TOPIC: MEASUREMENT-A COMMON LANGUAGE

WHAT UNITS OF MEASURE DO YOU USE IN EVERYDAY LIFE?

THE METRIC SYSTEM & SI SYSTEM More than 200 years ago, most countries used their own measurement systems. In the 1790s, scientists in France developed a universal system of measurement known as the metric system. The metric system is a system of measurement based on the number 10. Modern scientists use a version of the metric system called the International System of Units, abbreviated as SI.

THE SI SYSTEM IS BASED ON THE NUMBER 10

WHY DO SCIENTISTS USE SI UNITS TO MEASURE?  Scientists all over the world use SI units to measure :  Length  Volume  Mass  Density  Temperature  Time  Using SI as the standard system of measurement allows scientists to compare data and communicate with each other about their results.

LENGTH  What is length?  Length is the distance from one point to another.  What is the basic unit of length?  The basic unit of length in the SI system is the meter (m).  Examples:  the distance from the floor to a doorknob  a softball throw  your height

MEASURING LENGTH  To measure objects smaller than a meter, scientists use units called the centimeter (hundredth) (cm) or the millimeter (thousandth) (mm).  Examples:  1 sheet of loose-leaf paper is equal to: 28 cm, 280 mm. What unit would you use to measure a long distance, such as a distance between two cities?  kilometer (km) The prefix –kilo means one thousand There are 1,000 meters in a kilometer. Example: If you were to draw a straight line between San Francisco and Boston, the line would measure about 4,300 kilometers. A millimeter is about the thickness of a plastic id card (or credit card). A fingernail is about one centimeter wide.

MEASURING LENGTH  A very common tool used to measure length is the metric ruler.  A metric ruler is divided into centimeters.  The centimeter markings are the longer lines numbered 1, 2, 3, and so on.  Each centimeter is then divided into 10 millimeters, which are marked by the shorter lines.