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# Biology density

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Biology density

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• ROCKS - pass around
• Hot air balloon - Describe how a hot air balloon works. Defend your argument.
• Sinking vial - make it float
• Beans/ping pong ball; Big jug of water in a pool
• Air bladder when pulled up to quickly
• 250 b.c., the Greek mathematician Archimedes - story
• ### Biology density

1. 1. <ul><li>Density </li></ul>
2. 2. BW (Bell Work): Why does ice float in water? The Density of water is 1g/cm 3 .  An object will float is the density is less than 1.  An object will sink if its density is greater than 1.
3. 3. Description : A fish tank, Coke and Diet Coke are supplied. The Coke sinks while the Diet Coke floats.
4. 4. DENSITY <ul><li>Depends on: </li></ul><ul><ul><ul><li>Mass </li></ul></ul></ul><ul><ul><ul><li>Volume </li></ul></ul></ul><ul><ul><ul><li> D = m/v (g/cm 3 ) </li></ul></ul></ul><ul><ul><ul><li>Mass usually expressed in grams </li></ul></ul></ul><ul><ul><ul><li>Volume usually expressed in cm 3 or liters, etc. </li></ul></ul></ul>
5. 5. Density <ul><li>Density compares the mass of an object to its volume </li></ul><ul><li>D = mass = g or g </li></ul><ul><li> volume mL cm 3 </li></ul><ul><li>Note: 1 mL = 1 cm 3 </li></ul>
6. 6. <ul><li>What is density? </li></ul><ul><li>A material's density is defined as its mass per unit volume. </li></ul><ul><li>It is a measure of the mass of an object divided by its volume. </li></ul><ul><li>The principle of density was discovered by the Greek scientist Archimedes . </li></ul><ul><li>To calculate the density of an object, take the mass ( m ) and divide by the volume ( v ). This will give you the density in g/cm 3 . </li></ul>
7. 7. What would take up more space??? A kilogram of feathers….. or a kilogram of steel? OR
8. 8. “ Compactness” <ul><li>Density is essentially, a measurement of how tightly matter is crammed together. </li></ul>
9. 9. Gases <ul><li>How much kinetic energy do the molecules have?? </li></ul><ul><li>The greater the kinetic energy </li></ul><ul><li>…… the greater the volume </li></ul><ul><li>…… and the less dense that gas is!! </li></ul><ul><li>Therefore, cold air is more dense than warm air </li></ul><ul><li>Kinetic energy vs. potential energy </li></ul>Why is cold air denser than hot air?
10. 10. Gases <ul><li>Real life application….. </li></ul><ul><li>Low pressure weather system means warmer air tends to rise, </li></ul><ul><li>High pressure systems indicate a colder more dense air mass that will……. </li></ul><ul><li>SINK!!! </li></ul>
11. 11. Density Large ball – 0.53 g/cm 3 Medium ball – 1.05 g/cm 3 Small ball – 0.82 g/cm 3
12. 12. The “bounceability” of a ball depends on its density, not on its mass or on how big the ball is.
13. 13. Have you wondered why hot air balloons rise? When the air is heated, it becomes less dense until the balloon's total density is less than that of the atmosphere; A hot air balloon is literally floating on the denser, colder air.
14. 14. Do you know why volcanoes erupt? The main reason that magma rises to the surface to erupt at volcanoes is because it is less dense than the rocks that surround it.
15. 15. A ship floating on water is a great illustration of the difference between mass and density. A ship must have a density of less than 1.0 g/cm 3 (the density of water), or it will sink. Ships have a large mass, because they are made of steel, but because they have a large volume, their density is less than 1.0 g/cm 3 . If enough mass is added to them such that their density goes above 1.0 g/cm 3 , they will sink.
16. 16. You have a rock with a volume of 15cm 3 and a mass of 45 g. What is its density? D = m/v (g/cm 3 )
17. 17. What is the mass of a 350 cm 3 sample of pure silicon with a density of 2.336 g/cm 3 ? Mass = density x volume x Mass = 2.336 g/cm 3 x 350 cm 3 Mass = 818 grams D = m/v (g/cm 3 ) m=d x v v=m/d http://serc.carleton.edu/mathyouneed/densitysp.html
18. 18. Solving For Mass Original Formula   Multiply both sides by v                                                                      The &quot;v's&quot; cancel out                                                                Isolate for mass                                                                                       m = v x D
19. 19. solving For Volume Original Formula                 Multiply both sides by volume                                 m = v x D  Divide both sides by density                          Adjusted formula
20. 20. What would happen???? <ul><li>Mercury density = 13600kg/m 3 </li></ul><ul><li>Lead density = 11340kg/m 3 </li></ul>
21. 21. Lead floats on liquid mercury!
22. 22. Solids Ice vs. water…..
