Baking soda reactions never get old

There's nothing like a baking soda volcano. What kid doesn't love to see all that weird white foam come burbling out of a paper mache cone?

What's that you say? Volcanoes spew lava and hot ash, and not the product of a baking soda/vinegar reaction? No one pours anything into a volcano to make it erupt?

I love that today's experiment captured the natural student excitement about the baking soda volcano but also taught them some accurate chemistry.

We started by reviewing what a physical change is, emphasizing that phase changes and mixtures such as solutions and suspensions are reversible. Then we talked for a bit about what kids thought a chemical change would entail. I introduced the definition, which I now have posted on our display along with other new words introduced in the past couple of weeks. Then we were ready for the experiment.

Students wrote hypotheses to respond to the question: Does baking soda react chemically with lemonade. Most kids instinctively said yes, but their reasoning was all over the place. This is understandable; so far we have only dipped our toes in the vast field of chemistry. Next we reviewed the procedure. Last week when we strained applesauce I was underwhelmed at how poorly the small groups followed directions when they strained the sauce through the coffee filter. I wanted to make sure that this time they understood expectations and successfully completed the procedure. I also gave them time to plan how to collect data without giving any directions. At the end of the lesson I collected and quickly assessed their work to make sure everyone knows how to plan for data collection. We are moving closer and closer to the point where they will plan and execute their own experiments, so it is my job to make sure they are able to do each step of the process.

Small groups stirred baking soda into water and watched it dissolve. Good review of solution making, and also our control for this experiment. And then the joy and wonder! Baking soda fizzing in lemonade! Could science be any cooler?

Kids recorded data, wrote brief conclusions and many also jotted down new questions they have. One area we need to keep working on is making sure that their conclusions respond directly to the question being tested. We reviewed their conclusions, and then I gave the five minute science teacher lecture about why the baking soda caused a chemical reaction. Later, when I read over their questions, I was pleased to see that many of the questions they had right after the experiment were wonderings about why the baking soda reacted, or what was in the lemonade that made it react. Exactly the point I wanted to raise for them, and hopefully my science talked cleared things up. (They did a great job with data collection, too. Most kids made simple charts, but one student created a Venn diagram and another did labeled sketches for each mixture.)

Last and most fun part of this lesson: I had poured glasses of lemonade for everyone and said they could choose to drink it plain or try it fizzy. Every single one of them wanted to try it with the baking soda mixed in, and they all loved it! Kids, you can try this at home! One student started asking me if there was baking soda in carbonated soda, another wanted to put more baking soda in a partially-drunk glass of fizzed lemonade to see if it would create another reaction. They are thinking like scientists...

My regrets that it all happened so quickly, I never got the camera out. Hopefully you were using your imagination as you read this, If not, feel free to go into your kitchen and stir about 1/4 tsp baking soda into a tall glass of lemonade and see for yourself the magic of what happens.

Salad Dressing

You are probably aware that oil and vinegar do not mix, but did you ever consider it that when you shake them together you are creating a liquid-on-liquid suspension?

When I first considered this lesson, I thought perhaps it was a little weak on the cooking front. (Although not as weak as the rock candy. Those wooden stirrers still don't have enough candy to eat on them.) Then I wondered if my students knew what salad dressing was made out of and decided this might be a real learning experience for them. When I introduced the lesson I was surprised that even the most food savvy of my students didn't know that oil and vinegar were the basis of many salad dressings.

We started with some vinegar in small jars, and talked about how some pairs of liquids can be mixed together, but others create a suspension and ultimately separate. Then I measured oil into each jar of vinegar and sent small groups off to shake it up and time how long it took to separate. Although I told them to give the jars 10 shakes, there was some variability from table to table as the oil and vinegar separated. Whether this was from number of shakes or vigorousness of shakes is not clear; either way kids' interest was not captured by this activity. Plus it was Friday afternoon. I decided to cut my losses and leave it at the idea that they were forming a suspension and it was the basis for a vinaigrette.

I passed out small cups full of measured seasonings, kids shook it into their jars, and voila! Salad dressing!
Add some veggies from the kitchen*, and kids were munching on a healthy end-of-the-week snack with a homemade topping.

We put the extra in our class fridge and will use it next week with the leftover veggies and the school-provided snacks that come out of the kitchen every morning.

I consider this mission accomplished. Although we did not practice the steps of the scientific method, kids did experience both a science concept and gain practical kitchen knowledge.

*When I asked Emily if we could get some leftover vegetables for this lesson, she offered a crudite platter! How lucky we are to have a kitchen manager who used to run an upscale restaurant in the area.

Maybe I'm looking on the bright side of things, but I like how it's working out that we keep running out of time and have to finish up an experiment the next day. I think it's a helpful way to reinforce learning for many students, so I'll just pretend I planned for it to happen that way.

