Last Thursday we revisited our slime recipes, looking for patterns of how different ratios affected the result.
Then we began a new topic, Energy, and a new curriculum… FOSS. This curriculum had really impressed me with its approach. It went well and the kids seemed to have a great time.
I sent home a book with a reading assignment. Read pages 5 to 9 — but it’s great if they read a little further.
Please be sure to send the textbook back to school this Thursday! We need it in class.
Last class we made slime. I gave them various ingredients and tools, but somehow there was no recipe! So their job was to work individually to experiment with creating and documenting their own recipe. They each did two or three trials, and got a wide variety of results. Some stickier, some stretchier, some harder… But a key goal was to document the recipe so that another slime-maker, uh, I mean scientist, could repeat the process.
For the first half of class today we learned about the difference between temperature and heat. We started with the question, if something is so hot that it will burn you, is it possible for the same material to have a higher temperature and not burn you?
We looked at exploding salt, the Leidenfrost effect, and the current Parker Solar Probe mission to study the sun. All these things are related and help explain why the answer to our question was in fact “yes”. It was cool to discover that the Parker Solar Probe flies through the solar corona which is a couple million degrees Fahrenheit without problem… while it is more in danger from the relatively-cool couple-thousand degree surface of the sun, despite being 13+ million miles away from the surface.
For the second half of class today, I presented the overall schedule for the science fair, and used an example project to show how they might proceed. I’m going to include that here even though it’s in kind of “note form”.
Science Fair Overview
Although we will be working on science fair in class some, I’ll need each parent to make sure that your student scientist’s project is progressing. The above dates are not hard and fast rules until January 10… But you don’t want to wait to the last minute!
Finally, it would be great if your students read pages 52-58. This will help me be able to complete the “Mixtures and Solutions” section of our book before winter break.
In today’s class we covered three things:
Usually I might give you more detail, but at the risk of revealing too much, this week we actually recorded the class because one student was out sick and wanted to attend.
That means you can view it to! This is an unlisted video, meaning it can’t be searched for in YouTube. But if you have an issue with it being available to people with a link, let me know as soon as possible.
Homework is for your students to refine their science fair projects. All projects are discussed in the video about midway through…
The question of whether or not matter can be cut in half indefinitely confounded early scientists. Last week’s homework secretly revealed one of the main ways this question was answered-however I assigned it so late, I decided we’d just do it in class.
Imagine a banana split is defined as 2 scoops of ice cream (Ic) and a banana (B). If you have 6 scoops of ice cream and four bananas, you can make three banana splits but you’ll have one banana left over.
Ic + Ic + Ic + Ic + Ic + Ic + B + B + B + B -> BIc2 + BIc2 + BIc2 + B
You could split that 4th banana into thirds and add the pieces to each bowl. But by our definition of a banana split, it would no longer be a banana split. If you continue this analogy to atoms and molecules, it means that if you mix 2 reactants, the two reactants will react in a particular ratio (in this case 2:1 for ice cream to bananas). If there is excess of one of the reactants, it will just be left over. The “limited reactant” in this case is ice cream. Get a 2 more scoops and you can make a 4th banana split.
Anyway, that’s a shortened version of what we talked about!
We also reviewed the fire triangle (Oxygen, fuel & heat), and did experiments with putting a spoon into different parts of a candle fire to see that based on where the spoon is placed, it will collect wax, soot, nothing, or water vapor based on how far along the combustion of the wax is. We also played with putting fires out. Here was a demo we did.
The homework is to read pages 42-51. It’s more science history, and makes for fun, quick reading. I read it aloud to my kiddos so we could have discussions.
This week we talked about rust and fire… Both chemical reactions that depend on oxygen — one very slow, one fast, both destructive. We learned about how burning hydrocarbons creates a lot of carbon dioxide, and how a fire extinguisher and other firefighting techniques attack the three corners of the fire triangle.
Homework was to read page 39 and 40, and to do the math problem on page 41. Since I am sending this out so late, I won’t expect that everyone will have done the homework. But if they looked at 41, there is a cool surprise coming. The very simple experiment described in that problem provided some of the first evidence early scientists had that there was such a thing as an atom! Namely, that when two reactants are mixed, there is a limiting reactant. That would not be expected if the limiting reactant could be further divided into mixed with the other reactant.
We played with magnetic tiles while reviewing homework to help cement the idea that chemical reactions involve reorganizing atoms. Next we explored the idea of how big an atom is, and how many atoms there might be in a grain of salt.
Then I told them I may have been making all this stuff up. How did they know? Where did all this information come from? We talked about the history of chemists and alchemists and how lots of experimentation led to models, and more complex models, and eventually the model of atoms and molecules.