23. 23. SOLIDS <ul><li>Ice is less dense than water (which is why lakes and ponds have a thin layer of ice covering in winter, with water underneath) </li></ul><ul><li>Various rocks, woods, metals have a characteristic density specific to that substance </li></ul>Wouldn’t you like to have a bunch of THIS dense material?
24. 24. Factors affecting Density <ul><li>Temperature </li></ul><ul><li>Pressure </li></ul>
25. 25. Factors affecting Density <ul><li>Dissolved solids – in liquids </li></ul><ul><ul><ul><li>Concentration and kind of substances </li></ul></ul></ul>
26. 26. DETERMINING DENSITY <ul><li>Regular Shapes – mass, then determine the volume by formula </li></ul><ul><li>EX: cubes, cylinders, spheres, cones, etc. </li></ul><ul><li>Irregular shapes – mass, then measure displacement of a liquid (usually water) by that irregularly shaped object </li></ul>
27. 27. The densities for some common substances are: Substance Density (gm/cu.cm) Air 0.0013 Wood (oak) 0.85 Water 1.00 Ice 0.93 Aluminum 2.7 Lead 11.3 Gold 19.3 Ethanol 0.94 Methanol 0.79
28. 28. Volume Displacement (water displacement of Irregular shapes <ul><li>A solid displaces a matching volume of water when the solid is placed in water. </li></ul><ul><li> 33 mL </li></ul><ul><li>25 mL </li></ul>
29. 29. <ul><li>How are Submarines like fish…. </li></ul><ul><li>The swim bladder in bony fish control their relative density in order to rise or dive in the water….buoyancy </li></ul><ul><li>When air is added to the swim bladder, by diffusion through the blood vessels in the bladder walls, the fish becomes less dense overall </li></ul><ul><li>when air is removed fish become more dense </li></ul><ul><li>By changing the volume of air in the bladder, the fish’s density can be made equal to that of the surrounding water at a given depth. </li></ul>
30. 30. Home learning <ul><li>Make a Seven Layer Density Column </li></ul><ul><li>Seven Layer Density Column </li></ul><ul><li>Find some information about Archimedes' Principle . </li></ul><ul><li>What is Buoyancy? </li></ul>
31. 31. Archimedes and the Kings Crown
32. 32. Seven Layer Density Column
33. 33. Practice Problems <ul><li>1.You want to find the density of a small cube of an unknown material. It measures 1cmx1cmx2cm. It has a mass of 8g </li></ul><ul><li>2.You discover a gold bar while exploring an old shipwreck. It measures 10cmx5cmx2cm. It has a mass of 1,930g. Find the density. </li></ul><ul><li>3. A bar of soap measures 8cmx5cmx2cm. Its mass is 90g. Calculate its density. Predict whether this soap will float. </li></ul>http://www.fordhamprep.org/gcurran/sho/sho/worksheets/worksht27a.htm http://www.fordhamprep.org/gcurran/sho/sho/lessons/lesson27.htm
34. 34. Learning Check D1 <ul><li>Osmium is a very dense metal. What is its </li></ul><ul><li>density in g/cm 3 if 50.00 g of the metal occupies </li></ul><ul><li>a volume of 2.22cm 3 ? </li></ul><ul><li>1) 2.25 g/cm 3 </li></ul><ul><li>2) 22.5 g/cm 3 </li></ul><ul><li>3) 111 g/cm 3 </li></ul>
35. 35. Solution <ul><li>2) Placing the mass and volume of the osmium metal into the density setup, we obtain </li></ul><ul><li>D = mass = 50.00 g = </li></ul><ul><li> volume 2.22 cm 3 </li></ul><ul><li>= 22.522522 g/cm 3 = 22.5 g/cm 3 </li></ul>
36. 36. Learning Check <ul><li>What is the density (g/cm 3 ) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? </li></ul><ul><li>1) 0.2 g/ cm 3 2) 6 g/m 3 3) 252 g/cm 3 </li></ul><ul><li> 33 mL </li></ul><ul><li>25 mL </li></ul>
37. 37. Solution <ul><li>2) 6 g/cm 3 </li></ul><ul><li>Volume (mL) of water displaced </li></ul><ul><li>= 33 mL - 25 mL = 8 mL </li></ul><ul><li>Volume of metal (cm 3 ) </li></ul><ul><li>= 8 mL x 1 cm 3 = 8 cm 3 </li></ul><ul><li> 1 mL </li></ul><ul><li>Density of metal = </li></ul><ul><li> mass = 48 g = 6 g/cm 3 </li></ul><ul><li> volume 8 cm 3 </li></ul>
