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Density

Density. a physical property of matter. Property. = a characteristic that gives a substance identity. Properties of Vinegar: - clear liquid - strong odor - reacts with baking soda - acidic. Physical Properties.

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Density

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  1. Density a physical property of matter

  2. Property = a characteristic that gives a substance identity Properties of Vinegar: - clear liquid - strong odor - reacts with baking soda - acidic

  3. Physical Properties can be observed without changing the composition of the substance • Examples; • Color • Texture • Shape • Hardness • Buoyancy • Viscosity • Miscibility • Density

  4. DENSITY Styrofoam Brick Brick is more dense than Styrofoam because there is more mass packed into the same volume (more molecules or atoms in the same space.)

  5. Density Density can be defined as “unit massper unit volume” Density = Mass / Volume D = m / v

  6. Example: Density Density is a property of matter. If you measure the mass and the volume of an object, you can calculate it’s density using the formula: (g) (mL) D = m/v Density = mass/volume So, the units of density must be…. g/mL

  7. The Units for density come from this formula… • Why is density measured in g/mL? (aka “grams per milliliter”) (not “gee slash em-ell”) Because the formula for density is m mass(in grams) g D =----- = -------------------------- ---- v volume (in milliliters) mL

  8. Measurement

  9. Metric System Quantity Unit Unit Symbol Length meter m Mass gram g Volume liter L Time second s Temperature Kelvin or degree celsius K or o C

  10. Volume is special because: • Volume can be measured in liters (L), milliliters (mL), etc. s or…

  11. OR… • Volume can be measured in cubic meters (m3) centimeters (cm3), …..etc. Remember; 1 cm3 = 1 mL

  12. Remember this geometry? • Volume of a cube is …. l x w x h i.e. 4cm x 5cm x 2cm = 40cm3 • Volume of a cylinder is ….  r2 h i.e.  x (5cm)2 x 10cm = 250cm3

  13. Determining the Volume of an Irregularly Shaped Solid 32 mL 22 mL - ----------- 10 mL 32 mL 22 mL

  14. 1 cm3 = 1 mL Units of Density: • Mass is measured in g. • Volume is measured in mL or cm3. • Density is mass / volume, (g) / (mL) (g) / (cm3) ,so.. • density is measured in: • g/mL • or • g/cm3

  15. Mercury Aluminum DENSITY - an important and useful physical property Platinum 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3

  16. Atoms of some elements are more dense than others. Density of Gold: 19.30 g/mL Silver: 10.50 g/mL Aluminum:  2.70 g/mL

  17. SubstanceDensity (g/mL) • Air 0.0013 g/mL • Wood (Oak) 0.80 g/mL • Steel  7.80 g/mL • Water  1.00 g/mL

  18. Sample Problem • What is the density of 5.0 g of tin that has a volume of 1.2 mL? D = ? m = 5.0 g v = 1.2 mL D = m / v = 4.2 g/mL

  19. Steps for Solving Problems • Write the shopping list: • the unknown variable. (what’s the question asking for?) • all of the known variables. • 2. Write the formula you will be using. • 3. Calculate the final answer and include the units.

  20. Sample Problem • What is the density of 45.0 g of a liquid that has a volume of 62.5 mL? D = ? m = 45.0 g v = 62.5 mL D = m / v = g/mL

  21. m D v Variations of the Density Formula: D = m/v v = m/D m = v • D

  22. Sample Problem What is the volume of 21.0 g of tin? (Density of Tin = 4.2 g/mL) v = m / D v = v = ? D = 4.2 g/mL m = 21.0 g 5 mL

  23. Sample Problem What is the mass of 20 cm3 of tin? (Density of Tin = 4.2 g/mL) m = ? D = 4.2 g/mL v = 20 cm3 m = v D m = 84 g = 4.2 g/cm3 = 20 mL

  24. Review: 3 methods of measuring volume: • directly using glassware • geometry (e.g. l• w • h) • water displacement (vf – vi)

  25. Variations of the Density Formula: D = m/v v = m/D m = v • D

  26. 1. Write the unknown variable. 2.Write all the known variables. 3.Convert all variables to similar units. 4.Write formula you will be using. 5.Calculate: “Plug and Chug” 6.Circle your final answer with correct units.

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