# SI (Système International d’unités)

## Presentation on theme: "SI (Système International d’unités)"— Presentation transcript:

SI (Système International d’unités)
Metric System

Introduction The thermometer says 39°C. Your school is 2 km away.
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?

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

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

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

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

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

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

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

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

Quiz Length: Volume: 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?

Quiz (continued) Mass: Temperature: Extra Credit:
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?

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

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

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

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

Comparison SI (Metric System) Units from Earth 1 unit with prefixes
Customary (American System ) Units from Earth 1 unit with prefixes Based on 10s Decimals Faster Units from body Many units Based on 2s, 3s, 4s, 8s, 12s, 16s, 36s, etc. Fractions Slower Metric units from distance of equator to North pole / 10,000,000 American units from the foot, width of finger, outstretched arms, double paces, etc. Meter, Liter, Gram Inches, Feet, Yards, Miles (Rod, Furlongs, Fathoms, Chains, etc.) Ounces, teaspoons, Tablespoons, Pints, Quarts, Cups, Gallons, Barrels, (hogs head, gil, dram, jigger) Ounces, Pound, Ton, (grain, dram) Everything is based on 10 – How many ____ in a ____? Inches in a foot? Feet in a yard? Feet in a mile? Yards in a mile? Ounces in a cup? Cups in a quart? Quarts in a gallon? Ounces in a pound? Pounds in a ton? Because it is based on 10s – you use decimals (tenths, hundredths, etc) American system is not based on 10s and we usually use fractions, 17/64, ½, ¼, etc Because you use decimals much faster – race (

Prefixes (mnemonic device)
K H Da M D C

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

Length Base unit – meter Smaller – decimeter Smaller yet – centimeter
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)

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

Changing Prefixes Based on 10s Example 1 Example 2 11.8 cm = ? mm
11.8 cm x 10 mm = 11.8 x 10 = 118 mm 1 cm Example 2 4.65 m = ? mm 4.65 x 10 x 10 x 10 = 4.65 x 1000 = 4650

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

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

Volume Summary Volume: amount of space an object takes up
Instrument: graduated cylinder Base unit: liter (L) 1 cm3 = 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

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

Mass Summary Mass: amount of matter in an object
Instrument: triple beam balance Base unit: gram 1 cm3 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

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

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

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

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

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)

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