Goldilocks & the Three Bears:

Goldilocks and the Three Bears is a well-known fairy tale and provides a great opening for scientific inquiry. 

Whatever version of Goldilocks and the Three Bears you prefer, you'll come to the spot when Goldilocks goes to eat the porridge.  She finds that Papa's porridge, in the largest bowl, is too hot; Mama's porridge, in the middle-sized bowl, is too cold; and the Baby's porridge, in the smallest bowl, is just right. 

Does this part of the story make sense, scientifically?  Would the largest vessel keep something the hottest?  What about the smallest vessel keeping it warmer than the medium-sized one? 

It's easy to test it out for yourself!

You'll need 3 jars/bottles/beakers, each a different size.  If I were at school, I would use three different sized beakers.  Because I'm working from home, I used three different sizes of Mason jars: a quart jar, a pint jar, and a half-pint jar.  You'll also need a thermometer.  I used a candy thermometer, because that's what I had at home. 

Fill each of the jars with hot water.  However hot you can get it to come out of the tap is fine, it's not necessary to heat it further. 

Take a temperature reading right away, so you know your starting point. 

For younger students:
Set a timer for 15 minutes and when it sounds, take a temperature reading for each jar.  If you wish, you take an additional reading after another 15 minutes.

For older students:
Have the students, working in lab groups, take and record the temperature of each jar of water at regular intervals (1, 2 or 3 minutes).  These students can then graph their data, which will show the rate at which heat is lost from each vessel. 


I started with water that was 125 degrees Fahrenheit.  After 15 minutes, I had the following data:
Papa (Quart jar): 115 degrees
Mama (Pint jar): 109 degrees
Baby (Half-pint jar): 100 degrees

After completing the activity, graphing and drawing conclusions, students can re-write the tale, incorporating what they learned from the lab.

Atoms: Is it full?

Fill a large, clear container with rocks/pebbles/marbles.  Ask your students, "Is it full?"  They will answer, "Yes," as no more pebbles can fit in.

Now pour sand in over the pebbles until the container can hold no more sand.  Ask your students, "Is it full?"

Finally pour water in over the sand and pebbles until the container can hold no more water.  Ask your students, "Is it full?"

At this point, you'll get some students convinced that it is full, but others will now be skeptical, based on what you've showed them so far. 

Ask those students, "What else would fit in this glass?"  You're working toward the idea of atoms being tiny particles, so small (some of them) that they could squeeze in between the molecules of water.  Once students have an idea of how small atoms are (sort of, it's awfully hard to truly understand how minuscule they are), you can proceed with your study of atoms. 

Refraction: Where’s the Test Tube?

I have been waiting nearly two years to share this with you, because I was hoping to find the appropriate lab-ware to borrow so I could photograph this VERY cool demonstration.  But, it hasn't happened yet and doesn't look like it will in the near future, so I've decided to share it with you, without any photographs.  I hope you'll try it.  If you do, maybe you'll take some pictures and be interested in sharing them!

Pyrex has the same index of refraction as corn oil. As such, this demonstration will only work with corn oil, not with any other kind of oil. 

Put some CORN oil in a beaker.

Place an empty test tube in the corn oil - it will appear bent due to refraction. Then, begin to fill the test tube with corn oil - the test tube will disappear! This could also be done with a small beaker.

If you have a mature audience, try this trick… place a broken test tube (be VERY careful, Pyrex is SHARP) into the beaker of oil (which already contains the hidden test tube), telling the students that it’s a restorative potion. Then pull out the whole, hidden test tube!

Moles: Challenge!

After discussing what a mole is (6.02x10^23 things), challenge students to bring in a mole of something.

Some examples to get you started...

A mole is...
...58 g of salt
...18 g of water


This is a good activity to do for Mole Day (celebrated October 23 - sorry to be late in sharing, you'll have to save it for next year!).

I would leave this as an extra credit opportunity for my students, as it's really beyond some of them. But, if you work with older or higher level students, go ahead and make them all do it!

