Many teachers know the value of finding those surprising science experiments and demonstrations that hook kids’ attention.  One popular one is to have kids predict whether soda cans will sink or float, which turns out to be a nice hook for ideas of density.  Kids generally figure that if one thing of a kind sinks or floats, so will all the others.  So when the regular soda sinks, most will predict that all the other ones will sink too.  Much to their surprise, the diet soda generally floats.  Why?  Regular sodas are loaded with sugar, and that increases the density of the soda.  Diet sodas have aspartame, and a lot less of it per volume (take a look at the side of the can).  Steve Spangler’s site has a nice description of this activity.

I want to say more about the soda can activity (and why it is, in a way, a bit of a lie!) but first a few asides:

- This is, of course, also a great lesson in why sugared sodas are so bad for you.  That’s a lot of sugar.  Another astounding experiment I saw in this regards was to have kids weigh a piece of sugared gum, like Bazooka.  Then chew it, while the teacher talks about density and weight and stuff.  Then weigh the gum again.  It is surprisingly lighter.  Where’d all the weight go?  Look and see how many grams of sugar are in the gum.  That’s now in your belly.

- Kids have a lot of trouble with density.  They often think that “light” things float and “heavy” things sink.  Take a piece of soap and show that it sinks.  Break it in half and ask them to predict whether it will sink or float.  Many will predict that it will float, and will be visibly astounded when it still sinks.

- Another great density experiment is to take a piece of aluminum foil.  When it’s flat, it sinks.  When it’s crumpled up, it holds air, and floats.  More info here.

- Lastly, I’m forever enamored with the work of Dan Schwartz, who has kids invent the solution (for example, the formula for density) before telling it to them.  He calls these invention activities “Preparation for Future Learning” and there’s a lot of evidence to show that they’re effective.  For example, for density, he shows kids a bunch of cars with clowns in them and asks them to come up with a “crowded clown index.”  The index has to differentiate between, for example, the small cars with many clowns and the small cars with few clowns, as well as a large car with few clowns and a small car with few clowns.  Even if they don’t come up with the standard formula for density, students are ready to hear the expert solution, and also understand why density is a useful construct.  This goes along with the idea of giving a need for a vocabulary word before introducing the word itself.

OK, so now for why the soda can trick is (sort of) a lie.  It doesn’t always work.  It’s important to test the cans before you do this as a classroom activity (unless you want to turn it into an investigation of ‘why didn’t we see what we expected?’).  There is some variability in how sodas are canned, both within and across brands.  Is the advertised volume actually in the can?  (The only way to know is to open the can, though you can also weigh the can, as long as the same mass of aluminum is used).   Sometimes there might be extra air in the can, turning what should be a “sinker” into a “floater.”     Also, sometimes a bubble can get trapped under the can (so tip it sideways).   The temperature of the water also changes its density, so conceivably the temperature of the water could change the outcome of the experiment, though I’d be surprised if this was a large effect.

So, it’s a bit of a “lie” because you never know, perhaps you chose a floater and a sinker that float and sink because of different amounts of trapped air in the can, rather than because of density.  One could imagine turning it into an inquiry experiment, where students try to confirm the teacher’s hypothesis that the floating and sinking is due to density differences — a simple weight and volume determination of the soda in the can could do the trick, and would be a great experiment for students to suggest.  After all, don’t believe it just because teacher said so!

Image from Ngchikit under CC Share Alike (more info here).

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Looking for some activities to jazz up your class lecture on the cell and biology?  Here are a few hands-on teaching activities for middle school or high school:

Here are some cool cells to look at under a microscope:

• Cheek cells
• Onion cells
• Thin smears of ripe versus green banana, stained lightly with iodine.  Says Karen Kalumuck:  “You should see sickle-shaped structures that are amyloplastics – starch storage organelles.  You’ll see more of these in one of the types of bananas than the other, and can correlate with taste.  Predict which banana will have more darkly staining amyloplasts?  What happens to the starch?
• Compare tomato cells with pulp cells.  The skin cells are bricklike, providing structure, whereas the pulp cells are like balloons, to store starch with the lowest surface area to volume ratio.

No access to a microscope? Check out the Exploratorium’s Microscope Imaging Station — you can see videos of sea urchin cells dividing, stem cells, a zebrafish heart cell beating, and more. Any of the images here can be used in educational settings.

