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### Transcript of "2 8 density"

1. 1. <ul><li>2.8 </li></ul><ul><li>Density </li></ul>Chapter 2 Measurements Basic Chemistry Copyright © 2011 Pearson Education, Inc. Objects that sink in water are more dense than water; objects that float in water are less dense.
2. 2. <ul><li>Density </li></ul><ul><li>compares the mass of an object to its volume </li></ul><ul><li>is the mass of a substance divided by its volume </li></ul><ul><li>Density expression : </li></ul><ul><li>D = mass = g or g = g/cm 3 </li></ul><ul><li> volume mL cm 3 </li></ul><ul><li>Note: 1 mL = 1 cm 3 </li></ul>Density Basic Chemistry Copyright © 2011 Pearson Education, Inc.
3. 3. Guide to Calculating Density Basic Chemistry Copyright © 2011 Pearson Education, Inc.
4. 4. Densities of Common Substances Basic Chemistry Copyright © 2011 Pearson Education, Inc.
5. 5. <ul><li>Osmium is a very dense metal. What is its </li></ul><ul><li>density, in g/cm 3 , if 50.0 g of osmium has a </li></ul><ul><li>volume of 2.22 cm 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>Learning Check Basic Chemistry Copyright © 2011 Pearson Education, Inc.
6. 6. <ul><li>STEP 1 Given 50.0 g; 22.2 cm 3 </li></ul><ul><li> Need density, in g/cm 3 </li></ul><ul><li>STEP 2 Plan Write the density expression. </li></ul><ul><li> D = mass </li></ul><ul><li> volume </li></ul><ul><li>STEP 3 Express mass in grams and volume in cm 3 </li></ul><ul><li> mass = 50.0 g volume = 22.2 cm 3 </li></ul><ul><li>STEP 4 Set up problem </li></ul><ul><li> D = 50.0 g = 22.522522 g/cm 3 </li></ul><ul><li> 2.22 cm 3 </li></ul><ul><li> = 22.5 g/cm 3 (3 SF) </li></ul>Solution Basic Chemistry Copyright © 2011 Pearson Education, Inc.
7. 7. Volume by Displacement <ul><li>A solid completely submerged in water displaces its own volume of water. </li></ul><ul><li>The volume of the solid is calculated from the volume difference. </li></ul><ul><li>45.0 mL - 35.5 mL </li></ul><ul><li> = 9.5 mL = 9.5 cm 3 </li></ul>The density of a solid is determined from its mass and the volume it displaces when submerged in water. Basic Chemistry Copyright © 2011 Pearson Education, Inc.
8. 8. Density Using Volume Displacement <ul><li>The density of the object is </li></ul><ul><li>calculated from its mass and </li></ul><ul><li>volume. </li></ul><ul><li>mass = 68.60 g = 7.2 g/cm 3 </li></ul><ul><li>volume 9.5 cm 3 </li></ul>Basic Chemistry Copyright © 2011 Pearson Education, Inc.
9. 9. <ul><li>What is the density (g/cm 3 ) of 48.0 g of a metal if the level of water in a graduated cylinder rises from 25.0 mL to 33.0 mL after the metal is added? </li></ul><ul><li>1) 0.17 g/cm 3 2) 6.0 g/cm 3 3) 380 g/cm 3 </li></ul><ul><li>25.0 mL 33.0 mL </li></ul><ul><li> object </li></ul>Learning Check Basic Chemistry Copyright © 2011 Pearson Education, Inc.
10. 10. <ul><li>STEP 1 Given 48.0 g volume of water = 25.0 mL </li></ul><ul><li> volume of water + metal = 33.0 mL </li></ul><ul><li> Need Density (g/mL) </li></ul><ul><li>STEP 2 Plan Calculate the volume difference, change unit to cm 3 , and place in density expression. </li></ul><ul><li>STEP 3 Express mass in grams and volume in cm 3 volume of solid = 33.0 mL - 25.0 mL = 8.0 mL </li></ul><ul><li>8.0 mL x 1 cm 3 = 8.0 cm 3 </li></ul><ul><li>1 mL </li></ul><ul><li>STEP 4 Set Up Problem </li></ul><ul><li> Density = 48.0 g = 6.0 g = 6.0 g/cm 3 </li></ul><ul><li> 8.0 cm 3 1 cm 3 </li></ul>Solution Basic Chemistry Copyright © 2011 Pearson Education, Inc.
