Partnerships Implementing Engineering Education
Worcester Polytechnic Institute – Worcester Public Schools
Supported by: National Science Foundation
Measurements 6.F.3
Density and Hydrometers
Grade Level
Sessions
Seasonality
Instructional Mode(s)
Team Size
WPS Benchmarks
MA Frameworks
Key Words
6
1 – approximately 60 minutes
N/A
Class
Class
06.SC.PS.01
06.SC.PS.03
06.SC.PS.04
06.SC.PS.05
06.SC.TE.03
06.SC.TE.17
6-8.PS.1
6-8.PS.2
6-8.PS.3
6-8.TE.1.2
6-8.TE.1.3
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
Worcester Polytechnic Institute – Worcester Public Schools
Supported by: National Science Foundation
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
None
Essential Questions
1. What is density?
2. What is weight?
2
Partnerships Implementing Engineering Education
Worcester Polytechnic Institute – Worcester Public Schools
Supported by: National Science Foundation
3. What is mass?
4. What is a hydrometer?
Introduction / Motivation
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
Worcester Polytechnic Institute – Worcester Public Schools
Supported by: National Science Foundation
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
2
earth use 9.8 m/s , the gravitational force of the earth, when computing the
weight of an object. (Weight = Mass * Gravitational Force)
4
Partnerships Implementing Engineering Education
Worcester Polytechnic Institute – Worcester Public Schools
Supported by: National Science Foundation
Assessment / Evaluation of Students
Evaluate the worksheet completed by the students.
Lesson Extensions
None
Attachments
_____
1. Introduction to Density
2. What is a Hydrometer?
Troubleshooting Tips
None
Safety Issues
None
Additional Resources
None
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
Volume of Aquarium: _________ cm3
20 cm
100
The mass of 140000 cm3 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 measured depth of straw in mystery liquid
=
density water
density unknown
We know the density of water is 1.00 g/cm3. If you measure the two depths
of the pipets then you will only have one unknown variable (the unknown
density).