You can also build a cell model, and “scale up” cell and organelle dimensions to human scale.  If a cell was the size of my head, how big would a mitochrondria be?  Or, build a 3D diaorama inside a shoebox.  One teacher uses the analogy of a school — the nucleus is the principal’s office, the DNA is the school files, the teachers are the ribosomes, the students would be proteins, and the school bus is a vesicle.  Or, list a set of different analogies (the cell is like “The Simpsons”, the cell is like “a city”)  and let students choose, and make their set of analogical functions.

You can also model a cell membrane using soap film. You can stick a wet finger through a bubble film, just like plasma membranes are selectively permeable.   See this activity here.

This Traits of Life website at the Exploratorium has a set of online interactives and downloadable posters and articles.

You can do a play or drama about the cell — here’s an example about the Immune System from our teaching tips podcast.

Create a bingo or board game where students read off the functions of the parts of their cells, and then place those parts on the cell diagram.

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It seems to be in vogue to teach about climate change.  Thank god.  I mean, is there anything else more confusing nowadays?  Teaching students just to wade through the puddles of mud being slung across party lines is a message in media digestion in itself!

Luckily there are many resources being developed to help educators teach about climate change.  Here I’m listing a bunch that I’ve been running across.

1.  Free standards-based climate change films (polar regions)

From CIRES in Boulder comes a set of films for use in the classroom.  Sadly, they’re right now out of DVD’s, but you can see all the clips on their website. They say:  “The film contains 7 stand-alone segments appropriate for use in all kinds of science classrooms and informal settings from the middle level through college. The segments illustrate the problem of climate change and how scientists are working in Alaska and Greenland to understand it. Each segment is about 10 minutes long.  The video was developed to align strongly with the National Science Education Standards across all science subjects”

Segment 1: Introduction to Climate Change
Segment 2: Polar History
Segment 3: Studying Alaskan Permafrost
Segment 4: Ice Core Drilling
Segment 5: Studying Glaciers
Segment 6: Studying Sea Ice
Segment 7: Conclusion and Solutions

2.  Hot questions about climate change

Also here in Boulder (working for NCAR/UCAR), my fellow blogger Sharon Glassman has created a set of 30-second climate change videos, such as “What difference can a few degrees make?” (embedded below).  She says:  “The segs are fun, trustworthy, free – and designed to be spread through the atmosphere of the Web and friendship.”
©UCAR

3. Climate Discovery online courses

Also from the National Center for Atmospheric Research (NCAR) are a set of online courses. They are accepting registrations for winter term (starting Jan 22nd) here.   They cost $225 and there are several courses available.  They say:  “Are you seeking a K-12 professional development opportunity that will enhance your qualifications, competency, and self-confidence in integrating Earth system science, climate, and global change into your science classroom? The National Center for Atmospheric Research (NCAR) offers a series of six and seven week online courses for middle and high school teachers that combine geoscience content, information about current climate research, easy to implement hands-on activities, and group discussion. The courses run concurrently from January 22 through March 14, 2010.”

4.  How to effectively teach climate change

One teacher recommends a glacial melt activity here.  And a carbon calculator for kids.

CIRES has been working on a set of resources to help teach about controversial projects like climate change.   They have a set of helpful resources here. In particular:

• Common misconceptions about climate change (PDF)
• Climate change clicker quiz (PPT)
• Edutopia’s Taking the fear out of teaching global warming (HTML)
• Dealing with controversy (PDF)

5.  I also have a few activities and webcasts on climate change myself:

• Several hands-on activities about weather and climate here and here (such as a rice model of the composition of the earth’s atmosphere, and a model of how carbon dioxide resonates in the infrared).
• A set of webcasts – climate in the past (a synopsis of the included activities here) and in the future (a synopsis of content and activities here).

Also recommended are the following two books:

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I’ve got a new podcast posted, this one with my esteemed colleague Valerie Otero of the University of Colorado at Boulder.  She tells us why she thinks that the idea of student “misconceptions” is very dangerous — and gives us a new way to think about student ideas in the classroom, and some activities to address them.  This is in the Beyond Penguins and Polar Bears episode on Keeping Warm, and targets common student ideas about heat.  Still, the general message about misconceptions is, I think, one that every teacher should hear.

Listen to Warm Blankets and Cold Breezes (10 minutes)

You can also read this month’s content article on heat (what is it?  How do people and animals keep warm?) written by moi.

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A while back I blogged about a cool opportunity to get anything (yes, anything!) scanned on a Scanning Electron Microscope. Posted from the ASPEX website, here is a toy bunny, macrosize, and microsize:

Though how anyone could give up that cute wittle bunny is beyond me.