Thursday morning we revisited the applesauce experiment. Many kids had written conclusions that didn't show a deep consideration of the data collected, so together we talked through the idea that in a known solution (sugar water) no particles were captured at any level of straining. If applesauce particles were captured, then it must not be a solution. This kind of logical reasoning is not natural for all students, and I'm glad we took the time to review what we had observed. I introduced the concept of suspensions and then kids shared their questions.

I have been VERY pleased at the types of questions they have been coming up with. Having taught third and fourth grade for the past five years, it is inspiring to see how in this arena, their questions show the growth in thinking you'd expect between the two age groups. Also, as I've said before, the more good questions we collect, the easier it will be for students to select one and design an independent experiment in a few weeks.

Next I posed a new question: do solutions freeze at the same rate as a pure substance?

Writing a hypothesis is serious work.

Working together we created a series of four apple juice dilutions -- from 1/2 juice and water to 1/16 juice and the rest water. We also set up a cup of straight apple juice and straight water. Then we poured the rest of the juice into 16 cups and stuck sticks in them for an afternoon snack.

I love this picture, taken by a student. The colors really show the juice dilutions.

In the afternoon during math, Su put the tray of juice cups in the freezer. They had been chilling for an hour or so, so that they were all the same temperature when they went into the freezer. Then we had a wacky afternoon where we went trucking down to the kitchen at half hour intervals, each time walking through the gym where classes were going on. ("Walk on the red line; do not interrupt the game the kids are playing.") Each time I pulled the tray of juice cups out of the freezer, we'd look at each one and kids would record observations about their appearances. By the third visit, the pattern was clear: the straight water was the most frozen and the straight apple juice was still slushy. The juice pops weren't frozen so we had those at snack on Friday morning. Friday afternoon we revisited the data and concluded that pure substances freeze faster than solutions. Practically life application: salt on roadways in the winter create a salt/water solution that prevents the moisture on the roads from freezing up.

A big thank you to Emily in the gym and the ladies in the kitchen. I was less organized than I like to be this week, and hadn't warned any of them that we'd be trooping through the gym Thursday afternoon or descending on the kitchen as they were trying to finish their post-lunch clean up. I am constantly grateful for the flexible and kind people I work with.

Substituting applesauce for borscht

Do you have any idea how hard it is to find a jar of borscht in Vermont?

One of my student's questions last week was what other kinds of physical changes there are (besides what we have already learned about: phase changes and solutions). Apparently borscht is a good suspension to work with because you can strain it and see the various sized particles that are mixed into the liquid. Plus it'd be a great chance to introduce kids to a new food.

Only I couldn't find borscht at any of the local places we shop. So my husband stopped on the way home from work yesterday, walked the aisles of the large-ish grocery store with the manager, and came home empty handed. (Thanks for the effort, honey!)

What to do? Consulting my resource, other common supensions (think purees) include pea soup, tomato sauce, and applesauce. So I defrosted some of last fall's applesauce which is made up of nothing but apples and water, and as dinner heated in the oven I had science time in my kitchen! Applesauce passed the test and came to school with me today.

I posed the question: Is applesauce a solution of apples dissolved in water? Kids used a pre-made template to fill in their hypotheses without any discussion. This, after some deliberation on my part. Often my default is to give a lot of information as we start an investigation, but I purposely didn't this time in order to let the process of inquiry stand on its own. I was expecting many kids to overgeneralize what we have learned about solutions and say yes, applesauce is a solution because it's a liquid. But almost everyone commented on the pulp they've seen in applesauce and thought it was not a solution.

This morning in the shower, I had the a-hah realization that if we strained a sugar solution in the same manner as the applesauce, the sugar water would be the control and we would have something to compare the applesauce straining to. It sometimes concerns me that I am thinking about school in the shower, but I can't tell you how many good ideas have come out of those minutes under the hot water while my brain wakes up.

Next we read over the procedure I had embedded in their template and determined that a chart would be the best way to organize their observations. Then we worked through the steps as a whole group. We strained both liquids through a regular colander, a finer mesh strainer, and finally coffee filters, taking notes as we went.




The last step involved small groups straining the applesauce through the coffee filters. I was absolutely amazed last night to find an almost-clear liquid passing through the coffee filters, completely separate from the various-sized apple particles that are suspended in the sauce. The only problem was that the small groups got messy, squeezed applesauce all over the place, and generally didn't do anything that would allow them to collect useful data.

This group did a decent job of straining their applesauce through the filter.

I pulled everyone back together and we did the final straining over again as a whole group. Then we ended with everyone writing down their conclusions and any questions they now have.