We took some time to think about what a molecule looks like. Does it have color or shape? I asked them to try to forget the pictures they have seen so far and to imagine shrinking down to the scale of a molecule and draw what they see. It was interesting to see how differently they each approached this.
We finished off by looking at the results of a salt and vinegar crystallization project.
Homework this week was to read page 32 to 33, do the questions, and optionally make rock candy.
My blog entry for this week mysteriously disappeared, so I’ll be a little brief in my rewrite. We had an awesome observation and hypothesis-creation session to understand better the results of our crystallization project. I personally learned a lot in the process. Here you can see the students recording their observations in their lab book.
Next we explored the idea of conservation of mass by weighing baking soda, crystal citric acid and water before they reacted, and after they had reacted. We learned about atoms and molecules and how they reorganize during reactions, but do not disappear. Therefore we expected the mass not to change. I was unable to fool any of them when the mass did change because the reaction, in addition to yielding sodium citrate, also produces CO2 which escaped weighing. It also created brand-new water… Not the billion-year-old kind that we are normally so used to.
They all wrote down their homework, but just in case, please make sure students have read pages 28 to 31. They should also complete questions 1-4, which should take no more than 10 minutes.
Last week we did an experiment in which we made four solutions with varying concentrations of salt (1:1, 1:2, 1:3 & 1:4 salt to water ratio). We let them evaporate and took a look at the result in class today. 
Everyone agreed that the result in the 1:4 ratio was pretty cool. But why the cool crystals? Was it an anomaly? (New vocabulary word 🙂 ) The students immediately began hypothesizing that it must be connected to the different concentrations. But to be sure, we would need to do what scientists do — do another trial and see if the same thing happens. We started that, and also began thinking of theories that would explain what we saw.
In this 2nd trial, we added a few additional concentrations ranging from 1:1 to 1:6 to see if the pattern would continue that bigger crystals form in solutions with lower concentrations of salt.
It’s very satisfying to watch the group intuitively deriving the scientific process, rather than me having to do a boring lecture about the steps of a science fair project!
Homework this week is to read pages 16 to 19 (FOSS Gr 5) and look for clues that would explain the crystal formation we saw. It’s all there, but it might take a little support from a parent to make the connection. Please don’t just give them the answer, but help guide them. Here’s your cheat sheet:
A supersaturated solution tries to hold onto its dissolved material until that dissolved material finds something it can begin to crystallize around. As the numbers in the book show, the first 3 solutions have more salt than can be dissolved in water, and therefore there are hundreds of salt crystals on the bottom of the trays. As the water begins to evaporate, the salt in the water grows around these tiny salt crystals. You can see this in the leftmost three trays above. But in the rightmost three trays with a concentration of 1:4 or less, there are no salt crystals to seed crystal formation – so there’s nowhere for the salt to go. Eventually, the crystal must form — perhaps around a dust particle? — when most of the water is gone. When that first crystal forms, all the nearby salt frantically forms a big crystal on it. And that’s why we see a few big crystals.
After learning that the term “salt” refers to a more general chemical concept, we jumped into playing with oobleck — a cool combination of cornstarch and water that has very unusual properties.
Again, we tried to guess why this might be the case. We looked at oobleck under a microscope and saw how its shape and buoyancy could explain what was going on. We also looked at this image from a fancier microscope to get a better view.
At that point, everyone was a mess… Covered in oobleck. So we finished class playing with it outside!
Today we looked at another kind of mixtures called solutions. All the words related to solutions have parallel meanings. Solutions, solve, solvent, solvable, soluble, dissolve… We talked about the etymology of these words before diving into the day’s experiment.
Salt is opaque, water transparent. What happens when you mix the two? We talked about hypotheses, planning experimental processes, and conducting those experiments to test the hypotheses. Everyone wrote their hypotheses about what would happen in their lab book, and then we ran our first experiment to see.
In experiment 2, we hypothesized what the volume of a solution would be that was made of 100 mL of water and 100 mL of salt. Hypotheses ranged from 100 mL to 200 mL. What do you think would happen? Ask your child… Or try the experiment yourself! We extracted a small amount of the resulting solution which we placed in a petri dish. We then proceeded to dilute the solution with another hundred milliliters of water. The resulting volume may have been even more unexpected. We repeated the entire process two more times, in the process creating four petri dishes with solutions of various salinity. We are going to see if salinity affects evaporation rate. Here’s a sample lab book:
In addition to learning about solutions, the goal here is to also learn about making hypotheses, designing experiments, learning from our mistakes, and getting familiar with the scientific method in general in preparation for the science fair activities that will begin in earnest next month.
HOMEWORK for next week: Please read pages 12 & 13, and try to answer questions on page 14.
Of course, there was also some fun with solutions 🙂
problemsolvingmath 