Chapter 1 Science Skills

1.3 Measurement

SI Units When you measure things, what units do you typically use? Feet, inches, miles, pounds, gallons.. This is referred to as the “English System.” In science, the metric system is used because it is a universal language that anyone can understand regardless of what country they are in. The units in the metric system are known as SI units (International System of Units). Sometimes there are variables that are larger or smaller than the base unit, so we use metric prefixes to make measurements more convenient. Examples of Base units… meter, liter, gram, Pascal,…

The Fundamental SI Units (Le Système International, SI)

Prefix Symbol Meaning Mega M Kilo K Hecta H Deca D Base Unit 1 deci d 106 Kilo K 103 Hecta H 102 Deca D 101 Base Unit 1 deci d 10-1 centi c 10-2 milli m 10-3 micro  10-6 nano n 10-9 pico p 10-12

Conversions To make a measurement, it takes more of a small unit or less of a large unit. A person’s height could be 1.85 m, a fairly small number; or it could be 185 cm, a fairly large number. So, if you are converting into a smaller unit, multiply the measurement to get a big number. If you are converting into a larger unit, divide the measurement to get a smaller number.

1 Kilometer equals how many meters? 1000 meters because the Kilometer prefix represents a thousand. So since there is 1 Kilometer, one times 1000 is 1000 meters.

How many meters in 1000 centimeters? 10 meters because the centi prefix represents one hundreth of a meter. We have to divide 1000 centimeters by 100 to get our answer. Easy trick to remember…up the chart you divide or down the chart you multiply the number of steps you move.

Try These Write 550 millimeters as meters. Write 3.5 seconds as milliseconds Write 1.6 Kilograms to grams Write 2500 milligrams to Kilograms Write 4.00 centimeters to micrometers Write 2800 decimoles to moles Write 6.1 amperes to milliamperes Write 3 Kilograms to milligrams .550m 3500ms 1600g .0025 kg 40,000 um 280 mol 6100 ma 3,000,000mg