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!

Erosion: A Flowing River

This is a good one to do outside, if you can swing it.  If not, it can be done inside, you'll just need to work harder to contain the water.

Materials:

--Paper cup

--Drinking straw
--Clay
-- Cookie sheet
--Loose soil or sand
--Jug filled with water (or other water source)

Prep Work:

Poke a hole in the side of the paper cup, near the bottom. 

Cut the straw in half and place one half in the hole.

Seal the hole, around the straw, with the clay.

For the Demonstration:

Lay the cookie sheet upside down on the ground and raise one end about 2 inches, using scrap wood, a brick, a pile of soil, whatever's convenient. 

Cover the cookie sheet with a thin layer of soil or sand. Place the cup at the raised end of the cookie sheet.

Hold your finger over the straw as you fill the cup with water. Remove your finger and watch the way path of the water.

Raise the end of the cookie sheet to about 6 inches, recover the sheet with soil and repeat.

What differences did the slope make in the erosion?

Cover the cookie sheet with a layer of soil again.  This time, place a small rock  in the soil in front of the straw. 

Fill the cup and watch what happens to the water as it encounters the rock.  You can place additional rocks along the way to change the direction of the river.

Body Systems: Skeletal System: Bone Model

I was inspired by the edible bone models I've come across, to create a non-edible bone model I could keep in the classroom for use year after year, and pull out at a moment's notice.  The supplies are readily available at hardware stores and craft stores.  I hope you find it useful. 

You'll need:
~10" foam pipe insulation
~10" 1 1/2" PVC pipe
Model Magic clay
red yarn
fabric pieces

Begin with the length of foam pipe insulation to use as the spongy bone.  Split the insulation open to reveal the hollow tube in the center, perfect for holding the bone marrow. 

Roll the clay into a snake that fits the center of the pipe insulation.  While you're rolling the clay, embed a length of red yarn in the clay to represent a blood vessel traveling through the marrow.

Slide the completed spongy bone and marrow into the length of PVC pipe.  This is the compact bone. 

Use the fabric to create a tube into which the PVC pipe can slide.  This is the membrane covering the bone. 

I added a few pieces of Velcro, to attach the blood vessels. 

And finally, wrap the outside of the fabric with additional lengths of red yarn - more blood vessels.  (I should add some blue yarn as well....)

I'm really quite pleased with my model.  It can be taken apart and put back together again and again and I think it will be quite useful in the classroom.

Because you usually have to buy 10' lengths of PVC that you have to cut yourself, some of you might be turned off by this project.  I've got extra materials from making my own, as well as easy access to additional supplies, and a willingness to make up some additional models.  If you're interested in purchasing a pre-made model (or several), send me an email and we can discuss the details.

Body Systems: Skeletal System: Why You Need Calcium

For this demonstration, you'll need a clean chicken bone* (a drumstick works best) and a large jar filled with vinegar.  You'll also want some way to close the jar, either a lid or some plastic wrap.

Observe the bone, try to bend it (but don't actually do so, you want to keep it in one piece).

Place the bone in the vinegar and cover the jar.

Remove the bone from the vinegar every day for about a week.  Observe and test for flexibility.


Over the course of the week, the bone will become more and more flexible, taking on a rubber-like feel by the end.  The vinegar (acetic acid) breaks down the calcium deposits in the bone, allowing you the opportunity to observe the importance of calcium in maintaining bone strength.

**The next time you have chicken or turkey, you may want to clean the bones and stick them in a resealable bag in the freezer, so you have them when you need one.

Flatten an Index Card

Challenge your students (or family members or friends or anyone else you encounter) to find two ways to flatten an index card, without touching it.

To prepare, fold an index card in half and set it on the table to make a tent. 

Your challengee will likely immediately blow on the top of the card to push the middle down.

The challenge comes in finding a second way to accomplish the task. 

It's time to put your knowledge of Bernoulli and air pressure to work!  By blowing under the card, you'll move those air molecules out of the way, allowing the air molecules on top of the card to push the card down.

Density: Ivory Soap vs. "Other" Soap

Another simple demonstration involving density....

Show the students a bar of Ivory soap and a bar of any other brand of soap.  Ask for predictions about what will happen when the bars are placed in a tub of water.  Float or sink?  Will the both do the same thing, or will they do different things? 

Then put the bars in the water, using as much flair as you deem necessary.

The Ivory soap will float, but the other soap will sink. 

Of course, now the work begins and it's time to hypothesize why the difference.

I'm sure your students will come up with all sorts of possibilities (the more the better), but the reality is that Ivory whips more air into their soap a they're making it.  More air pockets = lower density. 

You could have the students calculate the density of each of the bars.  If you're using nice rectangular bars, the volume can be calculated using dimensional measurements.  If you're using a funky shaped bar of soap, as this bar of Zest is, you'll need to use water displacement to get the volume.

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!

Air Pressure and Bernoulli:Clanging Cans

This demonstration is very similar to the balloons and the cardboard tubes.

There are two ways to try this one:

Version 1:
First, lay two empty soda cans on their sides a few inches apart, parallel to one another.

Blow between the cans and watch them roll together.  It happens because you've pushed the air molecules that were between the cans out of the way, so the air pushing on the opposite sides of the cans is unbalanced and the roll together.

Version 2:
Set up a bunch of straight straws parallel to one another, about half an inch apart from one another. 

Set the two cans upright on the straws, a few inches apart.

Blow between the cans and watch!

Tornado: Make Your Own Tornado Tube

I'm sure many of you have seen the little tube/connectors you can use to connect two 2-liter soda bottles to make a tornado tube.  Like this:


I've wondered at various times, whether one could create the tornado tube without that little plastic connector, which I don't happen to possess, and while quite inexpensive, have never gone ahead and purchased.

I was pleased to find instructions for creating my own tornado tube in Janice VanCleave's 202 Oozing, Bubbling, Dripping, and Bouncing Experiments.

The materials you'll need:
--a flat metal washer - one that's the same size as the mouth of the bottles
--duct tape
--two 2-liter soda bottles

Fill one of the bottles half-way with water (feel free to add a little food coloring and/or glitter, if the mood strikes you).

Dry the mouth of the bottle well.  Place the washer over the mouth of the bottle.

Place the second bottle upside down, on top of the washer.

Tape the bottles together with the duct tape - don't skimp, make sure things are secure!

Turn the bottles upside down.  With one hand on the top bottle and the other on the bottom, move the top bottle in a small circle.

Set the bottles down and watch the tornado vortex form.

I was pleased with how well the tornado formed.  However, despite my best taping effort, some water leaked out every time we used it.  If it's something you're going to do repeatedly, it's probably worth a couple bucks for the special coupler.  If it's likely a one-time thing, this definitely works and is less "stuff" to have around the house.

Air Pressure: Plungers!

On a large scale:

Get your hands on two plungers - new and clean would be preferable (I've actually seen small ones, perfect for this demonstration, at a dollar store)! 

Match up the edges and push the plungers together.

Now try to get them apart.  Not an easy task! 

You pushed all the air out of the middle, so there's nothing pushing them apart.  Only lots of air on the outside pushing them together.

In the end, if you have a good seal, you'll need to force some air in to break the seal, but splitting the plungers apart.

On a smaller scale:
You can have your students perform this activity themselves using suction cups (the kind you sometimes use to hang things in your windows).  The physics is exactly the same, just smaller!