Density final version
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The document defines density and describes how to calculate it using the equation density = mass/volume. Density is a measure of how concentrated a substance is and has units of mass/volume (e.g. g/mL). Examples show how to use the density equation to calculate density, mass, or volume by rearranging the terms. Practice problems demonstrate calculating density, mass, and volume for different substances using the given values and density equation.
Density final version
- 1. Density By Shawn P. Shields, Ph. D. This work is licensed by Shawn P. Shields-Maxwell under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
- 2. First, A Bit About Units… Mass is generally defined as the amount of matter contained in an object. Mass can be thought of as “weight,” although they are not technically the same. See the link below for a discussion of the difference.* The SI unit for mass is the kilogram (kg) In this course, we will often use “grams” (g). (1 kg = 1000 g) Volume is the 3D space occupied by an object. The SI unit for volume is the liter (L) *NOTE: This concept will not be tested. Mass vs Weight: http://en.wikipedia.org/wiki/Mass_versus_weight
- 3. Density (d) Defined as the mass per unit volume of a substance Units commonly used in density calculations are Mass (m) in grams Volume (V) in mL or “cubic centimeters (cm3)” or “cc” 1 mL = 1 cm3 The equation for density is 𝑑 = mass volume Practice rearranging this equation to solve for density, mass, or volume d m V
- 4. Density Calculation Example Calculate the density of a piece of graphite with a mass of 50.0 grams and a volume of 22.4 cm3. Be sure to include the units in your answer!
- 5. Density Calculation Solution Calculate the density of a piece of graphite with a mass of 50.0 grams and a volume of 22.4 cm3. Be sure to include the units in your answer! Solution: First, identify what information you are given in the problem. 𝑑 = mass volume
- 6. Density Calculation Solution Calculate the density of a piece of graphite with a mass of 50.0 grams and a volume of 22.4 cm3. Be sure to include the units in your answer! Solution: First, identify what information you are given in the problem. Then, plug in the given values into the density equation and solve. 𝑑 = mass volume = 50.0 g 22.4 cm3 = 2.23 g cm3
- 7. Density Calculation Example 2 Isopropyl alcohol has a density of 0.785 g/mL at 25C. How much mass is contained in a 150 mL sample of this alcohol? Be sure to include the units in your answer!
- 8. Density Calculation Solution Isopropyl alcohol has a density of 0.785 g/mL at 25C. How much mass is contained in a 150 mL sample of this alcohol? Be sure to include the units in your answer! Solution: First, identify what information you are given in the problem. 𝑑 = mass volume
- 9. Density Calculation Solution Isopropyl alcohol has a density of 0.785 g/mL at 25C. How much mass is contained in a 150 mL sample of this alcohol? Be sure to include the units in your answer! Solution: First, identify what information you are given in the problem. Next, rearrange the density equation to solve for mass (m). (Use the triangle) m = density × volume d m V 𝑑 = mass volume
- 10. Density Calculation Solution Isopropyl alcohol has a density of 0.785 g/mL at 25C. How much mass is contained in a 150 mL sample of this alcohol? Be sure to include the units in your answer! Solution: First, identify what information you are given in the problem. Next, rearrange the density equation to solve for mass (m). Then, plug in the given values into the rearranged density equation and solve. m = density × volume = 0.785 g mL × 150 mL m = 0.785 g mL × 150 mL = 117.75 g Sig figs! m = 120 g
- 11. Density Calculation Mini Quiz A tablet of aspirin has a density of 1.40 g/cm3 at 25C. What is the volume of a 3.90 g aspirin tablet? Be sure to include the units in your answer!
- 12. Density Calculation Mini Quiz Solution A tablet of aspirin has a density of 1.40 g/cm3 at 25C. What is the volume of a 3.90 g aspirin tablet? Be sure to include the units in your answer! Solution: First, identify what information you are given in the problem. 𝑑 = mass volume
- 13. Density Calculation Mini Quiz Solution A tablet of aspirin has a density of 1.40 g/cm3 at 25C. What is the volume of a 3.90 g aspirin tablet? Be sure to include the units in your answer! Solution: First, identify what information you are given in the problem. Next, rearrange the density equation to solve for volume (V). (Use the triangle) d m V 𝑑 = mass volume volume = mass 𝑑
- 14. Density Calculation Mini Quiz Solution A tablet of aspirin has a density of 1.40 g/cm3 at 25C. What is the volume of a 3.90 g aspirin tablet? Be sure to include the units in your answer! Solution: First, identify what information you are given in the problem. Next, rearrange the density equation to solve for mass (m). Then, plug in the given values into the rearranged density equation and solve. Sig figs! V = 2.79 cm3 volume = mass 𝑑 = 3.90 g 1.40 g cm3 = 2.7857 cm3