1. Define Density and explain how it is calculated.
2. Calculate one variable in Density = mass / volume (D = m/v) when given the other two variables.
A neat example of density changes is a lava lamp -- it's not very expensive and it's a dynamic example of the concept. (I used to have one in my classroom, but... it got stolen-- so store your stuff away!)
Here's a video discussing the concept and showing a few problems. (there is a small inconsistency in Problem #1)
For your information, from D = m / v:
v x D = (m / v) x v --> v x D = m
(v x D) / D = m / D --> V = m / D
I point out to my students that all three formulas are in "D = m/v" , it just needs to be rearranged algebraically.
Here is another video showing Density examples using a Factor-Label approach:
Here are some worksheets for your class:
The following worksheet might print out a little faded, but I like the variety of questions:
During this beginning month of Chemistry class, many Density labs can be performed safely -- this gives time to learn about chemical and fire safety and get lab safety contracts signed.
Here is a quick review of reading a graduated cylinder:
Once objects are collected for these labs, you could use them the next year. Check in your Science Department to see if there's already a collection of objects used for Density labs.
The 2nd method in the lab is for irregularly-shaped objects -- the method of Water Displacement is to be demonstrated by the teacher. This video provides a reminder of this technique -- it's not concerned about Significant Figures -- you can measure to one decimal place with the graduate cylinder used:
A graph of the data collected is required in the data analysis. If you want to graph by hand, here is a link to blank graph papers for your use:
I recommend drawing the points and line for one liquid before moving to the next liquid. Use a symbol around the points to differentiate the lines for the three substances (for example, circle, square, triangle). Include a Key on the graph to identify the line symbols.
Here's an online graphing program:
And a sample version of Graphical Analysis is available:
Check in your Science and Math Departments to see if your school owns a graphing program.
One more simple lab dealing with Density and the importance of Significant Figures is "Thickness of Aluminum Foil" . It's interesting to collect the class results, maybe on the board. With those values, you can discuss the consistency of the results.
My lab book "Chemistry on a Budget" is available for $20 at amazon.com or $23 at lulu.com:
The book contains 13 labs that require consumable materials you can purchase at local stores.
Each lab is presented with two possible report formats -- both labs use the same procedure but each has a different conclusion -- one with 10 questions to be answered as a conclusion, the other with a full laboratory report required. This gives the teacher the option of what type of report is desired. Each version is designed to be just two pages. This way the teacher can photocopy just one 2-sided page per student (saves paper).
I hope your school year is going well! Write me to let me know about your triumphs, challenges and questions!
Have a great weekend!