1 2.8 Density Density Calculations Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Density Compares the mass of an object to its volume Is the mass of a substance divided by its volume Density expression D liquids = mass = g or g = g/cm 3 volume mL cm 3 D solids = kg or kg = kg/L L m 3 Note: 1 mL = 1 cm 3 Density

Density calculation video 3

Review the steps for problems: 1.Circle information 2. DMV it 3. Put in triangle 4. Solve 5. Add units

5 Osmium is a very dense metal. What is its density in g/cm 3 if 50.0 g of osmium has a volume of 2 cm 3 ? 1) 2.5 g/cm 3 2) 25 g/cm 3 3) 100 g/cm 3 Learning Check

6 Given: mass = 50.0 g volume = 2 cm 3 Plan: Place the mass and volume of the osmium metal in the density expression. D = mass = 50.0 g volume2 cm 3 Calculator = 25 Final answer (2) = 25 g/cm 3 Solution

7 Volume by Displacement A solid completely submerged in water displaces its own volume of water. The volume of the solid is calculated from the volume difference mL mL = 9.5 mL = 9.5 cm 3 Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

8 Density Using Volume Displacement The density of the zinc object is then calculated from its mass and volume. mass = g = 7.2 g/cm 3 volume 9.5 cm 3 Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

9 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? 1) 0.17 g/cm 3 2) 6.0 g/cm 3 3) 380 g/cm mL 33.0 mL object Learning Check

10 Given: 48.0 g Volume of water = 25.0 mL Volume of water + metal = 33.0 mL Need: Density (g/mL) Plan: Calculate the volume difference. Change to cm 3, and place in density expression mL mL= 8.0 mL 8.0 mL x 1 cm 3 = 8.0 cm 3 1 mL Set Up Problem: Density = 48.0 g = 6.0 g = 8.0 cm 3 1 cm 3 Solution 6.0 g/cm 3

11 If olive oil has a density of 0.5 g/mL, how many milliliters of olive oil are in 18 g of olive oil? 1) 3.6 mL 2) 36 mL 3) 9 mL Learning Check

12 Given: D = 0.5 g/mL mass = 18 g Need: volume in liters Plan: Volume is mass divided by density Set Up Problem: 18 g x 1 mL = 0.5 g density factor Solution 36 mL

13 Which of the following samples of metals will displace the greatest volume of water? g of aluminum 2.70 g/mL 45 g of gold 19.3 g/mL 75 g of lead 11.3 g/mL Learning Check

14 1Plan: Calculate the volume for each metal and select the metal sample with the greatest volume. 1) 25g x 1 mL = 9.3 mL aluminum 2.70 g 2) 45 g x 1 mL = 2.3 mL gold 19.3 g 3) 75 g x 1 mL = 6.6 mL lead 11.3 g Solution 25 g of aluminum 2.70 g/mL

Problem 1 What is the density of an object with a mass of 60 g and a volume of 2 cm3?

Problem 1 What is the density of an object with a mass of 60 g and a volume of 2 cm3? Density= mass = 60g= volume 2 cm3 30 g/cm 3

Problem 2 If you have a rectangular gold brick that is 2 cm by 3 cm by 4 cm and has a mass of 48 g, what is its density?

Problem 2 If you have a rectangular gold brick that is 2 cm by 3 cm by 4 cm and has a mass of 48 g, what is its density? Volume= length x width x height 2 cm x 3 cm x 4 cm = Density= mass= 48 g = volume 24 cm3 24 cm 3 2 g/cm 3

Problem 3 If a block of wood has a density of 0.6 g/cm3 and a mass of 120 g, what is its volume?

Problem 3 If a block of wood has a density of 0.6 g/cm3 and a mass of 120 g, what is its volume? Volume= mass = 120 g = density 0.6 g/cm3 200 g/cm 3