Thursday, February 16, 2012

A different strand of chemistry

Yesterday, I extracted DNA from a strawberry. How often do you get to say that?

A parent of one student is a professor of biology at a local college and offered to come in and work with the class for 45 minutes. She started by giving a kid-friendly overview of what DNA is and how it works.
Then she got us garbed up in plastic aprons, gloves and goggles. Times like this I am reminded that as much as most eleven and twelve year olds push for autonomy from adults, they are still little children at hearts. Look how cute they are!

Once we got over how much fun it was to dress like a scientist, we got to work. We mashed the strawberries up and mixed them with a solution of soapy salt water. Vickie brought along lab tools to make this more authentic.
Then we strained the strawberry mash through filter paper and funneled it into a test tube.

Last we added alcohol to precipitate the DNA.

Most kids brought it home in a ziploc and left with their apron and gloves in their backpacks.

Lessons learned:
1) Personal lesson: I don't often get to be a student in a discipline I know so little about. Sure, I attend professional development for topics related to my teaching and personal writing. But I can't think of the last time I got to think hard about something so outside my areas of expertise. I enjoyed having a chance to be a student and will have to seek out other ways to experience this again from time to time.
2) Each of my students furthered their knowledge about DNA. For some this means now they've heard about DNA and know it's a part of who they are. For others this means they have deepened the knowledge they already had from other life experiences.
2) Science is fun! The tools are fun, the garb is fun, and if you keep working hard in school, it is a career choice.
Here I am modelling how it's ok to look like a total dork wearing lab gear.

How lucky I am to have parents willing to donate their time and work with my students!

Tuesday, February 14, 2012

Class Parties

As much as I enjoy eating healthy, local foods, I also love my junk food. If you don't believe me, ask my husband and he'll tell you about The Great Pop-Tart Debate of 1993. My position was that I didn't want too many pop-tarts around, because then I would eat them. Wouldn't you?

Because it's all about balance and finding ways to enjoy the unhealthy foods in moderation, simultaneously making sure to keep piling those fresh fruits and veggies onto your plate. I have often had class parties where there is a lovely balance of sweets, veggies and dip and fresh fruits. And most kids seem to take a balanced plate full of foods when given the opportunity.

The hardest part about having this kind of a party is that it falls on parents to send in the snacks. Times are tight and unfortunately, sending fresh produce in to school for a party is often more expensive than many families can manage. Which is why our holiday party in December was integrated with our U.S. Geography unit and we cooked our entire feast in the classroom.

Today I wanted to sponsor a class party again, but was also working with the lovely reality of a morning field trip to the Flynn Theater in Burlington. So whatever we made had to be a quick project.

Enter the smoothie. Toss fruit, yogurt and a splash of sweetener in a blender and you've got a quick, yummy, healthy treat.

Yesterday we made yogurt, which we also did in the fall. This time I heated the milk up at lunch time and did most of the mixing myself. At science time we reviewed the process for making yogurt and made the connection to chemistry: the bacteria in the yogurt starter consume sugars in the milk and create a chemical reaction. We briefly touched on the fact that yeast is also a living organism that creates chemical change in food products, in contrast to the baking powder that can quickly leaven baked products.

Today we used the yogurt, along with leftover milk, bananas, frozen berries, and leftover caramel sauce to make made-to-order smoothies. I called over two kids at a time to choose their ingredients while the rest of the class watched a Valentine's Day edition of Cupcake Wars. No one complained that we weren't eating piles upon piles of sugar, and most kids rated the smoothies 3 or 4 out of 5.

I sent them home with all the little candies that come with the pre-fab valentines (which I can't stand, but that's a different issue). Balance. A healthy snack at school and some sweets to take home at the end of the day. Mission accomplished.

Monday, February 13, 2012

Video on Leavening

I found these great 5 minutes videos on Hulu and showed one on leavening to my class today to review Friday's baking soda/baking power experiments. There are several others on topics ranging from fluids to fermentation to Teflon. There's even one title "blowtorch"!

Sunday, February 12, 2012

Alert The Media!

On Friday afternoon, my fifth and sixths graders were focused on science for an hour and a quarter.

Friday afternoon.
Ten to twelve year olds.

