Metric System Scientific Measurements

Metric System Developed by the French in the late 1700’s. Developed by the French in the late 1700’s. Based on powers of ten, so it is very easy to use. Based on powers of ten, so it is very easy to use. Used by almost every country in the world, with the notable exception of the USA. Used by almost every country in the world, with the notable exception of the USA. Especially used by scientists. Especially used by scientists. Abbreviated SI, which is French for Systeme International. Abbreviated SI, which is French for Systeme International.

Metric Prefixes Regardless of the unit, the entire metric system uses the same prefixes. Regardless of the unit, the entire metric system uses the same prefixes. Common prefixes are: Common prefixes are: kilo = 1000 centi = 1/100 th milli = 1/1000 th 1 meter = 100 centimeters= 1000 millimeters

Length Length is the distance between two points. Length is the distance between two points. The SI base unit for length is the meter. The SI base unit for length is the meter. We use rulers or meter sticks to find the length of objects. We use rulers or meter sticks to find the length of objects.

Mass Mass is the amount of matter that makes up an object. Mass is the amount of matter that makes up an object. A golf ball and a ping pong ball are the same size, but the golf ball has a lot more matter in it. So the golf ball will have more mass. A golf ball and a ping pong ball are the same size, but the golf ball has a lot more matter in it. So the golf ball will have more mass. The SI unit for mass is the gram. The SI unit for mass is the gram. A paper clip has a mass of about one gram. A paper clip has a mass of about one gram. The mass of an object will not change unless we add or subtract matter from it. The mass of an object will not change unless we add or subtract matter from it.

Measuring Mass We will use a triple beam balance scale to measure mass. We will use a triple beam balance scale to measure mass. Gravity pulls equally on both sides of a balance scale, so you will get the same mass no matter what planet you are on. Gravity pulls equally on both sides of a balance scale, so you will get the same mass no matter what planet you are on.

Weight Weight is a measure of the force of gravity on an object. Weight is a measure of the force of gravity on an object. Your weight can change depending on the force of gravity. The gravity will change depending on the planet you are on. Your weight can change depending on the force of gravity. The gravity will change depending on the planet you are on. The SI unit for weight is the Newton (N). The SI unit for weight is the Newton (N). The English unit for weight is the pound. The English unit for weight is the pound.

Gravity Gravity is the force of attraction between any two objects with mass. Gravity is the force of attraction between any two objects with mass. The force depends on two things: The force depends on two things: more distance = less gravity = less weight more distance = less gravity = less weight less distance = more gravity = more weight less distance = more gravity = more weight more mass = more gravity = more weight more mass = more gravity = more weight less mass = less gravity = less weight less mass = less gravity = less weight

Weight and Mass JillEarth 1 gravity Moon 1/6 th gravity Jupiter 2.5 gravities On orbit 0 gravity mass30kg30kg30kg30kg weight300N50N750N 0 Newtons Notice that Jill’s mass never changes. Her mother will not allow us to take parts off her, or add parts to her, so her mass stays the same. Jill is 30kg of little girl no matter where she goes!

Volume Volume is the amount of space contained in an object. Volume is the amount of space contained in an object. We can find the volume of box shapes by the formula Volume = length x width x height We can find the volume of box shapes by the formula Volume = length x width x height In this case the units would be cubic centimeters (cm 3 ). In this case the units would be cubic centimeters (cm 3 ). So a box 2 cm x 3 cm x 5cm would have a volume of 30 cm 3 So a box 2 cm x 3 cm x 5cm would have a volume of 30 cm 3 V = L x W x H

Base Units The base unit for volume is the Liter. The base unit for volume is the Liter. We measure volume with a graduated cylinder. We measure volume with a graduated cylinder.

Graduated Cylinders Liquids form curved, upper surfaces when poured into graduated cylinders Liquids form curved, upper surfaces when poured into graduated cylinders To correctly read the volume, read the bottom of the curve called the meniscus To correctly read the volume, read the bottom of the curve called the meniscus

Liquid Volume When the metric system was created, they decided that 1 cm 3 of water would equal 1 milliliter of water and the 1 mL of water will have a mass of one gram. When the metric system was created, they decided that 1 cm 3 of water would equal 1 milliliter of water and the 1 mL of water will have a mass of one gram. 1cm 3 water =1 ml of water = 1 gram 1cm 3 water =1 ml of water = 1 gram

Water Displacement We can use water displacement to find the volume of objects that are not boxed shaped. We can use water displacement to find the volume of objects that are not boxed shaped. We can put water in a graduated cylinder. If a rock causes the level to rise from 7 to 9 ml, the the rock must have a volume of 2-mL. We can put water in a graduated cylinder. If a rock causes the level to rise from 7 to 9 ml, the the rock must have a volume of 2-mL.

