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Summary
In this lab, students will learn how volume and mass affect density as they make comparisons and calculations.
Grade Level
Middle and Elementary School
Objectives
By the end of this lab, students should be able to
 Differentiate between density, mass and volume.
 Calculate the density of an object.
Chemistry Topics
This lab supports students’ understanding of
 Density
 Mass
 Volume
 Measurement
Time
Teacher Preparation: 10 minutes
Lesson: 4560 minutes
Materials
 3 bags of cotton balls in numbered Ziploc baggies of equal weight and size
 5 equal size heavy cardboard gift boxes that you will number
 Content suggestions for boxes: sand, cotton balls, paper clips, gravel, rice, pompom balls, cereal, feathers
 Scales
 Rulers
Teacher Notes
 Prepare three numbered Ziploc baggies of cotton balls of equal mass. Then, remove the air completely from one of the bags of cotton balls, remove approximately half of the air from the second bag, and the third bag should be completely full of air, like a balloon. Each bag will have successively smaller volumes. Be sure to tell them that each bag contains the same mass and number of cotton balls.
 Choose materials for the boxes and prefill each before the activity.
 Depending on the number of students, you may want to make multiple sets of the 3 bags of cottons balls, and the 5 boxes. Alternatively, you could have the class work together and share collected data.
 Optional: You may want to divide the class into five groups, and have each group complete one of the density calculations for the activity.
 This AACT Density animation may be a helpful followup to this lab activity.
For the Student
Background
Everyday people compare objects but some of the terms may lead to confusion. Often someone will say, “This is heavy” or “Wow, that’s a lot.” Are they talking about the mass, the volume or the density? During this activity, you will discover the difference between mass, volume and density and how to use these scientific terms.
Prelab Question
 How is mass measured? Give an example of a mass measurement.
 How is volume measured? Give an example of a volume measurement.
 What is the formula for density?
Problem
How does a change in volume or a change in mass affect density? Can we calculate and compare the density of several unknowns?
Materials
 Bags of cotton balls
 Boxes filled with unknown materials
 Ruler
 Scale
Procedure
Part 1:
 Compare three baggies of cotton balls. Lift each one and see which feels like it has the greatest mass? Record your predictions as “heaviest,” “medium,” or “lightest” in the data table below.
 Measure the mass of each baggy and record it in the data table below.
 In the data table record the volume occupied inside of each baggy as “largest,” “medium,” or “smallest.”
Part 2:
 Lift each of the five boxes. Which box feels the heaviest? Record your predictions in the first column of the data table.
 Using a ruler (cm) measure the boxes to determine volume (use the formula below). Formula: Volume = Length × Height × width
 Use the balance to determine the mass of each box and record in the data table.
 Using the formula for density, calculate the density of each box. Be sure to show your work in the calculation section provided.
Data
Part 1  
Baggy  Mass Prediction  Actual Mass  Volume 
1 



2 



3 



Part 2  
Box  Prediction  Volume  Mass  Density 
1 




2 




3 




4 




5 




Calculations
Use this section to show your work for the density calculations for each box:
Analysis
 How did the mass and volume of each of the baggies compare?
 Will the bags each have the same value for density? Explain.
 How do the volumes of each box compare?
 Was your prediction correct for identifying the heaviest box? Look inside the five boxes.
a. What was inside the box with the greatest density?
b. What was inside the box with the smallest density?  What makes something feel heavy? Is it mass, volume or density? Explain
 Ships float and anchors sink. Hot air balloons float up into the sky. Ice floats in a glass of water. Applying what you learned in this lab, why would ice (solid water!) float in liquid water?