 10.

The easiest way to determine the appropriate power of 10 is to start with the number being represented and count the number of places the decimal point must be moved to obtain a number between 1 and 10. For example, for the number we must move the decimal point seven places to the left to get 6.5 (a number between 1 and 10). Remember: When the decimal point is moved to the left, the exponent of 10 is positive.

We can represent numbers smaller than 1 by using the same convention, but in this case the power of 10 is negative. For example, for the number 0.000323 we must move the decimal point four places to the right to obtain a number between 1 and 10: This requires an exponent of -4, so 0.000323 = 3.23 x 10-4. Remember: when the decimal is moved to the right, the exponent of 10 is negative.

Measurements Quantitative information (qualitative data would be descriptions of your observations). Measurements represent quantities (something that has magnitude, size, or amount).

ampere candela kelvin mole meter kilogram second SI Measurement Scientists use the International System of Units (SI). This system was adopted in 1960 by the General Conference on Weights and Measures. ampere candela kelvin mole meter kilogram second

SI Base Units There are seven SI base units (meter, kilogram, second, kelvin, mole, ampere, candela). Most other SI units are derived from these. Prefixes are added to the names of the SI base units to represent quantities larger or smaller than the base units. (1000 m = 1 kilometer)

Mass is the measure of the quantity of matter (SI unit is the kilogram). Measured by using a balance. Weight is a measure of the gravitational pull on matter and is measured by using a spring scale. The SI unit for length is the meter.

Derived SI Units Combinations of SI base units form derived units. Derived units are produced by multiplying or dividing standard units. Volume is the amount of space occupied by an object. The SI unit for volume is m3 (1 mL = 1 cm3).