The Metric System The “Language” of Science

Why Use the Metric System? All scientific measurements are made using the Metric System All scientific measurements are made using the Metric System Called the “SI System,” or - - Called the “SI System,” or - - “La Systeme International d’Unites” “La Systeme International d’Unites” It’s the simplest and easiest measuring system ever thought up! It’s the simplest and easiest measuring system ever thought up!

What makes it so easy? Based on 10 Based on 10 Multiply or divide by 10 when changing units Multiply or divide by 10 when changing units It’s a decimal system It’s a decimal system Can you think of a system we use every day that is a decimal system? Can you think of a system we use every day that is a decimal system?

Metric Units Length (how long) meter Volume (how much space is inside) liter Force (push or pull) Newton Mass (how much matter) gram Temp. (amount of heat) ° Celsius Time (how long it takes) second

Metric “Prefixes” kilo hecto Deka deci centi milli /10 (0.1) 1/100 (0.01) 1/1000 (0.001) GreekprefixesLatinprefixes Can you think of other words that use these prefixes? decade, cent, centipede, century, millipede

Converting or “Switching” Units For example: For example: 1000 m = 1 km 1000 m = 1 kmor 1 km = 1000 m 1 km = 1000 m How do we convert or switch units? How do we convert or switch units? If you’re converting to a smaller unit: If you’re converting to a smaller unit: multiply by 10, 100, or 1000 If you’re converting to a larger unit: If you’re converting to a larger unit: divide by 10, 100, or 1000 It takes practice! Here’s a shortcut rule: It takes practice! Here’s a shortcut rule: move the decimal point right or left! or, add or subtract a zero

Becoming Familiar with Metric One reason people find the metric system hard is because the units are unfamiliar to them One reason people find the metric system hard is because the units are unfamiliar to them Let’s make it easier: Let’s make it easier: What’s a millimeter? What’s a centimeter? What’s a meter? About the thickness of a paper clip or a coin About the width of your little finger About 3 feet, or one long step

Volume and Capacity Volume = the amount of space inside something Capacity = the amount of liquid a container can hold (based on its volume) Imagine a cube with sides of 1 dm x 1 dm x 1 dm: What’s it’s volume?multiply L x W x H Volume = 1 dm 3 or 1 cubic decimeter What’s it’s capacity? 1 dm 3 holds 1 liter of liquid (1 dm 3 is 1 liter!)

Volume and Capacity Here’s what we mean: Here’s what we mean: 1 dm 3 (or 1000 cm 3 ) holds 1 liter 1 dm 3 (or 1000 cm 3 ) holds 1 liter 1 cm 3 1 cm 3 holds 1 milliliter 1 dm or 10 cm 1 cm 1 liter 1 ml

Mass and Weight Mass = the amount of matter in an object Mass = the amount of matter in an object (measured in grams or kilograms) (measured in grams or kilograms) Weight = the force of gravity on mass Weight = the force of gravity on mass (measured in Newtons) (measured in Newtons) Your mass can’t change, but your weight depends on gravity: Your mass can’t change, but your weight depends on gravity: On the moon (only 1/6 Earth’s gravity),On the moon (only 1/6 Earth’s gravity), a 180-pound astronaut only weighs about 30 pounds. But, his mass is exactly the same as on Earth! (he’s made of the same amount of matter no matter where he is)But, his mass is exactly the same as on Earth! (he’s made of the same amount of matter no matter where he is)

What is Density? Objects with the same volume can have different masses. Objects with the same volume can have different masses. If more and more mass is crammed into the same space, an object is denser. If more and more mass is crammed into the same space, an object is denser. So what is density? How do we figure it out? So what is density? How do we figure it out? Density = mass ÷ volume If we know both the mass and the volume of an object, we can divide mass by volume to get the density. If we know both the mass and the volume of an object, we can divide mass by volume to get the density. Density is described using a combination of units: Density is described using a combination of units: grams per cubic centimeteror (g/cm 3 )

Measuring Density 1)First, use a triple beam balance to find the mass in grams. Calibrate!! 2)Next, use a graduated cylinder filled with water to measure the volume in cm3: An object placed in the container will displace, or push up the water. If the water is pushed up by 10 ml, what is the object’s volume? 10 ml = 10 cm3 !! Discovered by Archimedes (Eureka!!!) 3)Last, divide mass by volume to get the density in g/cm3.

Review Questions Answer the following questions to check your understanding. 1. What makes the metric system so simple and easy to use, even if we are not familiar with it? 2. Why is the metric system known as a decimal system? 3. What is the basic metric unit for length? mass? volume? etc. 4. Do you know each of the metric prefixes and what number or fraction they represent? 5. What are some familiar comparisons which help us to get a feel for a millimeter? A centimeter? A meter? etc. 6. What is the shortcut rule for multiplying or dividing by 10? 7. What is the difference between volume and capacity? 8. What is the difference between mass and weight? 9. What is density? How are mass and volume related to density? 10. How does Archimedes’ work give us a method for determining the density of any object?