In this lab students will need to take accurate measurements of mass and volume for 14 different substances/materials in-order to identify what those substances are based on their density and other observed characteristics. Lab safety is a must even though the substances used are generally harmless. As students make observations we review how to deal with substances that are unknown. Some are liquid, some solid.
You will need access to scales that measure at a minimum accuracy of .5 grams but preferably to .1 grams. You will also need access to several household materials/substances (listed below) and containers that are all the same so when students are given an empty one they can take the mass and subtract that mass from their measurements of the liquids inside the containers. Label each container with masking tape and the letter you want it to represent. You should have students take the mass BEFORE determining volume as some will be left in the graduated cylinder when measuring volume. I also have a density set that has cubes of various materials that are all the same size. These density sets can be purchased through any science equipment supplier such as FREY, NASCO, FISCHER, etc. I take the cubes and put masking tape over the label of what the substance is as the purpose of this lab is for students to identify the substances themselves based on density and other observations they make.
The lab includes a pre-lab question section as students must prove they are ready to be able to take on this lab task prior to starting as this is one of the more difficult labs they would have done to this point.
Following the pre-lab there is a section of information on the common density of the materials that will be used in the lab for students to compare their measurements to. There is an emphasis on taking VERY accurate measurements and taking their time as well as using more than just density to help them provide evidence for what they believe each substance they are measuring is. They are require to write in complete sentences using scientific vocabulary.
The materials included in the density kit are:
Substances I use in addition:
Rubbing Alcohol 90% (it says 70% but the 90% is closer to the given density in the lab environment)
Hydrogen Peroxide (this is tough to determine compared to water for students)
Once the students are done taking all measurements and giving their justification they think each letter substance is I go through the list of what each letter really is. The students really can get into this part as they can't wait to find out how many they determined correctly. I sometimes give out suckers to teams who were able to determine all 14 with 100% accuracy.
Following the lab there are analysis questions for students to review/think about what they did and 2 additional challenge questions for teams to work on together.