Measurements All measurements include as many accurate numbers as possible and one estimated value. The numbers of accurate values a measurement has depends upon how the piece of equipment is graduated. Examples Examples

MASS MEASURES THE QUANTITY OF MATTER IN A SUBSTANCE BASIC UNIT- Kg kilogram INSTRUMENT - balance

WEIGHT Gravitational force between two bodies INSTRUMENT : scale BASIC UNIT: N newton

Volume/Capacity The amount of space occupied by something INSTRUMENT: Graduated cylinder UNIT: L Liters ( m 3 cubic meters) How many cm 3 in one m 3 ?

LENGTH Distance between two points INSTRUMENT: ruler UNITS: m meter

Temperature A measure of the average kinetic energy of a substance INSTRUMENT: thermometer UNITS: K kelvin (absolute scale) O C Celcius o F Fahrenheit Temperature and molecular motion Temperature scales

Celcius scale Devised by Anders Celcius in 1742 Based on the freezing point and boiling point of water. Diagram showing two fixed points:

Kelvin Scale Known as the absolute scale. Devised by William Kelvin A temperature scale on which the zero point would be absolute zero (theoretically the lowest possible temperature) and the size of the degree would be the same as celcius.

Note: a one degree change on the Kelvin scale is equal to a one degree change on the Celcius scale. Diagram:

K= C C = K - 273

PRECISION Precision refers to the degree of reproducibility of a measured quantity, that is, the closeness of agreement when the same quantity is measured several times

ACCURACY Accuracy : refers to how close a measured value is to the accepted or “real” value. High precision numbers are not always accurate. But it is more likely that measurements of high precision are more accurate.