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The Metric System and Units of Measurement

The Metric System and Units of Measurement. Units. After measuring a value, you MUST assign proper units!! “Walk five in that direction” means nothing until you provide a unit... meters, feet, etc. In science, we will use the Metric System or the SI system . The SI System of Measurement.

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The Metric System and Units of Measurement

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  1. The Metric System and Units of Measurement

  2. Units • After measuring a value, you MUST assign proper units!! • “Walk five in that direction” means nothing until you provide a unit... meters, feet, etc. • In science, we will use the Metric System or the SI system

  3. The SI System of Measurement • The SI System uses many prefixes to increase or decrease the size of the values • A KILOmeter is greater than a meter which is greater than a MILLImeter • The prefixes allow us to work with very large numbers or very small numbers while still working with manageable sized values.

  4. Units of Mass / Weight • Mass is NOT weight • Review: What is mass? What is weight?? • Mass uses units of grams, whiles weight is usually measured in pounds

  5. Concept Check • Name the quantity measured by each of the following SI units and give the SI symbol of the unit. • mole --- pascal • grams/millileter --- meter • second --- kilogram • kilograms/cubic meter --- Kelvins

  6. Concept Check • What is the difference between mass and weight. • What is the symbol and meaning of each prefix • milli- --- deci- • nano- --- centi-

  7. Calculations • Calculate the volume of a book that is 21 cm tall, 12 cm wide, and 3.5 cm thick • Calculate the density of a sample with a mass of 12.51 grams and a volume of 17.5 cm3

  8. Calculations • What is the percent error of a measurement with the experimental value of 18.99 grams and an accepted value of 15.890 grams?

  9. Specific Gravity • Specific Gravity is a comparison of the density of a substance with the density of a reference substance, usually at the same temperature. • This “reference substance” is usually _______. • Specific Gravity = density of substance (g/cm3) density of H2O (g/cm3)

  10. Specific Gravity • Specific Gravity = density of substance (g/cm3) density of H2O (g/cm3) • The specific gravity of a liquid can be measured using a device called a hydrometer • The density of H2O is 1.00g/cm3 (at room temp), making a substances’ specific gravity equal to its own density at room temp.

  11. Practice • How is density calculated? • What are the three equations relating mass, volume, and temperature?

  12. Practice • A weather balloon is inflated to a volume of 2.2x103 L with 37.4 grams of He. What is the density of the helium in g/L? • A plastic ball with a volume of 19.7cm3 has a mass of 15.8 g. What is the density? Would this ball sink or float in a container of gasoline (d=0.66g/cm3)

  13. Temperature Scales • The Temperature of an object determines the direction of heat transfer • Heat travels from ________ to ________. • All substances (except water) expand when heated and condense when cooled. What happens to the pressure??

  14. HEAT THEM UP, SPEED THEM UP!!!

  15. Temperature Scales • Fahrenheit • Celsius • Kelvin

  16. Conversion Equations ⁰F = (⁰C * 9/5 ) + 32 ⁰C = (⁰F – 32 ) * 5/9 K = ⁰C + 273.15K

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