Partnerships Implementing Engineering Education Measurements 6.F.3 Density and Hydrometers Grade Level 6 Sessions 1 approximately 60 minutes Seasonality N/A Instructional Mode(s) Class Team Size Class WPS Benchmarks 06.SC.PS.01 06.SC.PS.03 06.SC.PS.04 06.SC.PS.05 06.SC.TE.03 06.SC.TE.17 MA Frameworks 6-8.PS.1 6-8.PS.2 6-8.PS.3 6-8.TE.1.2 6-8.TE.1.3 Key Words Density, Hydrometer, Mass, Volume, Weight Summary The students will develop an understanding of the concepts of mass, weight, volume, and density and appropriate tools used to obtain these measurements. The students will calculate volume, weight, and build hydrometers to compare and measure the density of liquids. Learning Objectives 2002 Worcester Public Schools (WPS) Benchmarks for Grade 6 06.SC.PS.01 Differentiate between weight and mass, recognizing that weight is the amount of gravitational pull on an object. 06.SC.PS.03 Differentiate between volume and mass. 06.SC.PS.04 Define density 06.SC.PS.05 Recognize that the measurement of volume and mass requires the understanding of the sensitivity of measurement tools (e.g., rulers, graduated cylinders, cylinders, balances) and knowledge and appropriate use of significant digits. 06.SC.TE.03 Identify and explain the safe and proper use of measuring tools, hand tools, and machines (e.g., band saw, drill press, sanders, hammer, screwdriver, pliers, 1
Partnerships Implementing Engineering Education tape measure, screws, nails, and other mechanical fasteners) needed to construct a prototype of an engineering design. 06.SC.TE.17 Apply the metric system in design projects and experiments. Additional Learning Objectives 1. 6-8.PS.1 Differentiate between weight and mass, recognizing that weight is the amount of gravitational pull on an object. 2. 6-8.PS.2 Differentiate between volume and mass. Define density. 3. 6-8.PS.3 Recognize that the measurement of volume and mass requires understanding of the sensitivity of measurement tools (e.g., rulers, graduated cylinders, balances) and knowledge and appropriate use of significant digits. 4. 6-8.TE.1.2 Identify and explain appropriate measuring tools, hand tools, and power tools used to hold, lift, carry, fasten, and separate, and explain their safe and proper use. 5. 6-8.TE.1.3 Identify and explain the safe and proper use of measuring tools, hand tools, and machines (e.g., band saw, drill press, sanders, hammer, screwdriver, pliers, tape measure, screws, nails, and other mechanical fasteners) needs to construct a prototype of an engineering design. 6. Understand why properties of materials are important, and how they are used to decide what material should be used to create something. 7. Be able to explain the purpose of creating a prototype, and document its creation and purpose. 8. Students should be able to use materials available to create the most accurate prototype possible of the assigned task. Required Background Knowledge Essential Questions 1. What is density? 2. What is weight? 2
3. What is mass? 4. What is a hydrometer? Introduction / Motivation Partnerships Implementing Engineering Education Ask the students to tell you everything they know about mass, weight, volume, and density. Ask them if they know any tools that can be used to obtain these measurements. Procedure 1. Distribute to the students Introduction to Density worksheet. 2. Have the students examine the definitions and equations given on the second page of the worksheet. 3. Have the students use the equation of volume to obtain the volume of the fish tank on the first page of the Introduction to Density worksheet. 4. Next given the mass of the water on the Introduction to Density worksheet have the students compute the weight of the water in the fish tank. 5. Finally using the equation of density have the students compute the density of the water in the fish tank. For the following activity set up two graduated cylinders so that they can be seen by the students. Also you may substitute using detergent for any liquid that is thicker than water. 6. Distribute the What is a Hydrometer? worksheet to the students. 7. Explain the students that a hydrometer is an instrument used to compare the densities of two liquids. The farther into a liquid the hydrometer falls the less the density of the liquid. 8. Fill one of the graduated cylinder ¾ full with water and fill the other graduated cylinder ¾ full with dishwashing detergent. 9. Explain to the student that which ever pipet falls farther into the liquids, that liquid is less dense. 10. Place one pipet into the cylinder containing the water and one into the cylinder containing the detergent. 3
Partnerships Implementing Engineering Education 11. Show to the students the pipet in the detergent does not fall as far into the liquid as the water pipet and therefore the detergent is more dense than the water. 12. Measure the distance in centimeters that each of the pipets are submerged in the liquids. 13. Using the ratio on What is a Hydrometer? have the students calculate the density of the detergent. Materials List Materials per class Amount Location Copies of Introduction to Density 1 per student Lesson Copies of What is a Hydrometer? 1 per student Lesson Dishwashing detergent Enough to fill ¾ of the graduated cylinder House water Enough to fill ¾ of the graduated cylinder Sink Pipet 2 Kit Graduated Cylinder 2 Classroom Calculator 1/student Classroom Vocabulary with Definitions 1. Density The mass per unit volume of an object. (Density = Mass/Volume) 2. Hydrometer An instrument used to determine the density of liquids. 3. Mass The bulk of a solid object. 4. Volume The amount of space occupied by a three dimensional object. (Volume = Length * Width * Depth) 5. Weight - The amount of gravitational pull on an object. It is measured by multiplying the mass of an object and the gravitational force. For any object on earth use 9.8 m/s 2, the gravitational force of the earth, when computing the weight of an object. (Weight = Mass * Gravitational Force) 4
Assessment / Evaluation of Students Partnerships Implementing Engineering Education Evaluate the worksheet completed by the students. Lesson Extensions Attachments 1. Introduction to Density 2. What is a Hydrometer? Troubleshooting Tips Safety Issues Additional Resources Key Words Density, Hydrometer, Mass, Volume, Weight 5
Name: Date: Complete the following volume, weight, and density calculations using the equations on the following page. 1.) Maria is filling an aquarium for her fish Alvin. She needs to know how much water to put in the tank. The dimensions of the aquarium are 70 centimeters tall, 100 centimeters wide, and 20 centimeters deep. 70 cm 20 cm Volume of Aquarium: cm 3 100 The mass of 140000 cm 3 of special aquarium water: _142_ kg Calculate the weight of the aquarium water: Calculate the Density of the Aquarium Water: Name: Date:
What is a hydrometer? A hydrometer is a device used to compare the densities of liquids. http://www.fallbright.com/web4hydrometer.gif You can calculate the density of liquids by using the following equation: depth of straw in water density water = measured depth of straw in mystery liquid density unknown We know the density of water is 1.00 g/cm 3. If you measure the two depths of the pipets then you will only have one unknown variable (the unknown density).