You can still send them samples (which I just think is so cool, and would be a great class activity), and they’ve just started a Name that Sample contest. The first correct answer wins a USB stick.  Here’s this week’s image:

They’ve already got a bunch of comments on there — go ahead, give it a shot!  This could be a good exercise in size and scale.  This is magnified 110X, and the whole thing is about 1000 micrometers across, or 1 millimeter.  So, the first guess on the site of “a blade of grass” is waaay off in order of magnitude (a blade of grass is probably about 10 mm).  Besides, it doesn’t even look like a blade of grass to me.  It also says that “Carbonaceous phases would be represented in darker tones where as Metallic features would be displayed in brighter tones.”  So perhaps this is metallic?  Lots of people have guessed that it’s some sort of adhesive being pulled apart.  But I’m not so sure that that “stretching” is actually dynamic.  SEM requires time to take, so whatever it is, it has to be sitting still while the image is being taken.  And the features are so regular…

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A tip of the apron to Elnore Grow for this one:

CHEMICAL APPLE PIE  (No apples but tastes like Apple Pie)
Yield 1 pie
Ingredients

• 1 recipe pastry for a 9 inch double crust pie ( I buy this already done)
• 2 cups water
• 1 1/2 cups white sugar
• 1 1/2 teaspoons cream of tartar (important as it gives it the acidic flavor)
• 25+ buttery round crackers (Ritz works well)
• 1/2 teaspoon ground cinnamon
• 2 tablespoons butter

Directions
1. Preheat oven to 350 degrees F.
2. Roll out pastry and set aside. Bring water to a boil in a large saucepan.
3. In a small bowl mix together sugar and cream of tartar. Add mixture to boiling water. Boil for a couple of minutes  (I actually do this at home and bring in a jar ready to pour over the crackers)
4.  Break up crackers into 1/4s or smaller and place in pie crust.  It should be pretty full.
5.  Pour sugar solution over the crackers and make sure all crackers get moist.
6.   Sprinkle crackers with cinnamon and dot with butter or margarine. Cover with top pastry. Seal edges and cut steam vents in top.
5. Bake in preheated oven for 30 minutes, until crust is golden brown. May need to cover top pastry partway through baking to prevent overbrowning.
The students are usually pretty doubtful about how it will taste.  I serve it with some ice cream or whipped cream and they love it and ask for more. Because one pie does not give each student (if you 25 or more) a very large piece, you may want to have extra pies done ahead of time. Sometimes I do this the last day of school instead of Thanksgiving.

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In optics experiments, you often need to create lines of light.  You can do this with light boxes, but they’re expensive, and tend to  have too many rays to be useful.  Laser light boxes are great, but again, spendy.

One teacher recommends using laser levels. These are the things made to help you hang pictures on a wall, so they’re level. Less than $20!  It’s made of a bright laser, with a cylindrical lens, which spreads the dot into a line.  You can see a demo here.

Zeke writes:

They create bright, dead straight, easy to use lines of light.  They do seem useful for Snell’s Law, but it isn’t always obvious how to do it. The most common way is to use a semi-circular dish. You might find that your biology teacher has absonded with them, too. Filled with plain Jello, the rays are really clear. You can’t see the protractor I photocopied and placed under the tray, but it works great. You can also fill them with other substances like water and corn syrup to demonstate different indexes of refraction. However, ray needs something to scatter it so you need to stir in some milk or other colloid. Another option is to get a fine grit sand paper and roughen the bottom of the dish. This will scatter the light through diffuse reflection.

I also like to use plastic bars. You might already have glass plates, but they are surely too thin. The ray of light made by the laser level is thick and if the object is too thin, the ray will go over the top making for a confused appearence.

I made the plastic bar by buying a thick hunk of clear plastic from the discard bin at TAP Plastic. I had them cut it into pieces. I bought six grits of sand paper and progressively sanded the bars until they were clear. The final bit required a liquid polish. The people at TAP explained how to do it to me.

It’s pretty cool and can show total internal reflection really great.

Here’s a video from Teacher Tube:

Have fun,

Many thanks to Marc “Zeke” Kossover for this information.

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I blogged a while back about mapping out the hot spots in your microwave with fax paper, or marshmallows or chocolate chips.  (Your food is not heated at the “nodes”, or cool spots, which is why we have those rotating plates).