Because our time was up and I had to end the day. So tomorrow we'll start science by sharing conclusions, and learning what a suspension is.

This is our question chart so far.

One thing I didn't like about this experiment is that much of the applesauce was not consumable by the time we finished with it. My hope all along has been that we will not "use" food to learn with and then dump it in the trash. But if you had seen the applesauce gummed up on the coffee filters, you would understand why we couldn't keep it. At least tomorrow our ice pops will get eaten when our experiment is done. Speaking of which, I have a test batch in the freezer. Time to go see how they are coming along...

Rock Candy wrap up

Have you been worried about the eight jars of sugar sludge hanging out in my classroom?

First off, there are only seven. In a move of typical clutziness, I knocked one over this morning. Sticky sugar clean up on aisle five!

The very happy news is that although my test run at home did not produce the desired results, the remaining batches at school are all slowly creating crystals of sugar. Very slowly. Like, I am wondering if I'll be able to clean it up before February vacation.

Today we finished the experiment part of the project. Although the recipe part isn't finished, we had collected enough data to bring some closure to the experiment. So we brought out the jars, made a final round of observations, and then looked back at the question: What will happen to a sugar solution if we heat the solution and leave it sitting for several days? The class hypothesis was that some of the water would evaporate and would leave behind sugar crystals we could see. This was, indeed, what happened. However we talked about how even when scientists disprove a hypothesis, they learn something new about the world and how it works.

As we talked through what had happened and why it had happened, lots of good questions came up. I captured these on a chart paper list started last week. Some of these questions may be fodder for student-designed experiments later in this unit. One student wondered if the crystals would grow better on string instead of the wooden stirrers we are using. Another wondered if room temperatures could affect crystal growth. (This after I showed them my sludge from home and they questions how hot/cold it is at my house, trying to reason out what had happened.) I am writing this from home but at some point I will post a photo of this chart paper list; I am always excited by the sorts of questions students articulate as a science unit of study is under way.

One point that came up in our observations is that it was hard to be sure that the water had actually evaporated. Duh! We should have either measured the height of water in the glass jars each day or better yet set up one container in a graduated cylinder or some other type of measuring cup so we could collect numerical data. It's a learning experience, right? Instead, we talked about the importance of a well-designed experiment. Hopefully I can model this better moving forward and students can learn from what I do as much as from what I overlook.

While our "recipes" in the next few weeks aren't as elaborate as they were for the US Geography unit, they will be more frequent. We will be straining applesauce tomorrow, freezing juice pops on Thursday and making salad dressing on Friday. Check back soon!

When Things Don't Go As Planned

Part One: When things don't go as planned...

This week we began a chemistry unit. The focus is on the differences between physical and chemical changes. It will be filled with what I hope is lots of fun lessons related to cooking and art materials. In addition to science content, students will practice using the steps of the scientific method and will design and conduct their own experiment as a final project.

My new bulletin board display, courtesy of the amazing Barb

We covered phase changes as one type of physical change yesterday, so today I introduced the concept of solutions. Using Vicki Cobb's book on kitchen science as my guide, I planned a lesson about sugar water solutions that is supposed to culminate in the creation of edible rock candy. Last night, I did a test run at home and things went smoothly, so I thought I was all set to go. Although most kids have a sense of where this project is heading, we set it up as a scientific experiment with me posing the question: What will happen if we dissolve sugar in water, heat it up, and then leave it for several days? Most students agreed with a hypothesis that the water would begin to evaporate and would leave some visible amount of sugar crystals behind.

Using Vicki Cobb's procedure, we dissolved sugar in water, heated the water and discovered that we could dissolve even more sugar in the water. Then we brought it to a boil and poured it into glasses and stuck craft sticks in the glasses, "just in case." We made observations about what the liquid looked like and left it for the afternoon. (I just realized, as I wrote this, that we didn't set up some sort of control glass of plain water, or unheated sugar water. Rats. I am a better cook than scientist.)



So mission accomplished. I left school thinking we'd check in on the glasses tomorrow morning and make more observations. Except for then I came home and discovered that the sugar solution I set up last night is a nasty slurry of sugary sludge, most of which is not clinging to the craft stick sitting in the middle of the glass.

This raises some questions:
1) Did I let the solution boil too long?
2) Would we have been better off using a piece of string instead of a craft stick?
and most importantly
3) Am I going to let my students eat this nasty sugar slime if it doesn't turn into the acceptable rocky candy form of sugar?

Here's what I have decided regarding questions numbers one and two. Who knows why this experiment didn't work? Either way, it will demonstrate that solutes can be recovered from solutions, showing that physical changes are reversible. And we got some good practice in with steps of the scientific method.

Question number three is a stumper. What do you think I should do with all the sugar sludge that may be forming in my classroom at this very moment?

