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LecturePLUS Timberlake1 by Helen Hanson & John Macaluso An Introduction to Density.

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Presentation on theme: "LecturePLUS Timberlake1 by Helen Hanson & John Macaluso An Introduction to Density."— Presentation transcript:

1 lecturePLUS Timberlake1 by Helen Hanson & John Macaluso An Introduction to Density

2 lecturePLUS Timberlake2 Density Density is the ratio of the mass of an object to its volume D = mass = m volume V Units are g/cm 3 Note: 1 mL = 1 cm 3

3 lecturePLUS Timberlake3 Learning Check 1 Osmium is a very dense metal. What is its density in g/cm 3 if g of the metal occupies a volume of 2.22cm 3 ?

4 lecturePLUS Timberlake4 Solution Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass volume = g 2.22cm 3 = g/cm 3 = g/cm 3

5 lecturePLUS Timberlake5 Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 25 mL 33 mL

6 lecturePLUS Timberlake6 Learning Check 2 What is the density (g/cm 3 ) 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/ cm 3 2) 6 g/m 3 3) 252 g/cm 3 33 mL 25 mL

7 lecturePLUS Timberlake7 Solution 2) 6 g/cm 3 Volume (mL) of water displaced = 33 mL - 25 mL= 8 mL Volume of metal (cm 3 ) = 8 mL x 1 cm 3 = 8 cm 3 1 mL Density of metal = mass = 48 g = 6 g/cm 3 volume 8 cm 3

8 lecturePLUS Timberlake8 Methods for Finding Volume The density can also be found by calculating the volume of an object and measuring its mass. length width height V=(length)(width)(height)

9 lecturePLUS Timberlake9 Density of a Cylinder 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? r h

10 lecturePLUS Timberlake10 Density of a Cylinder V cylinder = лr 2 h = л x 5 x 5 x 10 (cm)(cm)(cm) = 250л cm 3 r = radius h = height D = 250/(250л) g/cm 3 D = m/V D =1/л g/cm 3 m = g D = g/cm 3 r h

11 lecturePLUS Timberlake11 Why Do Things Float? Things (whether solid, liquid or gas) with LESS density will float in a liquid with GREATER density. For example, this is why a stone (with HIGH density) will sink in water (LOW density), but a cork (LOW density) will float in water.

12 lecturePLUS Timberlake12 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) K K V W K W V V W

13 lecturePLUS Timberlake13 Solution (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) K V W

14 lecturePLUS Timberlake14 Density as Conversion Factors 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

15 lecturePLUS Timberlake15 Density Connections MassVolume kgL gmL (cm 3 ) mg

16 lecturePLUS Timberlake16 Learning Check The density of octane, a component of gasoline, is g/mL. What is the mass, in kg, of 875 mL of octane? 1) kg 2) 614 kg 3) 1.25 kg

17 lecturePLUS Timberlake17 Solution 1) kg Unit plan: mL g kg Equalities: 1 mL = g and 1 kg = 1000 g Setup: 875 mL x g x 1 kg = kg 1 mL 1000 g density metric factor

18 lecturePLUS Timberlake18 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) L 2) 1.25 L 3) 1.83 L

19 lecturePLUS Timberlake19 Solution 1) Unit Plan: g mL L 575 g x 1 mL x 1 L = L 1.05 g 1000 mL

20 lecturePLUS Timberlake20 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

21 lecturePLUS Timberlake21 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

22 lecturePLUS Timberlake22 Learning Check You have 3 metal samples. Which one will displace the greatest volume of water? g Al 2.70 g/mL 45 g of gold 19.3 g/mL 75 g of Lead 11.3 g/mL

23 lecturePLUS Timberlake23 Solution 1)25 g Al x 1 mL = 9.2 mL 2.70 g 25 g Al 2.70 g/mL


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