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Understanding the International System of Units (SI)

Learn about conversions, units, and quantities in the metric system. Understand length, volume, mass, weight, temperature, and density. Practice calculations and understand the concept of unit cancellation. Discover how density affects floating and sinking in fluids.

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Understanding the International System of Units (SI)

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  1. The International System of Units www.assignmentpoint.com

  2. Based on the #10 • Makes conversions easier • Old name = metric system www.assignmentpoint.com

  3. Units and Quantities • Length – the distance between 2 points or objects Base unit = meter • Volume – the space occupied by any sample of matter V = length x width x height Base unit = liter Based on a 10cm cube (10cm x 10cm x 10cm = 1000cm3) 1 liter = 1000cm3 www.assignmentpoint.com

  4. Mass – the amount of matter contained in an object Base unit = gram Different than weight… Weight - a force that measures the pull of gravity www.assignmentpoint.com

  5. www.assignmentpoint.com

  6. Temperature – a measure of the energy of motion How fast are the molecules moving? When 2 objects are at different temperatures heat is always transferred from the warmer → the colder object www.assignmentpoint.com

  7. Temperature Scales • Celsius scale – Freezing point of H2O = 0oC Boiling point of H2O = 100oC • Kelvin scale – Freezing point of H2O = 273.15K Boiling point of H2O = 373.15K K = C + 273 C = K - 273 www.assignmentpoint.com

  8. Temperature Scale Conversions www.assignmentpoint.com

  9. Conversion FactorsandUnit Cancellation www.assignmentpoint.com

  10. A physical quantity must include: Number + Unit www.assignmentpoint.com

  11. 1 foot = 12 inches www.assignmentpoint.com

  12. 1 foot = 12 inches 1 foot =1 12 inches www.assignmentpoint.com

  13. 1 foot = 12 inches 1 foot =1 12 inches 12 inches =1 1 foot www.assignmentpoint.com

  14. 1 foot 12 inches 12 inches 1 foot “Conversion factors” www.assignmentpoint.com

  15. 1 foot 12 inches 12 inches 1 foot “Conversion factors” How many inches are in 3 feet? 12 inches ( ) ( ) =36 inches 3 feet 1 foot www.assignmentpoint.com

  16. 100 cm ______ 100 cm 1 m ______ 1 m 1 m 100 cm ______ 132 cm ( ) equality: 1 m = 100 cm conversion factors: How many cm are in 1.32 meters? or X cm = 1.32 m = We use the idea of unit cancellation to decide upon which one of the two conversion factors we choose. www.assignmentpoint.com

  17. 0.0872 m 100 cm ______ 1 m ______ 1 m 100 cm ______ ( ) 1 m 100 cm equality: 1 m = 100 cm conversion factors: How many meters is 8.72 cm? or X m = 8.72 cm = Again, the units must cancel. www.assignmentpoint.com

  18. 1 ft ______ 1 ft 12 in 12 in ( ) 12 in ______ ____ 1 ft 3.28 ft equality: 1 ft = 12 in How many feet is 39.37 inches? conversion factors: or X ft = 39.37 in = Again, the units must cancel. www.assignmentpoint.com

  19. 1 km 1,000 m ( ) ______ ( ) ____ 1 m 10 dm 1.5 km How many kilometers is 15,000 decimeters? X km = 15,000 dm = www.assignmentpoint.com

  20. ( ) _____ 60 min 1 h 378,432 s ( ) ( ) ____ 60 s 3.78 x 105 s ____ 24 h 1 min 1 d How many seconds is 4.38 days? X s = 4.38 d = If we are accounting for significant figures, we would change this to… www.assignmentpoint.com

  21. Why do some objects float in water while others sink? • Need to know the ratio of the mass of an object to it’s volume • Pure H2O at 4oC = 1.000g/cm3 • If an object has a lower ratio it will float • If an object has a greater ratio it will sink www.assignmentpoint.com

  22. Density • The ratio of an object’s mass to it’s volume Density = mass volume Example: A 10.0cm3 piece of lead has a mass of 114g. What is the density of lead? 114g = 10.0cm3 11.4g/cm3 www.assignmentpoint.com

  23. Recall… What type of property is density? Does the density of a material change in relation to the sample size? NO… density is an Intensive property it depends only on the composition of the material www.assignmentpoint.com

  24. What might affect a substance’s density? • Temperature • The volume of most substances ↑ with an ↑ in temperature • the mass remains the same If the volume increases… what affect does it have on a substance’s density? The density decreases *Exception – Water’s volume ↑ with a ↓ in temperature Its density decreases & ice floats H2O www.assignmentpoint.com

  25. M V D Calculating Density What is the volume of a pure silver coin that has a mass of 14g, and a density of 10.5g/cm3? D = 10.5g/cm3 M = 14g V = ? Rearrange the density formula to solve for V www.assignmentpoint.com

  26. g g V = M D V = 14g = 14 x 1 cm3= 10.5g/cm3 10.5 1.3cm3 www.assignmentpoint.com

  27. M V D cm3 cm3 What is the mass of mercury that has a density of 13.5g/cm3 and a volume of 0.324cm3? Once again, rearrange the density formula… and solve for M. M = D x V = 4.62g M = 13.5g x 0.342 www.assignmentpoint.com

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