Unit 1 – Lecture 3

The Metric System aka: the SI, or International System of Units from the French, “Système international d'unités” a “base 10” [increments of 10] system one decimal place or zero Used everywhere around the world EXCEPT the USA Báhrain [small island off of Saudi Arabia] The official measurement system of the USA since the late 1800s

Why You Don’t Use It Yet Your parents didn’t know it No incentive for companies to switch You are still being taught the Imperial System through everyday experiences imperial system = foot, yard, gallon, etc. recipes consumer goods There is a slow, steady inclusion process 2 liters of soda

SI Prefixes Used to show a number of base units Think of them as coefficients (multipliers) Easy to convert by sliding the decimal

The Metric System – cont’d How many zeros? check the prefix K – kilo? H – hecto? Da – deca? b – [basic]? d – deci? c – centi? m – milli? good measure- ments have a number and a unit

SI Prefixes From the largest to the smallest kilo- hecto- deka- BASE deci- centi- milli /10 1/100 1/1000 “King Henry died by drinking chocolate milk.” Put your finger on the unit you have, move it to the unit you want Move your decimal the same number of places in the same direction that your finger moved

Practice Problems What is 25mm in m? m m m m

Practice Problems – cont’d How many grams are 1.12kg? g g g g

Practice Problems – cont’d How many Liters are 591 mL? L L L L

Practice Problems – cont’d What is 2.5cm in mm? mm 2..25mm 3. 25mm mm

Practice Problems – cont’d 0.355L is how many mL? mL mL mL mL

Base Units Base units use only one measurement type. KHD b dcm

Base Units – Length Length – the distance from one point to another base unit = meter [m] meter = a little longer than a yard [which is 3ft] For smaller items, centimeters [about one knuckle], and millimeters [the thickness of a dime] are used

Base Units – Mass Mass – the amount of matter in an object base unit = gram [g] about the mass of one paperclip…much too small for many measurements typically use kilogram [kg] for comparisons 1kg = ~2.2 lbs

Base Unit – Time Time = how long it takes for something to happen aka “Time Elapsed” or “Elapsed Time” base unit = seconds [s] can lead to large numbers (1hr = 3600s) often will convert seconds to a larger unit of hours

What would you use to measure… liters, meters, grams, grams/milliliter, kilograms …the length of your arm? …the width of the room? …how much sugar is in one teaspoon? …how much you weigh? …how much water is in a pool?

Derived Units in the SI System Derived Units = units that involve two or more measurements

Derived Units – Volume Volume - the amount of space taken up by a substance base unit for… liquids = liter [L] (a little more than a quart) solids = meter [m] liters can be too large for some measurements, so we often use milliliters (mL) one mL = one cc [cubic cm; cm 3 ]

Derived Units – Density Density = the amount of matter in an object divided by the space taken up by the object “How much stuff is in how much space.” grams per milliliter [g/mL] used for smaller amounts kilograms per liter [kg/L] for larger amounts

Derived Units – Density cont’d Density = mass / volume Mass = density x volume Volume = mass / density M D V