Density of soap

When Kosrae campus asked me to come over for the summer to teach physical science, I knew I would be flying on a Beechcraft King Air with limited cargo capacity.

I realized I could not carry a large container of lab gear as I did in 2018. I knew that I could get some supplies on island, others I opted to have shipped in. The physical science course was designed to be delivered with minimal off-island supplies, this summer will test this principal to its core. The complication is that Pohnpei has more on-island options than Kosrae. And there would be no way to know which items would have to be ordered in and which would be on island beyond a few obvious givens.

One item that I knew I had to order in would be a digital weight scale that could handle a sizable range of masses. Soap would be an on-island purchase, but whether I could obtain rectangular slab soap was unknown. As was whether Ivory soap would be available. 

I was fortunate indeed that the materials I ordered all came in, intact, no missing or damaged shipments. The scale was an early order, that makes so many labs possible. Ace Office Supply on Kosrae had square slabs of Spa Naturals soap. The soap was priced above what the local market will bear. That meant the lab could proceed fairly easily (non-slab soap is harder to work with as one has to carve the curvaceous beauty bars into a slab before one can make measurements.

I got lucky when a day later at Michaela's store I stumbled into a serious supply of Ivory soap. Ivory is what gives this lab an element of surprise. 

Elise measures her soap

The yellow rulers were brought from Pohnpei, purchased at Ace Office there. I knew those might not be available here. I need that particular style for lab four. With only six of eleven students today, I had three groups of two. Two groups were given Ivory, I ran the demonstration on a Spa Naturals soap, which Elise is holding.

Elise massing her soap

I explained for the benefit of the pre-teacher prep majors that this lab could be done without a weight scale - but it might have to be modified to a single calculation. The mass in grams from the wrapper versus the measured volume. I did mention that one could theoretically cut the soap in half and hope that the half mass was accurate for the half chunk of soap. So there is a way to potentially do this density of soap laboratory including Desmos and a regression without a scale. 

Mary watches as CharlynRose measures the length of Ivory soap

I left the paring knives as a Kosrae purchase, only to discover that neither Ace Office nor Ace Hardware had paring knives. I wound up purchasing a rather random set of three kitchen knives from Ace Hardware. Hence the large size of the knife seen above.

Jeffan and Sue Malia look over their data

The cabinet in the science lab does have some supplies. To my surprise was this mass balance. Although costing significantly more than the one I ordered, the two measured identically to a tenth of a gram. The LCD panel on this unit is turning black, but the unit can still be read. I was pleasantly surprised to find that all of the materials I purchased four years ago and left on Kosrae were not only still in the cabinet, upon seeing them I realized there were in the same location and position I had left them in four years ago. The cabinet is like some kind of time capsule sealed in 2018. My intent this summer is to again leave materials behind. 

The Spa Naturals soap came in at a respectable 1.05 grams per cubic centimeter. Once again the computer laboratory was available, so I moved the class into the lab to show them the laboratory report layout. 

Ivory and Spa Naturals soap

Both of the Ivory groups obtained 0.93 grams per cubic centimeter. When I got to the part of the report where one reports on the discussion and conclusion, I noted that the Ivory data was probably errant data - everyone knows soap sinks. And all six students appeared to concur with this opinion. So I suggested that we needed to test the soap to verify that an error had been made. 

Kosrae campus is blessed with a physical science river. Complete with a physical science class pedestrian bridge. Have I mentioned how much I enjoy having a river as part of my classroom? Rainy weather provided a stream full of water.

The bridge is a tad slippery when wet. One has to be careful to only drop the soap in the water. 

The Spa Naturals was dropped first and, as expected and predicted, sank into the rocks on the bottom. Then the Ivory was tossed in. And plunged below the surface. And then popped up again, much to the surprise of the students.

Although blurry, the white soap chunk on the left side of the river is the Ivory soap headed for the Lelu lagoon. 

Barely visible, Ivory paddle to the sea heads on journey to the lagoon. 

Sina, Sue Malie, CharlynnRose, and Jeffan watch the soap head down the river. 

The rest of the lab period was spent providing one-on-one assistance to the students in getting their laboratory reports set up including performing the screen captures of the Desmos table, graph, and analysis. I also emphasized the need for a table caption. Monday June 6 is set aside for follow-up on this lab report - something I found necessary in summer 2018.