Fun Products: Water-Absorbing Crystals

In preparation for some Halloween fun, you might want to consider getting your hands on some water-absorbing crystals.  They come in a variety of names and can be found in all sorts of locations.  In short, you're looking for a small crystal that can absorb large quantities of water. 

Sodium Polyacrylate is the polymer used in diapers to absorb large quantities of liquids.  You can get it from Educational Innovations, among other sources.  It's great for "disappearing" water magic tricks.  You have a small amount of the powder in a cup.  Pour in some water and a minute or so later, turn the cup upside down and nothing comes out.  (For your performance, you'll want to use an opaque cup, but I wanted to let you "in" on the action).

Ghost Crystals (also available from Educational Innovations) are lots of fun. This are much larger crystals than the sodium polyacrylate.  After you've enlarged your crystals, very carefully tie a thread around a single crystal.  Fill a water bottle with water and submerge the crystal, on its leash, in the water.  Leave the thread hanging over the side of the water bottle and screw on the cap.  Tell your students you've brought your ghost pet to visit for Halloween day.  They'll look and look, but all they'll see is a leash suspended in the middle of the water! 

It's also fun to trick your student with some "chunky" water.  A clear container filled with the enlarged crystals and a small amount of water will look just like a glass of water.  Fill a pitcher with the polymers and offer to pour a student a glass of water - instead of a stream of water, chunks will come out of the pitcher.

Other places to find water-absorbing polymer crystals:
Steve Spangler's Water Jelly Crystals look to be of a similar size to the ghost crystals, if you prefer to shop there. 

I've seen similar products (I'm not sure of their exact chemical make-up, but they function in the same way) at:
Toy stores (random locations within the store)
Garden centers (as an additive to retain moisture in soil)
Craft Stores (usually in the floral area)
Science supply catalogs

Lots of fun for Halloween or April Fool's Day, but also useful when studying polymer chemistry!

Update: Momentum in a Collision

Last winter I shared my Momentum in a Collision activity with you, in which students used rulers to create ramps down which they rolled marbles of varying sizes to observe the transfer of momentum in action. 

Since then, I've had a brainstorm of another, more qualitative way, to complete the activity.

If you know of any young train fans, see if you can get your hands on their wood train tracks, especially the rise-and-fall tracks. 

The parallel grooves on the tracks allow you "run" two marbles at a time and compare the transfer of momentum as they crash into different sized marbles at the end of the hill. 

Train tracks also give you the opportunity to create a nice long runway for the marbles to roll along until they run out of energy. 

The Ivory Soap "Explosion"

I absolutely love it when I learn a new science trick.  At this point, I've seen quite a few, and while there are always new-and-improved versions out there, it's not too common for me to come across something brand new.  Which is one of the reasons I love this demonstration (and it's just SO cool).  It's apparently a well-known demonstration, but I've missed it up 'til now.  (And that's another reason why I make a point of sharing the "classic" science experiments that so many have already seen - everyone has to learn about them for the first time, some time). 

On with the demonstration....

Begin with a bar of Ivory soap (or you may want to use a sliver of soap.... you'll see what I mean). 

Make the appropriate observations of the soap. 

Place the soap on a microwave-safe plate. 

Make a hypothesis* about what will happen when the soap is heated in the microwave.

Now heat the soap in the microwave - set the time for 2 minutes, but keep an eye on it (you'll be doing that any way, trust me).

Observe the soap carefullly.

The soap will expand to a huge volume.  If you use whole bar of soap, it will nearly fill the microwave!  Great wow factor! 



It deflated a little at this point, because my camera's batteries died at this point and I had to wait for them to recharge.



Why does this happen....

Remember when the Ivory floated because it had more air in it than the "other" soap?  When the Ivory is heated, the soap softens and the air bubbles expand.

How can you use this in your science class?

