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SI Units In science, we need to speak the same language

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Presentation on theme: "SI Units In science, we need to speak the same language"— Presentation transcript:

1 SI Units In science, we need to speak the same language 1795 1960
French scientists develop metric system 1960 International committee meets to update the system and names it the “Systeme Internationale d’Unites” aka SI

2 SI Base Units Seven SI base units Base unit
A defined unit in a system of measurement that is based on an object or event in the physical world

3 Tools of the Trade Mass Scale that measures GRAMS not POUNDS
Pounds are used to measure the force of gravity on your mass…we want to measure the amount of STUFF (Matter) in a thing Temperature thermometer measures the kinetic energy (KE) /movement of particles Faster moving particle=more (KE)=higher temp (HOT) Slower moving particles=less (KE)=cooler temp (COLD) Volume amount of space object takes up… ruler, measuring tape, etc to measure meters3 (l x w x h) OR graduated cylinder to measure LITERS Measure volume at the MENISCUS (curve or dip in the water)

4 SI Derived Units Not all quantities can be measured with base units
More than one base unit can be used Speed limit is measure in…. MPH Miles per hour Which is a combo of what base units? Length and time

5 Derived Units

6 Common derived units we will use
Speed Base unit of length and base unit of time Meters/second Volume 3 base units of length Length x length x length 1 cm3 = 1 mL Density Mass/volume Ratio that compares mass of an object to its volume g/cm3 or g/mL

7 Density Density=mass divided by the volume
D=m/V Gram/L or grams/m3 How do we figure out volume of odd shaped objects…say a paper clip? Water Displacement What happens when you fill up the bath tub to the rim and then get in?

8 Archimedes Principle Measure known amount of water in graduated cylinder and record VOLUME (mL) This is initial volume (Vi) Drop in odd shaped object (paper clip) Record the NEW volume of water This is final vlume (Vf) Subtract Vi from Vf to get volume of object (Vo) Vo = Vf- Vi Get the mass of the paper clip form the scale Plug the mass (g) and volume (L) into density formula to figure out the density of the paper clip

9 Prefixes Used with SI units

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12 Temperature SI unit? Our thermometers measure Celsius
Kelvin Our thermometers measure Celsius To convert from Celsius to Kelvin 0o C = 273 K To convert from Kelvin to Celsius 373 K = 100o C


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