Body Systems: Cardiovascular System: Components of Blood

This is a fun way to review the parts that make up blood.

Plasma

Makes up 55% of your blood.  It's a thick liquid that carries that transports food and waste.

Fill a clear glass/jar/beaker 55% full with corn syrup.

Red Blood Cells

Make up 44% of your blood (by volume).  These cells carry oxygen and carbon dioxide throughout your body.

Add candy red hots to the corn syrup, until the container is nearly full.

White Blood Cells
These cells are significantly larger than red blood cells, and there are far, far fewer of them in your blood.  These cells clean-up old blood cells and fight the germs that enter your body.

Add a few mini-marshmallows or white jelly beans to your concoction.

Platelets

These are tiny fragments of cells (some books will just refer to them as cells) are responsible for forming clots when you are cut.

Shake some non-pareils into your blood model.

You now have a cup of "blood".  You'll notice that much of it is liquid, but there's lots of solid in it as well.  You'll also notice lots of red blood cells with the occasional white blood cell popping up.  You have to look really hard to see the platelets - both because of their small size and because of their small numbers. 

Oceans: Increasing Pressure with Depth

Students don't always understand that the deeper you go under water, the greater the pressure.  This immense pressure is one of the reasons why so much of the ocean floor is still unexplored. 

Try out this demonstration to help your students visualize the pressure increasing as they travel deeper.

Begin with an empty carton from a half-gallon of milk or OJ.  (A bottle would work too, but it's much more difficult to make the holes). 

You'll also need some masking tape, a large tub in which to collect water and a poking device - I found a skewer worked well for me.

Lay the carton on its side on the table and make a hole near the bottom of the carton.

Make a second hole 1 - 2" above the first hole and a third hole 1 - 2" above the second hole.

Run a strip of masking tape down the carton, covering all three holes.

Fill the carton with water and set it on the table, with a tub to catch the water when it spills out of the holes. 

When you're ready, remove the tape and observe the water flowing out of each hole.

The water coming out of the bottom hole is under the greatest pressure (it has the most water/weight on top of it) and it is pushed out of the carton with much greater force - look how far it shoots out.

The water coming out of the top hole is under little pressure (there's not much pushing on it), so it sort of dribbles out.

Dissecting a Diaper

Mystified by the amount of water a single diaper can hold? 

If you've got a few extra diapers laying around after last week's experiment, consider dissecting one and to learn what's inside. 

You'll need a diaper, a pair of scissors, and a zip-top bag.  You may also find it convenient to work over a black piece of paper.

Begin by cutting a slit in the diaper.

Pull the "stuffing" out of the diaper and place it in the bag. 

At this point, you may feel some small granules, and notice white powder gathering on your piece of black paper.  These are sodium polyacrylate crystals - the magical component of disposable diapers. 

You can gather additional crystals by sealing the bag and shaking it for a minute or two. 

While shaking, the crystals should separate from the cotton and settle at the bottom for the bag. 

Once you've isolated the crystals, you can experiment with them (though you won't have very many from a single diaper).  See how much water they absorb.  Or try one of the water-absorbing crystal tricks mentioned here. 

Again, it could be interesting to compare the crystals found in different brands of diapers - are they all the same size, do they come in the same quantity? 

A good scientific exploration to learn more about the world around us, and also an introduction to polymer chemistry!

Happy Thanksgiving!

Many heartfelt thanks to each and every person who takes the time to read the ideas I share.  And many additional thanks to those of you who take a few extra moments to add a comment or otherwise provide feedback. 

Readership has been growing, making it very exciting to keep on blogging, even when I'm feeling challenged to come up with ideas to write about.  Thank you for spurring me on and keeping this little "hobby" going. 

I hope each of you has a wonderful Thanksgiving holiday filled with good people and good food!

Proceed!

Okay, the practice quiz has been fixed (I think!) - it's now a multiple choice quiz instead of fill-in-the-blank, which will not only make it easier, but should make the programming work appropriately.

