Presentation on theme: "The SI System or How to Know “How Much?”. The Metric System Officially called the SI System Based on increments of 10 (one decimal place or zero) A good."— Presentation transcript:
The SI System or How to Know “How Much?”
The Metric System Officially called the SI System Based on increments of 10 (one decimal place or zero) A good measurement has a number and a unit Prefixes on the unit name tell you how many zeroes to put before or after a number Used in every country around the world except the USA and Báhrain The official measurement system of the USA since the late 1800s
Why you don’t already know the Metric System Your parents didn’t know it No incentive for companies to switch You are still being taught the Imperial System through everyday experiences - Recipes - Consumer goods There is a slow, steady inclusion process
Base Units Base units are defined by only one measurement
Length Distance from one point to another Meters (m) are the base units (a little longer than a yard) For smaller items, centimeters (about one knuckle), and millimeters (the thickness of a dime) are used
Mass Amount of substance (number of particles) in an object Gram (g) is the base unit It is too small for some common measurements (about 1 paper clip of matter) Usually use the kilogram (kg) for basis of comparisons A kilogram is a little more than 2 pounds
Time How long it takes for something to happen Also called “Time Elapsed” or “Elapsed Time” Seconds (s) are the base unit Can lead to large numbers (1hr = 3600s)
What would you use to measure the length of your arm? 1.Liters 2.Meters 3.Grams 4.Grams/Milliliter
What would you use to measure how much sugar is in one teaspoon? 1.Liters 2.Meters 3.Grams 4.Kilograms
What would you use to measure how much you weigh? 1.Liters 2.Meters 3.Grams 4.Kilograms
What would you use to measure the width of the room? 1.Liters 2.Meters 3.Grams 4.Grams/Milliliter
Derived Units of the SI System Derived units are defined by two or more measurements Volume Amount of space taken up by a substance Liters (L) are the base units (a little more than a quart) Liters are too large for some measurements, so milliliters (mL) are often used
What would you use to measure how much water is in a pool? 1.Liters 2.Meters 3.Grams 4.Grams/Milliliter
More Derived Units Density Amount of matter in an object divided by the space taken up by the object “How much stuff is in how much space” Usually expressed in grams per milliliter (g/mL) for smaller amounts Expressed in kilograms per liter (kg/L) for larger amounts THE NUMBER DOES NOT CHANGE
SI Prefixes Used to show a number of base units Think of them as coefficients (multipliers) Easy to convert by sliding the decimal
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
Testing your knowledge… Answer the five questions… Use the “Metric Ruler” to slide the decimal to get the desired units… Ready?
What is 25mm in m? 1.2.5m m m m
How many grams are 1.12kg? 1.112g g g g
How many Liters are 591mL? L L L L
What is 2.5cm in mm? 1.250mm 2..25mm 3.25mm mm
0.355L is how many mL? mL mL 3.355mL mL
Volume and Density in the SI System Why things float or sink, metrically
Metric Density and Water The SI system is better than the English/Imperial system at converting length measurements to volume measurements. The density of water is defined as 1g of water occupying 1cm 3 of water at 4 C. The density of water is 1 g/cm 3.
Density Formula Knowing the volume, mass, and/or density of a substance will allow you to infer as to the missing quantity. Density = massd = m volumev m = d vv = m d
Some Common Densities in g/cm 3 Air Titanium4.5 Wood – Cherry0.433Iron7.86 Gasoline0.721Steel8.03 Water – ICE0.897Brass8.553 Mineral Oil0.914Copper8.9 Paper0.929Silver10.5 Water - 4 C1.000Lead11.37 Glass2.6Uranium18.74 Aluminium2.643Gold19.32 Sapphire3.99Platinum21.3 Iridium, a rare metal found in asteroids, comets, and meteorites has the highest natural density at g/cm 3.
Will it float? When any two substances are mixed, the less dense substance will float on the more dense substance This causes rainbows on water and convection.
Significant Digits 1. Zeros appearing between nonzero digits are significant Zeros appearing in front of all nonzero digits are not significant Zeros at the end of a number & to the right of a decimal point are significant &
Significant Digits 4. Zeros at the end of a # but to the left of a decimal point may or may not be significant. 30 or 30.