SI Units • Système International d’Unités • Uses a different base unit for each quantity
Metric System Prefixes convert the base units into units that are appropriate for the item being measured.
WHY DO WE USE THE METRIC SYSTEM? • Almost all other countries are using the metric system • Other countries’ companies are refusing to buy products from the U.S. if not labeled in metric units • Scientists need a universal way to communicate data (SI Units)
APPROXIMATE CONVERSIONS BETWEEN METRIC & US LENGTH UNITS • A meter is about the same length as a yard • A meter is about three feet long • A decimeter is about four inches long • An inch is about 25 millimeters • A foot contains about 30 centimeters • A foot contains about 3 decimeters
WHAT DOES THE METRIC SYSTEM MEASURE? • The gram measures mass or how much something weighs • The liter measures volume which is used when measuring liquids • The meter measures the length of an object or the distance from place to place
THE METRIC CONVERSION CHART (STAIRCASE METHOD) To convert to a smaller unit, move decimal point to the right or multiply. Kilo 1000 units Hecto 100 units Deka 10 units Basic Unit Deci 0.1 units Centi 0.01 units Milli 0.001 units To convert to a larger unit, move decimal point to the left or divide
TRY THIS USING THE STAIRCASE METHOD 1000 mg = ______ g Step 1: Determine if you are going to go up or down the ladder. Step 2: Determine how many steps there are from milligrams to grams. Step 3: Move the decimal point the amount of places that was determined in steps 1 & 2.
TRY THIS USING THE STAIRCASE METHOD 1000 mg = ______ g 1 Step 1: Determine if you are going to go up or down the ladder. Step 2: Determine how many steps there are from milligrams to grams. Step 3: Move the decimal point the amount of places that was determined in steps 1 & 2.
TRY THIS USING THE STAIRCASE METHOD .15 L = __________ ml
TRY THIS USING THE STAIRCASE METHOD .15 L = __________ ml 150
Volume • The most commonly used metric units for volume are the liter (L) and the milliliter (mL). • A liter is a cube 1 dm long on each side. • A milliliter is a cube 1 cm long on each side.
Uncertainty in Measurements Different measuring devices have different uses and different degrees of accuracy.
Temperature: A measure of the average kinetic energy of the particles in a sample.
Temperature • In scientific measurements, the Celsius and Kelvin scales are most often used. • The Celsius scale is based on the properties of water. • 0C is the freezing point of water. • 100C is the boiling point of water.
Temperature • The Kelvin is the SI unit of temperature. • It is based on the properties of gases. • There are no negative Kelvin temperatures. • K = C + 273.15
Temperature • The Fahrenheit scale is not used in scientific measurements. • F = 9/5(C) + 32 • C = 5/9(F − 32)
A Standard Measurement System The Metric System
When and why was the metric system invented? • The metric system was invented in 1790 • The metric system was invented because countries were using many different systems of measurement causing confusion and lack of consistency
Who invented the metric system? • The metric system was invented by a group of French scientists
Metric System • A system of measurement used by the majority of countries on Earth based on the number 10
A Standard Measurement System The International System of Units (SI)
Scientists all over the world use the International System of Units to measure: • Length • Volume • Mass • Density • Temperature • Time
Figure 1: Calculating - How much larger is a kilo- than a deka-? • 100 times
Reading Checkpoint (page 45): SI units are based on multiples of what number? • SI units are based on multiples of 10 • Add a zero • Subtract a zero
Key Concept: Why do scientists use a standard measurement system? • Using SI as the standard system of measurement allows scientists to compare data and communicate with each other about their results • Using SI measurement also allows experiments to be repeated and most importantly achieve a desired result
What is length? • Length is the distance from one point to another
Length Units of Length
The basic unit of length in the SI system is the … • The basic unit of length in the SI system is the meter
The two units that measure the length of smaller objects are, … • millimeter • centimeter
Length Measuring Length
The longer lines on the metric ruler are called… • centimeters
The shorter lines on the metric ruler are called… • millimeters
Checkpoint One centimeter is divided into how many millimeters? • 10 millimeters (mm)
Figure 2: Calculating: Measure the turtle in figure 2 from the rear of its shell to the tip of its nose. Record its length in both centimeters and millimeters. • 10.5 cm • 105 mm
Density • The measure of how much mass is contained in a given volume
The formula of density is: Density = Mass / Volume