Thanks to the early testers who let me know there was a problem.  I'm so glad I went ahead with the practice version!

Here's the link to go to the fixed quiz.

Practice up! - But not yet!!

Sorry - there's a problem with the practice quiz that I need to try to fix.  I have to run out at the moment, but will get to it as soon as I can.  Will let you know when it's back up and running. 

Practice up!

I'm finalizing the Natural Things quiz for sometime next week. 

Did I mention, there's a prize involved?  It's a good one!

In the meantime, I've made a simple little practice quiz - practice for me in making the quiz and gathering the data and practice for you to use the quiz format. 

If you have a minute (literally, you should only need a minute), hop on over and take the quiz - it makes no difference if you answer the questions correctly or not!

Click here to take the practice quiz now!

Atmosphere: Play Doh model

Begin with 5 (or 4, if you take your photographs without going back and looking at your own directions... sheesh) equal sized balls of Play Doh.  Color is unimportant in this model. 

Place one ball on a piece of wax paper, this is the troposphere. 

Place a heavy book on top of the Play Doh.

Place another ball of Play Doh on top of the book, this is the stratosphere.

Place another heavy book on top of the Play Doh. 

Continue alternating balls of Play Doh and heavy books until you've accounted for the 5 layers of the atmosphere. 

Then unstack the books.  You'll find that as you move closer to the Earth (the bottom of the stack), the layers become thinner.

Scientific Method: How Much Water Can a Diaper Hold?

A different, and very intriguing question to try to answer using the scientific method. 

For a basic investigation, you only need a diaper, water* and graduated cylinder (or measuring cup).  Just for fun, you could add a drop of yellow food coloring to your water supply... it might completely gross you out, but middle school boys will be completely sold on it!

Open the diaper and pour 100 ml of water onto it. 

Hold the diaper by the ends and gently rock it back and forth until the water is absorbed.

Continue to add water, in 100 ml increments until the water is no longer absorbed. 

To take the experiment one step further, you can compare the absorbency of different brands of diapers.  Make sure you use the same size diaper for each brand.  After gathering your results, you could even determine the diaper cost per mL of water held!  Do the more expensive diapers hold more water?  Remember, for the most accurate results, you should test several diapers of each brand. 


*I've always seen this basic experiment done with plain water.  But, if you'd like to simulate urine, mix 9 grams of salt into a liter of water and use that solution.  I've read that the diaper will perform differently with this solution than with straight water.  That sounds like an experiment worth trying! 

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. 

Body Systems: Digestive System: Peristalsis

Although gravity aids in the swallowing of food, it doesn't work alone.  Our body actively pushes each food bolus through the digestive system, a process called peristalsis. 

Here's another hands-on model to help your students get a feel for peristalsis. 

The esophagus is made from a leg from a pair of tights or pantyhose.*

Cut the toe off in order to create a tube.

The food bolus is represented by a large plastic egg. 

Place the egg in one end of the tube.  Hold the 'esophagus' vertically so students can see that the food will not just fall through the esophagus - it's going to need a little help.. 

You can return the set-up to the table and have students determine the best way to move the food through the tube. 

They will quickly realize that the egg moves best when the tights/pantyhose above it are squeezed.

This is comparable to the muscles in the esophagus constricting and pushing the food throughout the digestive system.

Of course, we usually consume more than one bolus of food, so you can provide your students with a whole basket of eggs they need to get through the digestive system.  Create several set-ups and have teams of students race!


*Remember the plastic eggs that pantyhose used to come in, back in the day?  Those were the eggs I saw used in this activity originally.  I don't believe you can find those any more (at least without purging your grandmother's house), so I used a large-sized plastic Easter egg.  It works well, though its smaller than the original prop, and as such, you might want to use a child-sized pair of tights to make your esophagus. 

Plate Tectonics: The Break Up of Pangea Flipbook

Have your students watch Pangea break up, while making a flip book.