38. 38. Learning Check3 <ul><li>Which diagram represents the liquid layers in the cylinder? </li></ul><ul><li>(K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) </li></ul><ul><li>1) 2) 3) </li></ul>K K W W W V V V K
39. 39. Solution <ul><li>(K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) </li></ul><ul><li>1) </li></ul>K W V
40. 40. Density as Conversion Factors <ul><li>A substance has a density of 3.8 g/mL. </li></ul><ul><li>Density = 3.8 g/mL </li></ul><ul><li>Equality 3.8 g = 1 mL </li></ul><ul><li>Conversion factors. </li></ul><ul><li> </li></ul><ul><li>3.8 g and 1 mL </li></ul><ul><li> 1 mL 3.8 g </li></ul>
41. 41. Density Connections <ul><li>Mass Volume </li></ul><ul><li>kg L </li></ul><ul><li>g mL (cm 3 ) </li></ul><ul><li>mg </li></ul>
42. 42. Learning Check <ul><li>The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass, in kg, of 875 mL of octane? </li></ul><ul><li>1) 0.614 kg </li></ul><ul><li>2) 614 kg </li></ul><ul><li>3) 1.25 kg </li></ul>
43. 43. Solution <ul><li>1) 0.614 kg </li></ul><ul><li>Unit plan : mL  g  kg </li></ul><ul><li>Equalities : 1 mL = 0.702 g and 1 kg = 1000 g </li></ul><ul><li>Setup: </li></ul><ul><li>875 mL x 0.702 g x 1 kg = 0.614 kg </li></ul><ul><li> 1 mL 1000 g </li></ul><ul><li>density metric </li></ul><ul><li>factor factor </li></ul>
44. 44. Learning Check <ul><li>If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are given? </li></ul><ul><li>1) 0.548 L </li></ul><ul><li>2) 1.25 L </li></ul><ul><li>3) 1.83 L </li></ul>
45. 45. Solution <ul><li>1) </li></ul><ul><li>Unit Plan: g mL L </li></ul><ul><li>575 g x 1 mL x 1 L = 0.548 L </li></ul><ul><li>1.05 g 1000 mL </li></ul>
46. 46. Learning Check <ul><li>A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.0 pound of aluminum, how many liters of aluminum (D=2.70 g/cm 3 ) are obtained from the cans? </li></ul><ul><li>1) 1.0 L 2) 2.0 L 3) 4.0 L </li></ul>
47. 47. Solution <ul><li>1) 1.0 L </li></ul><ul><li>125 cans x 1.0 lb x 454 g x 1 cm 3 </li></ul><ul><li> 21 cans 1 lb 2.70 g </li></ul><ul><li>x 1 mL x 1 L = 1.0 L </li></ul><ul><li> 1 cm 3 1000 mL </li></ul>
48. 48. Learning Check <ul><li>You have 3 metal samples. Which one will displace the greatest volume of water? </li></ul><ul><li> 1 2 3 </li></ul><ul><li> </li></ul><ul><li>Discuss your choice with another student. </li></ul>25 g Al 2.70 g/mL 45 g of gold 19.3 g/mL 75 g of Lead 11.3 g/mL
49. 49. Solution <ul><li>1) 25 g Al x 1 mL = 9.2 mL 2.70 g </li></ul>25 g Al 2.70 g/mL
50. 50. Look at the graduated cylinder. It contains the following liquids. Label the liquids in the graduated cylinder based on the data below. (4 A . B . C D . Liquid Density (g/ml) corn syrup 1.38 ether 1.2 canola oil .93 salt water 1.1
51. 51. Put the following steps IN ORDER to demonstrate your understanding of how to find the density of an irregular object. <ul><li>1. _____a. Mass the object on a balance. </li></ul><ul><li>2. ____ b. Place object in graduated cylinder </li></ul><ul><li>3. _____c. Using the formula for density, calculate the density of </li></ul><ul><li>the object </li></ul><ul><li>4. _____d. Subtract initial volume from the volume of the object + </li></ul><ul><li>water </li></ul><ul><li>5. _____e. Fill graduated cylinder with water above the size of the </li></ul><ul><li>object </li></ul><ul><li>6. _____f. Include final units for mass and volume in final answer </li></ul><ul><li>7. _____g. Record initial volume in milliliters </li></ul><ul><li>8. _____h. Record mass in grams </li></ul><ul><li>9. _____i. Record volume of object only in milliliters </li></ul><ul><li>10. _____j. Record volume of object + water in milliliters </li></ul>
52. 52. RESOURCES <ul><li>http://www.middleschoolscience.com/dietcoke.htm (density Demo) </li></ul><ul><li>http://www.fordhamprep.org/gcurran/sho/sho/labs/densitylab.htm http://www.edinformatics.com/math_science/mvd_quiz.htm (MASS, VOLUME) </li></ul><ul><li>http://www.syvum.com/cgi/online/serve.cgi/members/gillilandd/quizzes/density.tdf (density problems) </li></ul>