Water Mass and Volume 1 cm 3 water = 1 mL of water = 1 gram 1 cm 3 water = 1 mL of water = 1 gram So what would be the mass of 50 mL of water be? So what would be the mass of 50 mL of water be? 50 grams 50 grams So what would be the mass of 1 liter of water be? So what would be the mass of 1 liter of water be? 1 L = 1000 mL so its mass would be 1000 grams or a kilogram. 1 L = 1000 mL so its mass would be 1000 grams or a kilogram.

Density Density is the amount of matter (mass) compared to the amount of space (volume) the object occupies. Density is the amount of matter (mass) compared to the amount of space (volume) the object occupies. We will measure mass in grams and We will measure mass in grams and volume in ml or cm 3 volume in ml or cm 3

Density Formula Density is mass divided by volume. Density is mass divided by volume. Density = mass/volume Density = mass/volume Remember, all fractions are division problems. Remember, all fractions are division problems. Since the unit for mass is grams, and the unit for volume is ml or cm 3, then the unit for density is g/ml, or g/ cm 3 Since the unit for mass is grams, and the unit for volume is ml or cm 3, then the unit for density is g/ml, or g/ cm 3

Understanding Density In the following illustrations, each will represent 1 cm 3. In the following illustrations, each will represent 1 cm 3. Each g will represent 1 gram. Each g will represent 1 gram. Mass = 24g Mass = 24g Volume = 8 cm 3 Volume = 8 cm 3 Density = 3g/cm 3 Density = 3g/cm 3 g g g g g g g g g g

g g g g g g g g cm 3.In other words, there are 3 grams in every cm 3.

Density Problem 2 g g Mass = 12 grams cm 3Volume = 6 cm 3 Density = 2 g/cm 3 In English we say the density of the object is 2 grams in every cubic centimeter.

Density Problem 3 g g g g g g g g g g g g g g g g g g Our previous problems were materials of uniform density. They were the same stuff throughout. But many materials are not. Gravel is a great example. Mass = 16 grams Volume = 8 mL Density = 2 g/mL

Water and Density Since 1-gram of water has a volume of 1-mL, then the density of water will always be 1 gram/ml. Since 1-gram of water has a volume of 1-mL, then the density of water will always be 1 gram/ml. 5o-mL of water will have a mass of 50 grams, so again the density of pure water will be 1 g/ml. 5o-mL of water will have a mass of 50 grams, so again the density of pure water will be 1 g/ml. A kg of water will have a volume of 1000-mL, so it’s density will be 1 gram/ml. A kg of water will have a volume of 1000-mL, so it’s density will be 1 gram/ml.

Floating and Sinking Less dense materials will float on top of more dense materials. Less dense materials will float on top of more dense materials. Objects with a density of less than 1-g/mL will float on top of water. Objects with a density of less than 1-g/mL will float on top of water. Objects with a density greater than 1 g/mL will sink in water. Objects with a density greater than 1 g/mL will sink in water.

Neutral Buoyancy Objects with a density equal to the density of water will float in mid water, at what ever level you place the object. Objects with a density equal to the density of water will float in mid water, at what ever level you place the object. Fish and submarines control their depth by changing their density. Fish and submarines control their depth by changing their density.

Objects that Sink! Objects with a density greater than 1 g/mL will sink in water. Objects with a density greater than 1 g/mL will sink in water.

Titanic Sails the Ocean Blue The Titanic is sailing on its maiden voyage. The Titanic is sailing on its maiden voyage. What is the density of this enormous, steel hulled ship, full of machinery, coal, people, and all sorts of heavy things? What is the density of this enormous, steel hulled ship, full of machinery, coal, people, and all sorts of heavy things? It’s floating, so it’s density must be less than 1 g/mL. It’s floating, so it’s density must be less than 1 g/mL. How can this be? How can this be? The Titanic is a hollow vessel full of air! The Titanic is a hollow vessel full of air!

Titanic verses Iceberg After HMS Titanic struck the iceberg, she started to fill with water. After HMS Titanic struck the iceberg, she started to fill with water. What happened to her density? What happened to her density? As she took on more and more water, her density got closer and closer to 1 g/mL. As she took on more and more water, her density got closer and closer to 1 g/mL. The denser the ship became, the lower she settled into the water. The denser the ship became, the lower she settled into the water.

Wreck of the Titanic What is the density of the Titanic resting on the ocean floor? What is the density of the Titanic resting on the ocean floor? Must be greater than 1 g/mL, as her steel hull is full of water instead of air. Must be greater than 1 g/mL, as her steel hull is full of water instead of air.

Comparing Densities Where is the most dense object?Where is the most dense object? Where is the least dense object?Where is the least dense object?

Density Review We don’t actually count g’s to find the mass of objects. How would you find the mass of a rock? We don’t actually count g’s to find the mass of objects. How would you find the mass of a rock? Use a balance scale. Use a balance scale. In real life, how would you find the volume of a rock? In real life, how would you find the volume of a rock? Use a graduated cylinder and see how much water the rock displaces. Use a graduated cylinder and see how much water the rock displaces.