Set up hints – students prep items at their table then come up to the tank. After dunking, dry off with towels (I just drop it onto a thick folded up towel next to the tank). I have a bank of TBBs set up on the side of the classroom – students find the mass on their assigned TBBs then record results. Repeat trials. Towards the end of class, students enter all their data into the spreadsheet then I give them the volume of their film canister. Depending on the type of film canister, the volumes are about 39-41 mL. Confirm with a large graduated cylinder or water displacement tank.
This was the easiest, and most inexpensive way to make cartesian divers I have ever tried, and each student got to take theirs home after class. Did I mention how much fun it was?!
semi-transparent to transparent bendy straws – 1 per student
colored paper clips – 4-6 per student
scissors – 1 per 2-4 students
2L bottle with cap – 1 per 2 students
beaker of water – 1 per 2-4 students
tray to contain spills -1 per 2 students
optional: eye dropper with blue colored water
Part 1 – Demonstration:
As part of our density unit, we talk about the concept of buoyancy – why do objects float or sink? Using a 2L bottle of water, a glass medicine dropper, and some blue food coloring, we made guesses and observations about the cartesian diver.
The medicine dropper is filled with blue water, checked for buoyancy, and then added to a 2L bottle. Students gather to make observations. What do you think will happen when I squeeze the bottle? What will the blue water do? Why did it sink? Why did it float? What is happening to the air in the diver? What is the water doing? Did the mass of the diver change? The density? Students share their ideas and we come to a conclusion as to why the diver floats and sinks.
Part 2 – Build and Explore:
After the demonstrations, students get to build their own divers and explore on their own. Some tips to keep in mind:
Be careful bending the straw, any cracks will make the the straw useless.
After bending the straw, cut off the excess length of straw so that both side are equal in length. (You can save the rest of the straw for future activities)
Attach one paper clip as shown in the diagram below. Additional paper clips can be easily added or removed by sliding them on or off the main paper clip. (Like keys on a keychain)
Use a rescue hook for any divers that do not float back to the top.
Remind students to place the cap back on the bottle TIGHTLY – or water will shoot out of the bottle when they squeeze it.
Lunch or serving trays work nicely to contain spills.
This is a wonderful problem solving and hands-on activity to use as part of your density unit. The students enjoy the challenge and have a solid understanding of density after completing this activity. Even though students quickly figure out how to make the canister float and sink, making the canister suspend is pretty challenging and requires a lot of trial and error and problem solving.
To qualify as suspending, the film canister needs to float just under the surface of the water, with a small portion of the top just breaking through. How I also verify that it is suspending is by pushing the film canister to the bottom of the tank, if it comes up very slowly to the surface, it counts – if it comes up quickly or stays towards the bottom, it doesn’t count. Students then need to figure out that if it comes up too quickly, they need to add to the mass, if it comes up too slowly, they need to remove some of the mass. It will take several tries to get it just right.
one canister per 2 people works well, they can reuse the canisters if you don’t have enough to give each set of lab partners 3 canisters
if they reuse the canisters, be sure that they find the mass before they empty the contents
An assortment of small objects such as pennies, paper clips, stoppers, small pebbles, etc…
Introduce the Dunkin’ for Density Challenge – their goal is to make the film canister float, suspend, and sink by placing contents inside of the film canister.
Many students will say that the canister will float with nothing in it, but they must place a few objects in it for it to count 😉
On a side note, a mini history lesson on film and cameras is fun to discuss since most students have never used a camera that used film
Explain the procedures, review how to use the TBB, note that the film canister must seal completely and be air tight so that water doesn’t enter, and also demonstrate how to use the dunk tank properly and to dry off the canister before finding the mass.
Do not give the students the value for the volume of the film canisters until they have collected their data. If the students know the volume of the film canister, they may figure out the mass needed to make the film canister’s density close to 1.0 g/cm3.
The value is approximately 39 mL or 39 g/cm3 – verify with a large graduated cylinder that the film canister can fit inside of – or use an overflow can to find the volume (link).
I will give the volume to each set of lab partners individually and ask that they don’t share that information with the class.
Once students have calculated the density, collect class data on a spreadsheet projected on the board/screen.
Discuss results – why did the film canister float, suspend, or sink in the tank of water? What relationships did you notice?
For more lessons related to the Properties of Matter, click here (link)
Students will collaborate, problem solve, and persevere to accomplish each challenge
Materials – per group of 3-4 students
Task Cards – cut apart, laminate, and secure with a metal ring or brass brad
1 rubber band
4-6 pieces of string of equal length
This is one of the team building exercises I plan to use with my 6th graders during the first week of school. Many variations of this lesson can be found online. For this version, I created 6 different challenges for the students to tackle – each one increasing in difficulty. Not every group will get to complete all 6 challenges, and that is OK. The objective is to learn to work together as a team and not give up.
July 26, 2017 – One recommendation I have for this activity is placing the cups on the floor, when the cups fall off the table it makes it more difficult to complete the task in a timely manner.
Updated: Pictures September 2015
Discussion & Reflection
Which challenge was the easiest for you group to complete? The most difficult? Why?
Did your techniques change as you advanced to each challenge? Explain why or why not.
Describe a technique that worked best within your group.
Compare using two hands vs. one hand when holding the string to guide the cups. List advantages and disadvantages for each.
Compare using verbal and nonverbal communication, what were some of the challenges your group faced?
If you were to complete this activity again, what would your group do differently? What would you do the same?
Why are collaboration and communication skills important characteristics for scientists to have?
Did you feel like giving up at any point? How did you and your group deal with frustration?