11. 11. Sink or Float <ul><li>Ice floats in water because the density of ice is less than the density of water. </li></ul><ul><li>Aluminum sinks because its density is greater than the density of water. </li></ul>Basic Chemistry Copyright © 2011 Pearson Education, Inc. Objects that sink in water are more dense than water.
12. 12. <ul><li>Which diagram correctly represents the liquid layers in the cylinder? Karo (K) syrup (1.4 g/mL), vegetable (V) oil (0.91 g/mL), water (W) (1.0 g/mL) </li></ul><ul><li>1 2 3 </li></ul>Learning Check W W K K K V V V W Basic Chemistry Copyright © 2011 Pearson Education, Inc.
13. 13. <ul><li>1) </li></ul><ul><li>vegetable oil 0.91 g/mL </li></ul><ul><li>water 1.0 g/mL </li></ul><ul><li> Karo syrup 1.4 g/mL </li></ul>Solution K W V Basic Chemistry Copyright © 2011 Pearson Education, Inc.
14. 14. <ul><li>For a density of 3.8 g/mL, </li></ul><ul><li>an equality is written as </li></ul><ul><li>3.8 g = 1 mL </li></ul><ul><li>and two conversion factors are written as </li></ul><ul><li>Conversion 3.8 g and 1 mL </li></ul><ul><li>factors 1 mL 3.8 g </li></ul><ul><li> </li></ul>Density as a Conversion Factor Basic Chemistry Copyright © 2011 Pearson Education, Inc.
15. 15. Guide to Using Density Basic Chemistry Copyright © 2011 Pearson Education, Inc.
16. 16. <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>Learning Check Basic Chemistry Copyright © 2011 Pearson Education, Inc.
17. 17. <ul><li>1) 0.614 kg </li></ul><ul><li>STEP 1 Given D = 0.702 g/mL; V= 875 mL </li></ul><ul><li> Need mass in kg of octane </li></ul><ul><li>STEP 2 Plan mL  g  kg </li></ul><ul><li>STEP 3 Equalities </li></ul><ul><li> 0.702 g = 1 mL 1 kg = 1000 g </li></ul><ul><li>STEP 4 Set Up Problem </li></ul><ul><li>875 mL x 0.702 g x 1 kg = 0.614 kg (1) </li></ul><ul><li> 1 mL 1000 g </li></ul><ul><li> density metric </li></ul><ul><li> factor factor </li></ul>Solution Basic Chemistry Copyright © 2011 Pearson Education, Inc.
18. 18. <ul><li>If olive oil has a density of 0.92 g/mL, how many liters of olive oil are in 285 g of olive oil? </li></ul><ul><li>1) 0.26 L </li></ul><ul><li>2) 0.31 L </li></ul><ul><li>3) 310 L </li></ul>Learning Check Basic Chemistry Copyright © 2011 Pearson Education, Inc.
19. 19. <ul><li>2) 0.31 L </li></ul><ul><li>STEP 1 Given D = 0.92 g/mL mass = 285 g </li></ul><ul><li> Need volume in liters </li></ul><ul><li>STEP 2 Plan g mL L </li></ul><ul><li>STEP 3 Equalities 1 mL = 0.92 g 1 L = 1000 mL </li></ul><ul><li>STEP 4 Set Up Problem </li></ul><ul><li> 285 g x 1 mL x 1 L = 0.31 L </li></ul><ul><li> 0.92 g 1000 mL </li></ul><ul><li>density metric </li></ul><ul><li> factor factor </li></ul>Solution Basic Chemistry Copyright © 2011 Pearson Education, Inc.
20. 20. <ul><li>Which of the following samples of metals will displace the greatest volume of water? </li></ul><ul><li>1 2 3 </li></ul><ul><li> </li></ul>Learning Check 25 g of aluminum 2.70 g/mL 45 g of gold 19.3 g/mL 75 g of lead 11.3 g/mL Basic Chemistry Copyright © 2011 Pearson Education, Inc.
21. 21. <ul><li>1) </li></ul><ul><li>Plan: Calculate the volume for each metal and select </li></ul><ul><li>the metal sample with the greatest volume. </li></ul><ul><li>1) 25 g x 1 mL = 9.3 mL aluminum 2.70 g </li></ul><ul><li>2) 45 g x 1 mL = 2.3 mL gold 19.3 g </li></ul><ul><li>3) 75 g x 1 mL = 6.6 mL lead 11.3 g </li></ul>Solution 25 g of aluminum 2.70 g/mL Basic Chemistry Copyright © 2011 Pearson Education, Inc.
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