Chapter 5.8 Density Mrs. Baldessari Chemistry Objective: You will define and calculate density with appropriate units. 1 Density Take a look at the two boxes below. Each box has the same volume. If each ball has the same mass, which box would weigh more? Why? 2 Density Answer: The box that has more balls has more mass per unit of volume. This property of matter is called density. The density of a material helps to distinguish it from other materials. Density d = mass/volume (g/ml) 3 Density Calculate the density of each block. Block I Block II Mass = 79.43 grams Mass = 25.41 grams Volume=29.8 ml Volume = 29.8 ml 4 Density Block I – Density = 79.43 grams / 29.8 ml = 2.67 g/ml Block II – Density = 25.41 grams / 29.8 ml = 0.853 g/ml 5 Density units Density compares the mass of an object to its volume D = mass = g or g 3 volume mL cm Note: 1 mL = 1 cm3 6 Density Density is a physical characteristic of a material and allows us to determine what each block is made of. All pieces of matter made of the same material will have the same density. Different matter will have different densities. 7 Example #1 A certain mineral has a mass of 17.8 g and a volume of 2.35 cm3. What is the density of this mineral? mass Density = volume 17.8 g Density = 2.35 cm3 Density = 7.57 g/cm3 9 Example #2 •What is the mass of a 49.6 mL sample of a liquid, which has a density of 0.85 g/mL? •Cover the variable that your are mass Densitysolving = for volume x •Perform the math operation as it is 0.85 g/mL = shown in the triangle 49.6 mL mass = x = 42 g m m=(D)(V) D v 10 Concept Check Copper has a density of 8.96 g/cm3. If 75.0 g of copper is added to 50.0 mL of water in a graduated cylinder, to what volume reading will the water level in the cylinder rise? a) 8.4 mL b) 41.6 mL c) 58.4 mL d) 83.7 mL 11 Having trouble with the math? • Cover the variable that your are solving for m •Perform the math operation as it is shown in the triangle d v 12 Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL 13 Learning Check What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 3 3 3 1) 0.2 g/ cm 2) 6 g/m 3) 252 g/cm 33 mL 25 mL 14 Solution 2) 6 g/cm3 Volume (mL) of water displaced = 33 mL - 25 mL = 8 mL Volume of metal (cm3) = 8 mL x 1 cm3 = 8 cm3 1 mL Density of metal = mass = 48 g = 6 g/cm3 15 volume 8 cm3 Learning Check Which diagram represents the liquid layers in the cylinder? (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) 2) 3) V W K K V W K V W 16 Solution (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) V W K 17 Density Connections Mass Volume kg L g mL (cm3) mg 18 Learning Check The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass, in kg, of 875 mL of octane? 1) 0.614 kg 2) 614 kg 3) 1.25 kg 19 Solution 1) 0.614 kg Unit plan: mL g kg Equalities: 1 mL = 0.702 g and 1 kg = 1000 g Setup: 875 mL x 0.702 g x 1 kg = 0.614 kg 1 mL 1000 g density metric factor factor 20 Learning Check If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are given? 1) 0.548 L 2) 1.25 L 3) 1.83 L 21 Solution 1) Unit Plan: g mL L 575 g x 1 mL x 1 L = 0.548 L 1.05 g 1000 mL 22 Learning Check 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/cm3) are obtained from the cans? Note, 1 mL = 1 cm3 1) 1.0 L 2) 2.0 L 3) 4.0 L 23 Solution 1) 1.0 L 125 cans x 1.0 lb x 454 g x 1 cm3 21 cans 1 lb 2.70 g x 1 mL x 1 L = 1.0 L 1 cm3 1000 mL 24 Learning Check You have 3 metal samples. Which one will displace the greatest volume of water? 1 2 3 25 g Al 45 g of gold 75 g of Lead 2.70 g/mL 19.3 g/mL 11.3 g/mL 25 Discuss your choice with another student. Solution 1) 25 g Al x 1 mL = 9.2 mL 2.70 g 25 g Al 2.70 g/mL 26 .