Focused on schoolwork for over an hour.

If you are a teacher and reading this, I hope you are sufficiently impressed. For me, this was amazing on an alert-the-media scale.

The funniest part is that the lesson was borne out of my laziness.

So far we haven't done any experiments that explore baking. The possibilities are broad: baking is a chemical process; certain ingredients will make a cake rise; leaving out key ingredients can yield varied results. I have wanted to address some of this, but frankly, trying to figure out how to design an experiment that could be completed in the time we have and that would produce something edible has escaped me.

After reading the other night about what the actual difference is between baking soda and baking powder (something I've never understood or bothered to look into), I went into the kitchen and started messing around with those two substances. Based on my results, I decided we wouldn't do any baking on Friday, but we would test these substances and try to learn more about them using scientific process.

The question I posed was: How are baking soda and baking powder different? We did a quick review of acids and bases and I reminded everyone that the fizzy lemonade produced a chemical reaction because and acid and base were mixed and released a gas as part of their reaction. I introduced the word neutral to define water's relationship to acids and bases. We also reviewed other signs of a chemical reaction (energy release in the form of sound, heat, or light; color change).

I showed everyone the materials we had and how they would test for reactions: I had lemon juice, water and egg whites (which I discovered, thanks to the wonders of Google, are a mild base). They would need to mix each of these liquids first with baking soda, then with baking powder. And for this experiment they would need to record a procedure either before they started or as they worked. Add in recording their own observations and recording a conclusion, and this is the most independent experiment the class has done so far.

I let kids choose their groups with the understanding that if they fooled around, they'd have to re-do the experiment at recess on Monday. Then groups of three and four went off to get organized while I set out all their materials.

Once they had hypotheses written and data tables set up, they were okayed to get their materials and start testing. Some groups recorded their planned procedure before starting; some wrote it out as they tested.

Overall I was amazed to see how well each group worked together and how thoughtful they were as they did their testing. Sometimes working with friends helps with focus, but at other times it can be a hindrance.

In case you are wondering, the baking soda only reacted when mixed with the lemon juice, but the baking powder reacted with all three liquids. As kids moved into writing their conclusions, I reminded them to look back at the question and use their data to answer the question. Most kids correctly identified that the baking powder reacted more than the baking soda. When pressed to guess why, everyone was stumped.

Time for my five minutes of science/kitchen content: The cool thing I found when Googling the two powders is that baking soda is a base, but baking powder is a mixture of a dried base and a dried acid. When it encounters any liquid, a chemical reaction ensues. Which is why whenever I bake a cake or muffins, baking powder is one of the ingredients. We talked about how you could get the desired reaction with baking soda and a mild acid like vinegar or lemon juice if you didn't have baking powder on hand. And I also made sure everyone thought about how the gas bubbles give a baked product that nice lift, evidenced by the little holes you can see when you break it apart. Do brownies need baking powder? Not if you like them fudgy like I do.

Certainly there's a lot more to the role of baking soda and baking powder in the kitchen, more than I am aware of and could explain to my class. Regardless, my students spent a long chunk of time independently using the scientific method to investigate two real-life and common ingredients and draw some conclusions about them.

On Friday afternoon.

Friday, February 10, 2012

Pizza Lunch

Every Friday is pizza day at my school. Here's what today's meal looked like:

Clockwise, from the pizza, we have:
  • pizza with mushrooms and red peppers
  • pesto pizza with bonus pesto on top
  • salad with greens, red pepper and carrot
  • orange wedges, kiwi slices and star fruit slices
  • kale chips
  • egg salad
Many of the items on my tray came from a table you visit and choose from after the main lunch window. Other available items I passed up were grapes and apple wedges. (I know, I took a chocolate milk instead of white. In its defense, it's skim milk and doesn't include any high fructose corn syrup).

I took this picture because last week I had the most fantastic pizza with roasted beets and goat cheese. I was full all afternoon and right up to dinner time. Even when I pack a healthy lunch from home, I am ready for a snack around 4:30. I thought about the anonymous teacher in Chicaco, Mrs. Q. who ate school lunch for all of 2010. Only in her case it was like a punishment, and she did it and blogged about the experience to bring attention to a problem in her community and many others across the country.