1. A follow-up to the previously mentioned density experiment.
2. A discussion of gas laws (Charles Law, specifically) - when a gas is heated, its volume will increase. 
3. A lesson on physical and chemical changes.  Explosions are chemical changes by definition.  This demonstration looks like explosion, but it's not.  It's just a physical change. 

*A funny story - I told my 5 year old that we were going to do a science experiment after dinner.  He asked what we were going to do and all I would tell him is that we were using soap.  Then I asked if he had any hypotheses about what would happen to the soap (knowing absolutely nothing about what we were going to do to it) and he said "It's going to explode."  I think he was a little surprised at how close to right he was!

Light: Refraction: Flip an Arrow

This is a great way to kick off your study of refraction and lenses.

Provide students with a cylinder of water (without lines, words, etc. on it - check your recycling bin for empty glass bottles) and an index card with an arrow printed on it. 

Have the students observe the arrow, looking through the cylinder of water.  What happens as the move the arrow away from the water? 

How about when the move the arrow closer to the water. 

The cylinder of water is acting as a lens.  When the arrow is close to the lens, it is magnified, but pointing in the original direction.  As the arrow is moved away from the lens, it flips. 

Provide students with plenty of time to play with these simple objects, allowing them to make as many observations as possible.  Some ideas to try out:

• watching the arrow through the water while the rotate the paper
• holding the arrow vertically instead of horizontally
• observing other shapes or letters through the lens

Once students have gained some hands-on experience with this simple lens, head back to the desks to work on explaining what was witnessed with words and diagrams. 

Conservation of Energy: Your Own Astroblaster

You may have seen one of these toys around... A stick with 5 bouncy balls staked on top of one another.  You drop it on the ground and the top ball goes flying sky-high.

You can do your own demonstration, on a larger scale with balls you probably have scattered around your house (or that you could borrow from the phys. ed. teacher).

I'm using a squishy mini-soccer ball stacked on a basketball.  They're both a little flat, and only bounce up to about my waist when I drop them from chin height.

But, if I stack them on top of each other and drop them, the soccer ball goes flying off, reaching an altitude many times higher than when dropped by itself.  The basketball doesn't bounce back much at all.  Just a little, and then it rolls away. 


The soccer ball went much higher than that - my camera timing skills aren't perfect!


This is a demonstration of conservation of energy and momentum.  Nearly all of the energy the basketball had is transferred to the soccer ball - allowing the soccer ball to fly off with more energy than it started with and the basketball, left with almost nothing, just rolls away.

You can have lots of fun experimenting with different balls - golf balls, ping pong balls, super balls, playground balls, etc.  What do you think would happen with 3 balls?  Give it a try!

Find the Center of Gravity

This activity makes me happy because it reminds me of the one activity I distinctly remember from high school physics with Mr. Eide, master of the pun.  We used large pieces of Styrofoam and a soldering iron (I think) to make the holes.  This version is safe to do with young students and the materials are easier to come by.

Before hand...

You'll need to make a plumb line (or several). 

Cut a length of string, about 12 inches.  Tie a metal washer to the end (or a fishing sinker or anything else that's heavy and can easily be tied to the end of a string).

 Tie the other end of the string around a pushpin.

The activity...

Cut one side of a manila folder into an irregular shape

Punch five holes (randomly spaced) at the edge of the shape.

Stick the pushpin (with the plumb line attached) through one of the holes and hang it on a bulletin board.  The shape and the string should both swing freely.

When everything has stopped moving, use a pen to draw a line on the paper along the string.

Move the pushpin to another hole and repeat. 

Continue until you've used each of the 5 holes. 

Take the shape down.  The five lines intersect in one point.  If you place your finger under that point, the shape will balance perfectly.  You've located the center of gravity for your shape!

And, if you move your finger, even a small amount, from that spot, the shape will tumble to one side or the other!

Periodic Table: Sticker Atoms

Each year, aAfter my students had learned about atomic structure and were beginning their periodic table investigation, they each chose an element to research a bit.  Every year I varied the product they produced a bit - variations on the element models and an element block (watch for more information on that one coming soon). 