Here is a decidedly un-yummy (but undeniably creative) take on that activity (as sent to my old teacher mentor):

I had a student read somewhere that you could use a cockroach to map out the hot spots. His home experiment (to my delight and of course horror) was to ink up the feet of several cockroaches and let them run around inside the microwave and produce a graph of x-y foot prints which mapped out the cold regions. It was working quite well he wrote in his experimental report – that was until his mother ascertained what he was doing. Gave him 8/10 for his report BUT took one mark off for not seeking an animal ethics and equipment approval from his mum.

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Ok, it probably wouldn’t be very yummy, but here’s another hands-on activity you can use that’s rather Halloween-like.  Called “Make a ‘mummy’”, this Exploratorium activity is a great way to demonstrate how mummification works, by drying out the tissue in a fish using baking soda.  Egyptians used a specific type of salt to do this, but baking soda will do the trick, giving you a tough leathery fish.

If you’d just left your fish out on a shelf, exposed to the air, bacteria and fungi would have begun to decay the fish, creating strong, unappetizing odors. Since all living things require water to survive, removing the water from the fish greatly inhibited the growth of these organisms, decreasing the unpleasant effects of rotting.

For an inquiry activity, try substituting salt for baking soda. Which one works best?  (Hint:  It’s not the salt).

Make him a little pyramid home. Imagine his little fishy afterlife.  Bury some fishy mummy friends for him to play with.

From Platonides on Flickr

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Extremepumpkins.com

With halloween fast approaching, it’s time to take advantage of a frivolous holiday to do some fun science stuff.

No post about Halloween would be complete without a reference to the Grossology site. Scroll down for  “lab activities”:  This gets high marks from one teacher who says, “It has the simpliest of the slimey things, glue slime, and fake blood.”

In that vein, read the post on “how to make slime” over at Schooner of Science.  The Schooner also has a recent post on zombies — an interesting story about the origin of zombies and a toxin-like powder which may, or may not, have put people into a zombie-like state.

The “whoosh bottle” is also somewhat spooky as a demonstration.  And you get to talk about gas laws  and combustion, too.

Fire is always fun.  If you google Exploding Pumpkin Experiment or Flaming Pumpkin Experiment, you can find some great things to do with those leftover jack-o-lanterns after Halloween.  Here is Steve Spangler’s version of an Exploding Pumpkin that carves itself.  Most people just have the pumpkin shoot flame from its mouth. You can get lycopodium powder (from Flinn Scientific, for example), and use a syringe to spray it along candles at the bottom of a pumpkin’s mouth, creating a fireball coming out of the mouth.  Obviously, t there are safety measures to consider.  The video below has the best explanation of how to do this that I found.

And here are a few suggestions from veteran teacher Raleigh McElmore:

Slime:  If you can score a magnetic stirring hot plate you can easily get Poly vinyl alcohol at a chemcial supply store and make up some great slime at 40 gr/L and mixing it with a bit of Sodium Borate (known as “Borax” and in many supermarkets detergent aisle) at 40 gr/L.

Your own grossology:  In elementary school I always filled a big pyrex bowl with peeled grapes that had been soaked in red food coloring. This brings out the “veins” in the grapes and I announced that “eyeball soup” would be shared with the students. A chunk of dry ice, the grapes and fill the bowl with cheap fruit punch gives you a seething and bubbling drink with “eyeballs” floating around.  Or you can, for realism, use sheep eyeballs. Give them to your star pupils. I’ll keep an eye out for you.

And to keep them on their toes:

A great magic trick that Penn and Teller invented is to bring two cans of sparkling soda (not anything else as this is messy). Give one can to a quiet student tell them to keep the can totally quiet. Give the other can to a hyperactive sort and tell them to “shake the can as hard as you can without touching anything”.  Did I mention that this should be done outside, oh yeah, do it outside.

Take the highly shaken can, put it in plain sight and say that this is the season for strange things. Tell the students that you will change fizz in the shaken can to the quiet can. Gently touch the quiet can and touch the shaken can. Mumble incantations about AYP and other scary things. Waste at least 30 seconds in mindless babble and then take the “quiet can” and hold it high while you open it. Curve your fingers behind it and squeeze the can as you pop the lid. It will shoot fizz all over everybody as you have secretly crushed the can. After you have sprayed everyone dramatically throw the can into a nearby garbage can to avoid students seeing the crushed can.

Then quietly open the shaken can. The gas will have gone back into solution by then and it won’t do anything. Explain to the students that teachers are given these powers, but only to be used for the good. Drink the calm can and draw attention from the garbage can with the crushed evidence.

Need more ideas?  Here are some links here and here and here.

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