Professor Braile (Purdue University) has done the hard work - you simply need to copy the maps onto cardstock (for the best results) for your students.  They color and assemble the maps in the proper order. 

Salt Water Painting

Make a batch of super saturated salt water*.

Fill a shallow pan with the salt water.  Cut pieces of paper smaller than the pan, any shape you like.

Drip food coloring onto the water and swirl with a toothpick.


I'm not sure why the red dye looks so metallic in the photos...


Quickly place a sheet of paper on top of the coloring.  When the paper is wet, pick it up and lay flat to dry.

The salt water is much denser than the food coloring, so the coloring floats on the surface, at least long enough to complete this project.  Given time, the food coloring will disperse in the salt water.

*Fill a jar part way with hot water.  Add some salt and stir.  Keep adding salt and stirring until no more salt dissolves (you see the salt sinking to the bottom).  Let it sit for a few hours.  Then pour off the clear water - the super-saturated salt water solution.

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!

Cells: Semipermeable Membranes

You don't have to get very far into your study of cells before your students are presented with the term "semi-permeable," used to describe cell membranes.  Just as easily as you can define it for your students, you can show them!

Before class mix together 1/2 cup of sand (or salt) and 1/2 cup of marbles (or dried beans, pebbles, or other objects larger than the holes in a colander).  Place the mixture in a beaker or glass jar.

When you get to semi-permeable membranes during class, show the students your mixture.  Then pour the mixture through a colander (make sure you have a bowl or pan underneath!).

The beans stay in the colander while the salt/sand passes right through.  Just like a cell membrane, particles that are small enough to pass through the holes do so and particles larger than the holes stay put.

Weathering: By Falling Water

One of the ways in which rocks are weathered (broken down into smaller pieces) is by falling water.

Place a bar of soap on a sponge.  Set the sponge in a sink under a faucet.

Use the faucet as usual for a day, letting the water hit the soap and observe the soap at the end of the day.  Or you could let the faucet drip on the soap for the duration of the class period.

The falling water knocks particles of soap free.  Similarly, rocks at the bottom of waterfalls (or in other locations where water falls over them) are weathered by the falling water over time.  Of course, this process takes a very long time since rocks are lots harder than soap!

Air Pressure: Egg into a Flask

This is another classic! 

In preparation for this demonstration, you'll need to hard boil some eggs.  When cool, peel them. 

You'll need a flask or bottle (Snapple bottles are a good size) with an opening that's smaller than the egg (the egg should be able to sit on top of the opening.  You may wish to grease the opening a little to help the process, but it usually isn't necessary.

To perform the demonstration:

Light a small piece of paper on fire with a match or lighter.  Drop the paper into the flask/bottle.  Quickly place the egg on the opening.  Watch.

The fire will extinguish when all the oxygen has been consumed.  And the egg will slowly work its way into the bottle/flask.

Since the oxygen has been consumed, there is less air in the flask, so the air pressure outside of the flask pushes the egg in. 

(At this point, you're probably looking for an additional picture.  My camera went on hiatus, so there is no picture, but I can tell you that my egg was too large for the bottle I had on hand, so even if I had a picture, it wouldn't look terribly different from the one above.)

There are ways to use air pressure to get the egg out, but I can never get them to work.  Instead, I break up the egg with a knife and dump it out.  Not as dramatic, but it works!  If you're interested in trying it for yourself, do a Google search and you'll find numerous sites with directions.

You'll probably want to try this demonstration once before performing, to check that your bottle/flask opening and egg are a good size match.  (See above).  Of course, eggs are all slightly different sizes, so there's no guarantee that you won't get the egg stuck in the neck of the flask, but it should give you a good idea!

Natural Things Swap Update

Swap boxes are getting packed up to head out to their recipients early next week.  (If you're not familiar with the Natural Things Swap, you can read more about it here).

Thanks to everyone who participated - each and every person who said they wanted to play along made me so happy!

If you missed out on this year's swap, you'll have a chance to play along virtually in the coming weeks - there will even be prizes! 

Keep watching for more information!

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!