No problems here. Our kids have access to an amazing meal every day at noontime. Don't you want to come eat at lunch at my school?

Coming soon: the most amazing science lesson that kept everyone's attention for an hour and a quarter on a Friday afternoon.

Tuesday, February 7, 2012

Sometimes chemistry blows up in your face

Perhaps I am being a bit dramatic with the title of this post...

For each chemistry lesson, I have tried to include three components:
1. Chemistry content
2. Practice with the scientific method in general, and with one aspect of it in particular
3. Something edible to make the food aspect of this unit practical, and not just baking-soda-and-vinegar-bubbly. I don't like the idea of wasting food as we learn something about science.

Let's check my track record so far:
  • Our rock candy crystallized, but not on the sticks. It's still lurking on the shelf next to my sink.
  • After we finished straining the applesauce, no one wanted to touch, let alone, eat it.
  • Kids enjoyed eating frozen apple juice on a stick.
  • Homemade salad dressing was a hit.
  • Kids reacted (pun intended) as if fizzy lemonade was the coolest thing they'd ever seen and tasted.
  • We never got around to eating the wrapped up potatoes and apples that didn't oxidize. And the ones that did oxidize...
So far, I seem to be batting .500 on the experiment edibility charts. What's your guess about the caramel sauce we tried to make this afternoon?

The question was whether sugar, when heated on the stove, goes through a physical or chemical change. Kids were split when they wrote their hypotheses, with a couple saying both type of changes would take place. The scientific method focus for the day was writing a procedure. As I did this demo, kids took notes on what materials I used and what steps I took. I collected these and will assess them in the next day or two and get feedback to those who are not quite on track with this skill.

Here's what happens when you heat sugar: first it melts into a liquid (its melting point is over 300 degrees) - physical change. Then it starts to change color -- chemical change -- and you want to take it off the heat while it is a light, straw color. The longer it heats the more the sugars break down and if it gets too dark, it won't taste sweet at all. (An interesting side note is that this dark, used-to-be-sugar compound, can be used to darken stews and gravies.) Once off the heat, add water in a 1:1 ratio with the amount of sugar you heated. Do so carefully! The sugar liquid is hot and will spatter if you pour haphazardly. Now you heat the mixture to boiling, boil for several minutes, take off the heat, and serve as a caramel topping. It's not as rich as caramel sauce, which is usually mixed with butter and cream, but it has a warm, sweet taste and a maple syrup consistency.

I have to mention that I did this experiment three times at home in the past couple of days, tweaking the process. The first batch got way too dark and hardened into a solid black sheet in the pan, presumably un-sweet. The second batch was the right color but I boiled it too long and I burned the roof of my mouth trying to eat it before it hardened to glass. I wanted a topping that would pour after if cooled so I didn't end the school day sending half the class to the school nurse with first degree burns on their tongues and palates.

Of course my efforts at home only demonstrated to me what should happen! In the classroom, the sugar took forever to heat and melt for two reasons. The plug-in burner is tediously slow to warm up and I was trying to make a larger batch than I had made at home. More sugar means less heated surface area to make contact with in the pan.
It's not very interesting to watch your teacher stir a bunch of sugar in a pan for 10 minutes.

Finally the sugar melted but the liquid clumped to the unmelted bits and it started to change color before it was all liquid. I guess physical changes and chemical changes can happen simultaneously when there's that much sugar.

You can't holler, "Hey sugar crystals! Can you guys wait until everyone's melted before you engage in a chemical reaction?"

The lesson continued on in super slo mo compared to my practice trials.
When you add water to clumpy sugar, the clumps don't dissolve right away...

...but eventually they do, and then you just have to wait another eon for it to boil.

Kids finished their procedures, wrote observations, cut up apples, but also got silly and noisy. In the meanwhile I watched the clock tick along, knowing there was no way we'd make it to tech lab by our scheduled time. Thankfully, Frank in the tech lab is an uber-flexible guy about things like this.

The happy ending is that they all loved the caramel sauce. A dozen apples were devoured in no time and they walked to the tech lab, smiling and licking their fingers.

Sunday, February 5, 2012

Warning: this post has nothing to do with cooking

Chemistry is a real part of our lives.

