Why are these important?

 SI stands for Systeme International d’Unites  Internationally, this is the system that we will use measure anything in science.  There are several things that get measured  Length, Mass, Volume/Area, Density, Time, Temperature

 Measured in Meters (m)  How long something is or the distance between two objects

 Measured in grams (g)  The amount of matter in an object  Not the same as weight but similar

 Area is measured in m 2  It is the amount of space on the surface something takes up.  Volume is measured in the liter (L) or m 3  Amout of space something takes in 3D

 When measuring from a graduated cylinder or a beaker, measure at the bottom of the meniscus (natural curve that water makes in a container)

 Amount of matter that occupies a given space  Doesn’t have a special unit to itself.  Labeled g/mL or g/cm3  Aka mass/volume  No tool to measure

 Internationally time is measured by seconds (s)  Usually is going to be measured by a watch or a timer

 In science we do no use the Fahrenheit scale. We use Celcius (C°)  We could also measure in Kelvin but that’s less important at the moment  Use a thermometer

 Unit is whatever you are measuring in. It is described as any of the SI measurements that are used  Denoted with a u

 There are bigger and smaller units of each base units  Length-meter(m)  Mass- gram (g)  Volume- Liter (L)  Time- second (s)  Temperature- Celcius (C°)  Prefixes will go in front of the base unit.  Prefixes are: kilo-, hecto-, deka-, deci-, centi-, milli-, micro-, nano-, pico-  King Henry Doesn’t [Usually] Drink Chocolate Milk

 Kilo(k)- kilogram (kg), kilometer (km), kiloliter (kL), kilosecond (ks), kilounit (ku) 1ku= 1000 u (1000 of your base unit)  1u=.001 ku  Hecto(h)- hectogram (hg), hectometer (hm), hectoliter (hL), hectosecond (hs), hectounit (hu) 1 hu= 100 u (100 of your base unit)  1 u=.01 hu

 Deka(D)- dekagram (Dg), dekameter (Dm), dekaliter (DL), dekasecond (Ds), dekaunit (Du)  1Du= 10 u (10 of your base unit)  1 u=.1 Du

 Deci(d)- decigram (dg), decimeter (dm), deciliter (dL), decisecond (ds), deciunit (du)  1 u= 10 du (10 du in your base unit)  1du =.1u  Centi (c)- centigram (cg), centimeter (cm), centiliter (cL), centisecond (cs), centiunit (cu)  1 u= 100 cu (100 cu in your base unit)  1cu=.01 u

 Milli (m)- milligram (mg), millimeter (mm), milliliter (mL), millisecond (ms), milliunit (mu)  1 u= 1000 mu (1000 mu in your base unit)  1 mu=.001 u  Quick Review….

 1 m = ? mm  1ms= ? s  1 L = ? cL = ? mL  1 L = ? mm  HINT!  If you are getting bigger divide.  If you are getting smaller multiply

 Accuracy- is a measure of how close a measurement comes to the actual value of whatever is measured.  Ex. Darts land close to the bull’s-eye

 Precision- the measure of how close a series of measurements are to one another  Ex. The darts are all very closely grouped together. (Don’t have to be near bull’s-eye)  If something is precise it isn’t always accurate.

 The density of a certain metal is 2.45 g/mL.  You measure densities of 2.01 g/mL, 1.99 g/mL and 2.03 g/mL. Accurate, precise, or both?  You measure densities of 2.45 g/mL, 2.50 g/mL, and 2.47 g/mL. Accurate, precise, or both?  You measure densities of 1.57 g/mL, 3.01 g/mL, and 2.45 g/mL

 Accepted value- The correct value based on reliable references  Experimental value- The value measured in the lab

 Error is the difference between the experimental value and the accepted value.  Error= experimental value- accepted value  The density of gold is g/mL. You do a experiment and find a density for gold of g/mL. What is the error in your experiment?

 Error can be positive or negative depending on whether the experimental value is great than or less than the accepted value.  Percent error is the absolute value of the error divided by the accepted value, multiplied by 100%.  Percent error= error/(accepted value) x 100%  Gold PE = 1.20(g/mL)/19.30(g/mL)x 100%  Gold PE = 6.21%

 In many branches of science, some numbers are very small, while others are quite large. To convieniently express these numbers, scientists use a short hand called scientific notation.  Expresses a number as a multiplier and power of 10.  If the decimal point is shifted right the power of 10 is negative  If the decimal point is shifted to the left, the power of 10 is positive.

 I’m passing out a sheet. This is my reminder to myself… Don’t laugh at me