UNITS OF MEASUREMENT The metric system

WHAT ARE UNITS OF MEASUREMENT? Units describe what aspect of matter is being measured Qualitative: something that is described Using the senses Quantitative: something that is measured Examples: Unit of distance – mile Unit of volume – gallon Unit of time – hour Unit of weight - pound

SI UNITS OF MEASUREMENT SI – Standards International Set of units that are recognized by the scientific community In science (unlike math), you need a unit for EVERY NUMBER These are the units we will be using in this class – not English units

THE SI UNITS (THE METRIC SYSTEM) Metric system is a base 10 system To convert from one unit to another, you just move the decimal left or right These are the most commonly used in this class Distance – meter (m) Mass – gram (g) Volume – liter (L) Time – second (s) Temperature – degrees Celsius (°C) Energy – Joules (J)

METRIC PREFIXES Prefixes modify the base unit Gram, Liter, meter, etc. You can put a prefix in front of any base unit: kg is a kilogram: this means 1000 grams km is a kilometer: this means 1000 meters kL is a kiloliter: this means 1000 liters

MASS – A QUICK EXPLANATION Mass and weight are different Weight can change. It is not an absolute value Weight depends upon the force of gravity You weigh more on Earth than on the Moon Mass cannot change. It is an absolute value Mass depends on the amount of matter in a substance Mass does not change with gravity

FOR THE FOLLOWING EXAMPLES: Make sure that every table has at least 1 textbook If no one at the table has a text, come up and grab one per table. Open the book up to p. 23

METRIC CONVERSIONS – Copy for your notes Giga G 109 Mega M 106 Kilo k 103 Hecto h 102 Deka dK 101 Base unit 100 Deci d 10-1 Centi c 10-2 Milli m 10-3 Micro u 10-6 Nano n 10-9 Pico p 10-12

STEPS TO CONVERT : EXAMPLE: 100mm = _?_cm Find the meaning of all the prefixes in a conversion and look at the exponents 100mm = _____ cm m (milli) = 10-3 c (centi) = 10-2 Take the absolute difference in the exponents (-3) – (-2) = |-1| = 1

STEPS TO CONVERT This is the number of spaces you are going to be moving the decimal To figure out the direction, look at the units If you go from smaller unit to bigger, move the decimal to the left If you go from bigger unit to smaller, movver the decimal to the right

STEPS TO CONVERT In the example, we are going from mm to cm mm is smaller than cm, therefore we move the decimal to the left 100. mm  move decimal one space to the left 100mm = 10cm Important note: Always use the exponents, don’t just count the spaces.

PRACTICE Try the following 3 conversions IN YOUR NOTES: 1500 g = __?__ kg 63.3 hL = __?__ cL 122,000 nm = __?__ cm

ANSWERS 1.500 g 633,000 cL 0.122 mm