Arranging the Continents

Reader's Workshop


Writer's Workshop


Math


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News and Other Information

Lightships

At the end of our unit on sinking and floating, our lab is building lightships. We read the book Lightship, by Brian Floca to go along with this engineering challenge.

We have to make sure our lightships float, but also stay upright. We learned what happened to a boat that was too top-heavy - it sank!



When we started building our ships, we had to choose a material or a shape that would float and be stable, and we needed to include an anchor to keep it in one place. Here's what we came up with!

Can you make a floating island?

Are there any floating islands in the world? We wondered, so we tried to make some...


Can you make a floating island? from Stephen MacLellan on Vimeo.

Beans!

Yesterday, we read a book from Norah Dooley called Everybody Cooks Rice. In this book, the main character goes around her neighborhood looking for her brother for dinner. Each neighbor she goes to is cooking a different kind of rice, from Indian biryani to Haitian red beans and rice.

In our class, we started talking about beans, and the kinds of beans that we eat at home (and if we don't like beans, too). We decided we should make a class cookbook with different recipes that involve beans. We sent home an optional homework assignment to collect some recipes.

If your family has a favorite recipe with beans, send it in, and we will put it in our cookbook!

Here is a video Mr. MacLellan made about how to cook dried beans from scratch:


Dried beans take a long, long, long time to cook! Your recipe doesn't have to start from dried beans, canned ones are fine! We look forward to getting your recipes!

First Snow

Bar models!

This past week, we have been working with bar models to help us think about addition and subtraction problems. Bar models aren't a method of doing addition or subtraction. We will still be using the methods for addition and subtraction - using place value drawings and number-based strategies - that we learned in the fall. Instead, bar models are a great way to think about how story problems work using the beginnings of algebraic thinking.

These pictures show the product of a game we will play to introduce the concept of bar models. Students pull two cards out of a deck, then use two colors of cubes to show the two quantities. Then, they draw a bar model to show the additive process, with an addition and a subtraction sentence that match. The game is also a thinly-veiled excuse to practice basic math facts, and to explore the reciprocal nature of addition and subtraction.

Bar models can model addition problems, which we call "part, part, whole" problems, or subtraction problems, "whole, part, part". If you know both parts and you are trying to determine an unknown whole, it is an addition problem. If you know the whole and one of the parts, then it can be solved with subtraction. The model above can show both of these story problems. Can you figure out which is "part, part, whole" and which is "whole, part, part"? (they are a little sneaky, so read carefully!)

Kate went shopping with her robot two days last week. On Monday, she bought 7 cans of oil. She bought some more on Thursday. At the end of the week, she had 23 cans of oil. How much did she buy on Thursday?

Pete picked 7 pumpkins in the school garden. Maya picked 16 more pumpkins than Pete did. How many pumpkins did Maya pick?

You can do the same thing with larger numbers:

Alex ate 437 pizza slices on Monday. He ate 516 cucumber slices on Tuesday. How many slices of food did he eat on those two days?

Since with this story problem we know both parts, and the whole is unknown, we draw a bar model with the whole as the unknown, shown with a question mark, like this:

If it was a "whole, part, part" story problem instead, the question mark would go in the box of the unknown part instead of under the bracket.

When students get older, bar models can be a visual representation of an algebraic equation, with letters representing the unknown parts or wholes. Students will also use bar models for problems that require multiple steps to solve, as well as problems with more than two "parts" that make up the "whole". Bar models are a very useful tool, and a crucial part of the Math in Focus curriculum.

Raisins

We started experimenting with raisins way back in October.

First, we made predictions about what would happen when we put them into bubbly water. Then, we tested to see if our predictions were accurate or not. We found that the bubbles stuck to the raisins, and that some of the raisins would dance up to the top of the water, then fall back down. Here's what the testing looked like:

Our next experiment was a control test. We put the same number of raisins (from the same raisin brand) to the same plastic cups with the same quantity of water in them. Everything was the same as the first test, except that we used plain tap water instead of bubbly water. With plain water, the raisins just stayed on the bottom. Many raisins did have a couple of bubbles on them, but not nearly as many.

Then, many of the scientists in our lab wondered what would happen if we did other things with the raisins. Someone wondered what would happen if we squished one after it sat in the water overnight. Dr. MacLellan hit it with a hammer and bits of it went everywhere! That didn't happen with an ordinary raisin.

Other colleagues wondered what would happen if we put the raisins in other kinds of liquids. So, we put them in vinegar, cooking oil, soda, extremely salty water, and hydrogen peroxide. Then, we left them on the windowsill to look at again in two weeks.

Pretty quickly, the raisins in plain water grew mold, so we threw them out. I didn't put a picture of that here, because it's pretty disgusting. The other liquids were mold-free, so there must be something about each of them that kept the mold from growing. Besides mold, in most of the other liquids, the raisins had swelled up and were floating on top of the liquid. Only the raisins in the oil were still dark, shriveled, and resting on the bottom of the cup.

Vinegar:

Soda:

Extremely salty water:
These ones had a layer of salt crystals growing across the top of the water, as well as square salt crystals on the raisins themselves.

Hydrogen peroxide:
These were lighter in color than the others.

Cooking oil:
These raisins didn't change at all, and none of the liquid had evaporated.

Bubbly water:

After about six weeks of sitting on the windowsill, most of the liquids had evaporated.The salty water was very interesting:

The cooking oil was still the same:

And the hydrogen peroxide was all gone, but the raisins were bleached white!

With the soda and the bubbly water, they eventually grew mold, but it took a while. None of the others had any mold on them.

This was a fun experiment!