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Density

Density. It’s not just about weight anymore…. Learning Goal. Relate the arrangement of subatomic particles in a substance to its density and observable macroscopic behavior. How close the atoms or molecules are to each other

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Density

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  1. Density It’s not just about weight anymore…

  2. Learning Goal Relate the arrangement of subatomic particles in a substance to its density and observable macroscopic behavior.

  3. How close the atoms or molecules are to each other More than “heaviness” - density includes how much space an object takes up!! All substances have density including liquids, solids, and gases Density is the measure of the “compactness” of a material

  4. “Compactness” Less dense More dense

  5. Gases • Least ‘compact’ of the phases of matter • Warm gases are less dense than cold gases – one reason for how weather works

  6. LIQUIDS • Molecules are close together but can move past each other • Colder liquids are denser than warm liquids • water at 50oC (120oF): 0.9880 g/mL • water at 40oC (104oF): 0.9923 g/mL • water at 30oC (86oF): 0.9956 g/mL • water at 20oC (68oF): 0.9982 g/mL • water at 10oC (50oF): 0.9997 g/mL • Cold water in lakes tend to sink (this creates a constant mixing of water, nutrients, and other substances)

  7. LIQUIDS • The more dissolved solids in a solution, the more dense • pure water (0% salt) = 1.00 g/mL • 15% salt water = 1.11 g/mL • 25% salt water = 1.19 g/mL Color added to show layers Coffee creamer is denser than coffee

  8. SOLIDS • The most ‘compact’ of the phases of matter.

  9. What would happen???? • Mercury density = 1.3600 g/cm3 • Lead density = 1.1340 g/cm3 Mercury is a liquid metal at room temperature. Lead is a solid at room temperature. Pool balls are made of lead. Would lead sink or float in mercury?

  10. Lead floats on liquid mercury!

  11. Explain these in your notebook Why do the bubbles rise out of the water? egg

  12. Water is very unique…can you explain its behavior below? Solid water (ice) Liquid water

  13. Combination materials If you combine phases, you can get interesting densities: • Styrofoam (solid plastic with air bubbles inside): 0.35 g/cm3 • Whipped cream (liquid with air bubbles): 0.50 g/cm3

  14. Connecting macroscopic to sub microscopic

  15. Connecting macroscopic to sub microscopic Least to most dense: helium: 0.0001785 g/cm3 • fluorine: 0.001696 g/cm3 • It’s formula is F2! water: 1.00 g/cm3 magnesium: 1.74 g/cm3 NaCl: 2.16 g/cm3

  16. Learning Goal Using the mathematical definition of density, compare the densities of regular and irregular objects using their masses and volumes. A BIG Idea: Density is an intensive property. It is built into the substance due to the compactness of the atoms. Any size, any shape: aluminum is still 2.70 g/cm3 If an object’s density is 2.70 g/cm3, it MUST be aluminum

  17. Learning Goal Density is the amount of mass in a space. So, Density = mass / volume • Jack has a shiny object. It has a mass of 6.35g and a volume of 2.35 cm3. What is the density of the object? What is it made of? • Jill has a gel pen. The gel pen has a mass of 8.30g and a volume of 2.00cm3. What is the density of the pen?

  18. Learning Goal Density is the amount of mass in a space. So, Density = mass / volume • Jack has a shiny object. It has a mass of 6.35g and a volume of 2.35 cm3. What is the density of the object? What is it made of? 2.70 g/cm3, made of aluminum • Jill has a gel pen. The gel pen has a mass of 8.30g and a volume of 2.00cm3. What is the density of the pen? • 4.15 g/cm3

  19. Learning Goal Try one of the videos on the plan to see how to determine densities in the lab….. Then try some Ways to Practice and Extend Your Learning (also on the plan).

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