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SI (Système International d’unités) Metric System

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Introduction The thermometer says 39°C. – Do you need a warm jacket or your shorts Your school is 2 km away. – Do you need a ride or can you walk? A box has a mass of 500 grams. – Can you lift this by yourself or do you need help? Milk comes in a 2 liter container. – Can you share with your friends, or do you only have enough for yourself?

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Measurement History Since the beginning of time people have been measuring – Earliest recorded measurements involved length Egypt, 3000 BC – Cubit – Palm – Digit

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Length History Length units based on human body – Hand = width of human hand – Span = tip of pinky to tip of thumb – Foot = human foot – Cubit = tip of middle finger to elbow – Yard = tip of nose to thumb – Fathom = finger tip – finger tip of outstretched arms – Mile = “mille passe” = 1000 double paces

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Volume History Volume originally measured by heaps or handfuls – Gallon = container that held 10 pounds of water – Quarts = ¼ of gallon

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Mass History Mass originally measured by stones or seeds – Grain = based on number of seeds – Carat = based on “carob” seed – Stones = based on stones – Pound = money value once based on weight English still use “pound” for currency – Ounce = romans divided pound into 12 units “unciae” Later divided into 16 parts

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So What’s the Problem? Problems arose with accuracy, consistency, fairness – All feet, hands, paces aren’t the same – All handfuls and heaps aren’t the same – Different countries had different measurements Greeks divided their foot into 16 units Romans divided their foot into 12 units – Inch = Width of thumb – English used 3 barleycorns (seeds) to measure inch

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So What’s the Answer? Problems arose with accuracy, consistency, fairness – Standards were established Standard: Agreed upon measurements that stay the same wherever you go – Systems System: measurements that are all related – Customary System – based on body – Metric system – based on the Earth Most widely accepted standards in world

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What is the metric system? Created in France 1793 Scientists based the system on a meter – Meter means “measure” – Distance from equator to North Pole /10,000,000 Used all over the world US is only major country not to use – E.C. What are the only other two countries not to use metric system? Based on 10s

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Why the metric system? Scientists created and use the metric system – Science occurs all over the world – not just in USA – Scientists need to speak the same “language” when it comes to measurements We’re in science class The entire Earth (almost) uses the metric system – (The United States and two others) Business and trade uses metric system – Especially if they interact with foreign markets

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Quiz Length: – How many inches in a foot – How many feet in a yard? – How many yards in a mile? – How many inches in a mile? Volume: – How many teaspoons in a tablespoon? – How many tablespoons in a cup? – How many cups in a gallon?

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Quiz (continued) Mass: – How many ounces in a pound? – How many pounds in a ton? Temperature: – What is the freezing point of water? – What is the boiling point of water? Extra Credit: – What is a common equivalent for the following: (Choose 4) Fathom? Chain? Rod? Furlong? League? Peck?

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Extra Credit Extra Credit: – What is a common equivalent for the following: (Choose 4) Fathom? Chain? Rod? Furlong? League? Peck?

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Race??? SI (Metric) 1.5 m 2.75 m m m Customary (American) 1 1/2 ft 2 3/4 ft 3 1/3 ft + 4 5/8 ft

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And the Winner Is??? SI (Metric) m 2.75 m m m Customary (American) 2 1 1/2 ft = 1 12/24 2 3/4 ft = 2 18/24 3 1/3 ft = 3 8/ /8 ft = 4 15/ (53/24 = 2 5/24) 10 53/24 ( /24 = 12 5/24) 12 5/24

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Easier? The metric system is easier to use than our system – Only one base unit for each measurement Prefixes help with very large/small measurements – Based on 10’s Decimals not fractions – Faster – Very easy to add/subtract/multiply/divide Changing prefixes; just move decimal

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Comparison SI (Metric System) Units from Earth 1 unit with prefixes Based on 10s Decimals Faster Customary (American System ) Units from body Many units Based on 2s, 3s, 4s, 8s, 12s, 16s, 36s, etc. Fractions Slower

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Prefixes (mnemonic device) K H Da M D C M

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Prefixes K H Da M D C M King Harry Decked My Dad’s Creepy Monster

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Length Base unit – meter – Meter stick or metric ruler Smaller – decimeter – 10 decimeters = 1 meter – 1 decimeter (10-20)(40-50) Smaller yet – centimeter – 10 centimeters = 1 decimeter – 1 centimeter (11-12)(47-48) Smallest – millimeter – 10 millimeters = 1 centimeter – 1 millimeter (distance between tiny tick marks)

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Where do decimals come in? In between whole numbers – Between 4 and 5 cm – Write “4.” – Count the smaller unit (3 little tick marks) – Write the number after the decimal 4.3 cm

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Changing Prefixes Based on 10s Example 1 – 11.8 cm = ? mm – 11.8 cm x 10 mm = 11.8 x 10 = 118 mm 1 cm Example 2 – 4.65 m = ? mm

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Changing Prefixes Based on 10s Example 1 – 11.8 cm = ? m – 11.8 cm x 1 dm x 1 m = 11.8 = m 10 cm 10 dm 100 Example 2 – 4.65 m = ? km

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Additional Examples

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Length Summary Length: distance between two points Instrument: metric ruler / meter stick Base unit: meter (m) Accuracy: – Start at the “0” – Count accurately – Meter sticks end to end – Measure in a straight line

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Volume Summary Volume: amount of space an object takes up Instrument: graduated cylinder Base unit: liter (L) – 1 cm 3 = 1 mL Accuracy: – Know what you are counting by 0.5s, 1’s, 5s, – Keep graduated cylinder on flat surface – Measure to bottom of meniscus – Read meniscus at eye level

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Volume by Difference Measure volume of water – Easy to use number Add object to water Measure volume of water and object Subtract beginning volume from ending volume

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Mass Summary Mass: amount of matter in an object Instrument: triple beam balance Base unit: gram – 1 cm 3 water = 1 mL = 1 gram – 1 L = 1 kg Accuracy: – “Zero” triple beam balance before measuring – Carefully set object on pan – Keep triple beam balance on flat surface

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“Zero” Triple Beam Balance Clear off pan Move all riders to “0” Turn tare knob if pointer isn’t at “0”

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Mass by Difference Find mass of an object Change the object – Add to it – Take away from it Find the mass of the changed object Subtract smaller mass from larger mass

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Temperature Summary Temperature: amount of thermal (heat )energy in object Instrument: thermometer Base unit: degree Celsius (°C) Accuracy: – Know what you are counting by – Below “0” temperatures are “-” – Keep thermometer in middle of substance

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Graph Summary X-axis: horizontal axis (bottom) – Plot independent variable Independent variable: variable that you change / test Y-axis: vertical axis (side) – Plot dependent variable on Dependent variable: variable that you observe/measure

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Graph Summary (continued) Set-up your graph – Label your axes with variables and units – Label your axes with numbers Determine maximum value for each variable Count number of lines across & up and down Choose an easy number to count by (1s, 2s, 5s, 10s) Label only a few of the lines – Plot points (across, then up) – Connect dots with line (trend line) – Add title (include both variables)

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Safety Glassware: – Carry with two hands – Set it down carefully – Keep it in the middle of table Triple beam balances: – Carry with two hands – Set it down carefully – Keep it in the middle of the table Substances: – Don’t eat or drink (unless given permission)

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