Introduction to density
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Introduction to density

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I made these slides for a HS Chemistry course within my properties of matter unit while discussing intensive properties. After the slides, we discussed density demos (underwater volcano, candles in ...

I made these slides for a HS Chemistry course within my properties of matter unit while discussing intensive properties. After the slides, we discussed density demos (underwater volcano, candles in water and isopropyl, and liquid displacement of a gummy bear). Then, all students did a mini-lab: rainbow saltwater density straws. Homework was a density problem set.

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  • An intensive property that depends only on the composition of a substance, and not on the size of a sampleDensity can be used to identify substances
  • The next most expensive metal in the world is Osmium. In chemical element, it is symbolized with the level Os. It lays on the atomic number 76. Osmium is included in the family of Platinum. The quality of this metal is brittle, hard and available in blue color. This material usually is used to build an alloy. It can make such product become durable and sturdy.
  • For example, oil has a density of 0.85 g/cm3 and seawater has a density of 1.02 g/cm3. When these two liquids are mixed together, the denser seawater forms a layer underneath the less dense oil.
  • Bone density is done with a specialized x-ray machine (below). X-rays come up from below the patient and is detected by sensors in the arm over the patient. Bone density relates to bone strength. The condition of osteoporosis (porous bones) exhibits a lower density of the bone and makes bones more prone to breakage.
  • A real diamond will sink but a fake diamond such as moissanite will float in the solvent diiodomethane (CH2I2) which has a density of 3.33g/cm3.
  • Life Support in Space:  When sleeping, your warm breath is pushed upward and away from your face by the cooler more dense air in the room.  That way you don't keep breathing your own breath and suffocate.   However, in the weightlessness condition in a space craft, the air you breath out will stay close to your face, so you would suffocate unless you kept moving or if the air was circulated.   Gravity pulls more on the cool room air, which gets under and lifts up the warmer less dense air from the breath.  Without gravity that doesn't happen (hot air does not rise in zero gravity).  So spacecraft and places like the International Space Station must take that into consideration.   We take the affects of density for granted because we live in a gravity environment, but in a zero gravity environment some of the effects of density are simply not there.

Introduction to density Presentation Transcript

  • 1. W H A T D E T E R M I N E S T H E D E N S I T Y O F A S U B S T A N C E ? DENSITY
  • 2. Density Definition  The amount of matter in a given volume  “relative heaviness”  Intensive property  Density is constant for all sample size of a given substance Mass units: grams or kilograms Volume units: mL, L, or cm3 (solids)
  • 3. Density Calculation  Osmium is a very dense metal. If a piece of osmium has a mass of 50g and a volume of 2.22cm3, what is its density?
  • 4. Solve for Mass or Volume using the Formula Triangle
  • 5. At the Molecular Level
  • 6. Differences in density may help predict if an object sinks or floats (along with other forces such as buoyancy)
  • 7. Density of a Solid  Mass: balance (grams)  Volume: length x width x height= cm3 Phet Simulation Density of Cubes
  • 8. Density of an Irregular Solid  Mass: balance (grams)  Volume: Liquid displacement- the solid displaces (pushes away) a volume of water
  • 9. Density of a Liquid  Mass: balance (grams)  Volume: pour into graduated cylinder (mL)
  • 10. Applications  Density & Oil Spills  Oil (D= 0.85g/cm3) floats on the ocean surface (D= 1.02 g/cm3)  Clean-up techniques: skimming- machines that suck up oil like a vacuum cleaner
  • 11. Medical Uses  Bone density scan (X-rays): Bone density is related to bone strength, can diagnose osteoporosis, which makes bones more prone to breakage
  • 12. Identification  Diamond density is 3.5g/cm3, but Moissanite (a diamond simulant) is 3.21g/cm3
  • 13. Ocean Circulation Patterns
  • 14. Life Support in Space!  When sleeping, your warm breath is pushed upward and away from your face by the cooler, more dense air in the room  In space, hot air does not rise in zero gravity conditions, so need air circulation in International Space Station
  • 15. Rainbow Saltwater Density Straws: Mini-Lab Source: Steve Spangler