To be continued...

Glory Nori!

When I first explained what a nori roll is to my class, reactions varied. Some kids have eaten it; one has even prepared it at home. But most couldn't understand why you'd want to wrap up anything in dried seaweed and then eat it. For the skeptical, it didn't help that the kids who have been already been initiated to the wonders of Japanese cuisine were salivating. I stressed that our cooking day would be a chance for everyone to see something new and make some choices about what they tasted: just the rice, a piece of the toasted seaweed, or maybe they'd go whole hog with wasabi in their soy sauce and pickled ginger on the side. Secretly, I imagined the entire class eating nori and raving about how cool it was.

We had just read a passage about California cuisine. It ended by saying that many diners first eat California rolls before trying more exotic Japanese dishes. For me this was certainly the case. Years back, I remember being very comfortable eating nori but thinking raw fish was NOT for me. Then I found myself at a Japanese restaurant with a friend. He tucked into a plate of sushi like nobody's business. Eventually I was offered one piece and tried it. From there I was hooked. California rolls may well be the gateway food to the love affair many of us have with sushi.

On the budgeting front, the good news is that I found sushi nori at a much better price at the second grocery store I checked, so I had enough for everyone to make a roll plus extra for sampling. When offered, most kids tried a small plain piece of it. Unfortunately, because a few didn't like the taste of that, they declined making or tasting a roll. Although the project went smoothly and many kids ate and tried something new, at first I was a bit surprised/disappointed. Several kids never even tasted one piece of nori. It's taken me a day of reflection on this food adventure to fully appreciate that this dish was way far out of some kids' comfort zone. One student almost seemed offended when asked to watch my demonstration of how to roll the nori.

In the end, about two thirds of the class made a roll and chose from carrot, cucumber, avocado and smoked salmon for their fillings.

I overheard one student talking to his friend say something along the lines of, “Dude, I've eaten this, but I've never made it before!”

Most kids ate and enjoyed it.

There was a lot of extra rice which I offered around to those who didn't want to try a roll, the selling point ended up being the offer of eating it with chopsticks.

Here I am, unhelpfully demonstrating how to use chopsticks.

"Hold them like this, then just pick up the nori."

One sixth grader eating rice tentatively tried soy sauce. When I asked her, she confirmed that she had never tasted that condiment before. (But she liked it; she used some today when the leftover rice was offered up at snack.) A couple students declined eating anything at all, but one of them chose to document the process from start to finish and took most of the pictures posted here. And I have to remind myself: everyone started off a different spot. Some kids discovered they really liked pickled ginger, others learned what soy sauce is. Even the ones that didn't eat anything were part of the experience. They saw something new. They heard about something new. They saw their friends eating and enjoying something new. Horizons were expanded.

And there's another way to look at it: The non-eaters saw their peers engaging in what seemed to them to be a risky behavior. Despite encouragement from those around them, they made a choice to avoid what felt dangerous to them. When I think of it that way, I have to be proud of those non-eaters. They didn't jump off what felt like a culinary cliff just because their friends did. Their middle school years are looming. Knowing how to say "No thank you" will be just as valuable a skill as being willing to try something new.

Grocery store musings

I'm standing in the grocery store muttering to myself about the cost of seaweed.

Translation: I'm holding the only brand of sushi nori at my local grocery store and am realizing that rolling nori with my students is going to be an expensive undertaking. I have already decided to bring from home rice vinegar, tamari and sesame seeds – the recipe uses so little of each of these. And I am donating the sushi rice – we have a ginormous bag of it at home that we are unlikely to finish in this lifetime unless we start rolling a lot, and I mean A LOT, more nori. I still have to buy cucumber and avocado. And would it be too much to include a small package of smoked salmon in this culinary adventure?

The problem with this yearlong project is I have no idea what is a reasonable amount to spend on each recipe. Between the Tari Shattuck grant money and money fundraised for class activities last year, I have about $250 to spend this year on ingredients. If push comes to shove I can also use some of my classroom budget money from the consumables line item. (Could we get any more consumable than food ingredients?) At some point I set a goal to try and keep recipes under $10 although in retrospect I am not sure where this number came from. Some recipes have been so inexpensive that it seems like I should be able to splurge on the occasional dish using specialty ingredients. But there's no road map here; I am just guessing and hoping that I'll have enough money to last me the year.

Clarity comes as I finish my shopping. One point of cooking with my students during this U.S. Geography unit is to help make connections between their stomachs and our vast country. To do that, I have to bring the world to them. Now that we've marched our way across the U.S. to the Pacific coast, it's going to cost a bit more to bring foods of the region back to them. We'll be making California Rolls on Thursday. I'm pretty sure it'll be worth the cost.