When I wrote this unit I wanted to make chemistry relevant to my students. Years back my school developed a collaborative process for unit planning that, while it is not required, is an excellent tool for planning a unit with teaching specialists (art, technology, etc.). Oh, and also a trained facilitator facilitates the planning process. (Is there a good synonym for facilitator? I couldn't think of one.)

This chemistry unit was planned with the art and technology teacher. In addition to using cooking as a lens for examining physical and chemical changes, our class has also worked with Vera, our art specialist, to examine how physical and chemical changes apply to art materials.

So far we have analyzed the medium of watercolors and how they come in solid and solution form. We crushed up a bunch of old, cracked watercolors, dissolved them in water and left them to dry in small containers. Some students squeezed liquid watercolors out of tubes that we starting to harden and left those to dry, too. And -- I thought this was the best one -- a couple students poured liquid watercolors into small containers and used a hairdryer to evaporate the water and leave behind solid watercolor.

Last Thursday we went to the art room, mixed up a bunch of plaster, and made hand print casts, the kind I remember doing in our utility room with my father when I was about three. Almost everyone agreed that plaster mixing with water is a chemical change because once it hardens, you can't get back to plaster powder and water. Everyone but one student who is positive that you can smash it up into little bits and do the whole process over again. This may be his independent experiment...

At any rate, when you mix plaster and water, it also heats up, but not for quite a while. This heat energy is another indicator of a chemical reaction. Kids got to experience this warming of the plaster late in the game, but the focus was more about them being little kids and playing with the plaster. Which is charming, in a way.

Friday we brought the two medium together and kids painted their hand prints with the watercolors we liquifies and reconstituted. A perfect Friday afternoon activity! And aren't these kiddos cute?

Wednesday, February 1, 2012

Oxidization happens

Who knew that cutting open some apples and potatoes qualified as a science lesson?

On Tuesday, the question was: If you cut open fruits and vegetables, do they have a chemical reaction with the gasses in the air? It is so interesting to me that most students intuitively hypothesize correctly, even when they don't have the science knowledge to understand why.

In the spirit of gradually releasing responsibility to students, after they recorded hypotheses, they read over the procedure and planned how to collect data on their own. We did do a quick check in on the procedure, and students had a chance to ask questions about issues that weren't clear to them. How many times will we do observations on the cut up fruit was a biggie, and showed me they were doing good planning for their observation charts. One savvy students wanted to know what the control was: the wrapped or unwrapped fruit. Kids were thinking.

So we cut up the produce, wrapped half of it in plastic wrap, and everyone wrote down what the two sets of food looked like. The student photographer of the week snapped a bunch of pictures as everyone worked.

Later in the day we checked back and most kids clearly saw that the exposed items had browned but the wrapped ones had not. Some groups chose to unwrap the plastic wrap and also felt the surfaces of the potatoes and apples and noted the wrapped ones were moister. One group felt like they needed to collect more data and chose to leave everything out overnight. This morning they did a final round of observations.

Before anyone wrote their conclusions, I reminded them to look back at the question to make sure their conclusion addressed the question, and didn't just state what happened to the fruit. I collected these and looked them over after school – I will touch base with the kids who did not write appropriate conclusions as a way to guide them in the right direction moving forward.

Of course, I squeezed in a three minute science lecture: one of the gasses in the air is oxygen, it reacts with the fruit when it is cut open and the cells are damaged, it is called oxidization and other examples of oxidization include metal rusting. Applying lemon juice to cut up fruit is one way to inhibit oxidization. Vocab connection: oxygen/oxidization.

Tuesday afternoon also is the day we go to the school's tech lab. This unit was planned collaboratively with our technology guru, Frank. (Also with our art teacher, Vera. More on that another day.) Part of our work Tuesday was to look at projections of the pictures our student photographer had taken and discuss which pictures could be used in a lab report/presentation. Kids taking pictures makes for a mixed bag on the iPad; hopefully our exercise got them thinking about how important it is to plan ahead for getting a picture at the “right” time in an experiment and how to compose a decent picture. Clearly this is something I need to keep working on; I missed the opportunity to get a picture of the lemonade fizzing!

Which of the pictures above do you think we decided would have a place in a lab report?