by Helen Hanson & John Macaluso
Density D = mass = m volume V Units are g/cm3 Note: 1 mL = 1 cm3
Learning Check 1 Osmium is a very dense metal. What is its a volume of 2.22cm3?
Solution Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass volume
Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 25 mL
Learning Check 2 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? 1) 0.2 g/ cm3 2) 6 g/m3 3) 252 g/cm3 33 mL 25 mL
Solution 2) 6 g/cm3 = 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 volume 8 cm3
Methods for Finding Volume The density can also be found by calculating the volume of an object and measuring its mass.
What is the density of a cylinder with a mass of 250.0g, a radius of 2.0 cm, and a height of 10.0 cm?
Density of a Cylinder Vcylinder = лr2h = л x 5 x 5 x 10 (cm)(cm)(cm) = 250л cm3 r = radius h = height D = 250/(250л) g/cm3 D = m/V D =1/л g/cm3 m = 250.0 g D = 0.318 g/cm3
Learning Check 3 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)
Solution (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1)
A substance has a density of 3.8 g/mL. Density = 3.8 g/mL Equality 3.8 g = 1 mL Conversion factors: 3.8 g and 1 mL 1 mL 3.8 g
Density Connections
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
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 factor factor
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
Solution 1) Unit Plan: g mL L 575 g x 1 mL x 1 L = 0.548 L 1.05 g 1000 mL
Learning Check A group of students collected 125 empty aluminum cans to take to the recycling center. If each can has a mass of 3g what volume of aluminum can be made if the cans were melted (Hint: d = 2.7 g/mL)? 1) 0.139L 2) 207 L 3) 4.85 L
Solution 1) 1.0 L 125 cans x 3g = 375g = mass 1 can So, V = mass = 375g = 139mL = 0.139L density 2.7 g/mL
Learning Check You have 3 metal samples. Which one will displace the greatest volume of water? 1 2 3
Solution 1) 25 g Al x 1 mL = 9.2 mL 2.70 g
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