One year, in addition to making their block, I had them create a sticker picture of their element. 

Each student was given a piece of black paper, blue dot stickers for protons, green dot stickers for neutrons, tiny smiley face stickers for electrons and a white colored pencil. 

Making the picture was not particularly challenging - though some interesting questions did arise about electron orbitals for students who were doing transition metals. 

The reason for making the picture wasn't in the interest of challenging the students, but instead to create a giant periodic table.  I laminated each of the individual pictures and then assembled them using clear packing tape. 

This periodic table does a nice job of showing the enlarging nuclei and increasing electron orbitals.  And by taking part in making the table, the students were much more invested in the process and obtained greater understanding of how their element fit in the periodic table.

FYI:

I had three classes of students and each student had to choose a unique element.  Each class was informed of the parameters during class time and element choosing "opened" at the end of the school day - so each student had equal opportunity to have the first choice.

In addition, I had a few students who helped make pictures for some of the elements that weren't chosen, so we had a more complete periodic table - at least for the first several periods. 

Inertia: The Non-Rolling Marble

To prepare:

Glue a thin washer onto a piece of paper.

Set a marble in the washer.  Quickly pull the paper out. 

If you move quickly enough, the marble will remain where it was.

Summer Science Camp: Hovercraft

The summer we offered a middle school version of science camp, we had fun making hovercrafts.  The "teacher-versions" were the full 4' (diameter) circles.  We had a handful of kids and they each made their own from a 2' (diameter) circle of plywood.

We followed Daryl Taylor's instructions, which I'll let you read on your own. 

In short:
The hovercraft is basically a large circle of plywood covered with plastic.  A shop vac motor (one whose motor can be switched to blow) is attached to the craft.  The motor pushes air into the space between the wood and the plastic, creating a buble.  The plastic has several small holes in it - the air is forced out of those holes and in turn the craft is pushed up, hovering above the ground.  Left alone, the hovercraft will stay in one place - add an outside force and you'll start to see physics laws in action!

Here are some pictures to aid in your construction (sorry, no action shots - go here to see Daryl's in action).

The bottom side:

In the center you'll place something to hold the plastic down.  Most people would use a plastic lid, we used something my friend's husband had lying around in his workshop - I'm not even sure what it is! 

You'll notice that ring of duct tape - it's not just decorative!  It reinforces the plastic, so you can cut holes in it without shredding the whole thing.



The top:

A masterpiece in duct tape:

It really does take vast amounts of duct tape to make sure the plastic is held down and no air will leak out. 

In the above picture, you'll notice a small hole cut out, near the bottom of the picture, slightly to the left.  That's where your shop-vac hose will connect to the hover craft, turning it from a heavy-piece-of-plywood-covered-with-duct-tape into a hovering-piece-of-plywood-covered-with-duct-tape!

It's not the most beautiful contraption ever, but it is a very cool demonstration of all kind of physics principles and it really does work!

Summer Science Camp: Sharpie T-Shrits

This is both a Summer Science Camp idea and a previous-post update.

The pinwheel Sharpie t-shirts are a great summer science camp project.  Take the shirts, markers and rubbing alcohol outside and get creative.  Bonus: when you're outside there's less worry about alcohol fumes bothering anyone!

The update: when I was getting ready to do this project with a group of 24 students, I was trying to find some enough of the same type of container to stretch the shirts around, without making a huge investment. 

I decided to with with 4" PVC pipe (available from hardware stores), cut into 5 or 6" lengths.  You do need a hacksaw to cut the pieces, and the cutting can be a bit messy, so you'll have to determine if this option makes sense for you. 

It worked quite well for several reasons:

• The tie-dye designs don't usually go beyond 4", so it was plenty large.
• The smaller size (as compared to a shoe box or dish pan) made it easier for young hands to manipulate and stretch the rubber band around.
• The smaller size was nice for students sitting almost shoulder-to-shoulder at tables. 

The pictures included in this post are of shirts created by students in grades 3 through 5.