1. Density Type of Units, Formula, Solving Density Problems

2. Density as a Derived Unit Why is it easier to lift a grocery bag full of paper goods than it is to lift a grocery bag full of soup cans? Volume of grocery bag full of paper goods = Volume of grocery bag full of soup cans The difference in effort to lift the grocery bags must be related to how much mass is packed into the same volume. Density is a ratio that compares the mass of an object to its volume. The units are often g/mL or g/cm 3. Thus, density is a derived unit: a combination of base units.

3. The Density Formula The Density T-Triangle (g/mL) (g) (mL) (g) (mL) (cm 3 ) (g/mL) (g/cm 3 )

4. Density Problems The formula for density can be changed into three forms depending on the unknown: D = M/V V = M/D M = VxD 1. What is the density of a substance that has a volume of 50 mL and a mass of 135 grams? 2. What is the density of a substance that has a mass of 1572 grams and a volume of 200 mL? 3. If a substance has a mass of 273 g and a volume of 482 mL, will it float or sink in water?

5. Density Problems 4. If a substance has a density of.24 g/mL and a mass of 1250 grams, what volume will it occupy? 5. Bismuth phosphate has a density of 6.32 g/mL. What is the mass of 25.9 cm 3 of this substance? 6. The level of water in a graduated cylinder is 52.7 mL. After a solid object weighing 100.0 g is added, the level is 87.4 mL. What is the density of the object? 7. Mercury is a liquid at room temperature. The density of mercury is 13.6 g/mL. How many mL are there is 1.00 kg of mercury?

6. Density Problems 8. Pure ethyl alcohol has a density of.795 g/mL. What is the mass of 450 mL of ethyl alcohol? 9. A piece of metal with a mass of 147 g is placed in a 50 mL graduated cylinder. The water level rises from 20 mL to 41 mL. What is the density of the metal? 10. What is the volume of a sample that has a mass of 20 g and a density of 4 g/mL?

7. Finding the Density of an Irregular Solid To calculate density, you need to know both the mass and volume of an object. You can find the volume of an irregular solid by displacing water. 1.Find and record the mass of the irregular solid. 2.Add 15 mL of water to the graduated cylinder. 3.Measure and record the volume _________. Because the surface of the water in the cylinder is curved, make volume readings at eye level and at the lowest point on the curve. The curved surface is called a meniscus. 4.Carefully add the irregular solid to the graduated cylinder. Measure and record the new volume________. Analysis 1.Use the initial and final volume reading to calculate volume of the irregular solid________. 2.Use the calculated volume and the measured mass to find the density of the irregular solid________.