Weathering: Plant Roots

 

Plants, specifically plant roots, are one source of weathering.  Cracks in driveways and sidewalks often provide evidence of this, but it's simple to watch it take place within your classroom. 

You'll need some Plaster of Paris*, seeds** and a small disposable cup or cupcake paper.

Mix the plaster according to the package instructions (usually 2 parts plaster to 1 part water).  Pour the plaster into your vessel. 

Poke two or three seeds into the plaster.  Place in a spot where it won't be disturbed while the plaster sets and the seeds germinate (there's enough moisture in the plaster for the seeds to begin germinating, no need to add anything). 

Within a day my seeds had swollen and begun to germinate.  The force the seed exerted was enough to crack the plaster. 

Now think about what happens in a driveway or sidewalk... a crack forms in the surface, seeds blow or fall into the crack, a bit of rain falls and the seeds begin to germinate.  The force of the seed germinating and the roots taking hold forces the more cracking.  Now there's a larger crack into which more seeds can gather and cause further cracking.  If nothing is done to curb the problem, eventually the sidewalk or driveway will be dessimated. 

*FYI Plaster of Paris does have a limited shelf life.  If it gets too old, it won't set up properly and you'll have a crumbly mess.

**I've mentioned it before, but dried beans (like you'd use to make soup or baked beans) will germinate.  They're cheaper to buy in a large quantity than garden seeds and they can be found easily year-round.

Conservation of Matter: Steel Wool & Vinegar

This is another versatile demonstration to use in your student of chemistry - learn about chemical changes, chemical reactions, conservation of matter and even air pressure.

Depending upon the take-home message you want your students to get, you might structure the activity in a few different ways, but the basics are the same.

You'll need some steel wool, vinegar, bottles or flasks and a balloon.

Pull apart some strands of steel wool and push some into each bottle.  Pour some vinegar onto the steel wool.  (Some instructions tell you to soak the steel wool in the vinegar for a few minutes and then remove the steel wool.  I just left mine in it).

Stretch a balloon over the opening of one bottle, but leave the other as is.

You could find the mass of each system at this point, if you're interested in conservation of matter.

Allow the bottles to sit and the reaction to occur. 

The vinegar removes the coating from the steel wool, and the steel will be begin to oxidize in the presence of oxygen. 

As the reaction is occurring, the balloon will be pushed into the bottle.  Why?

The oxidation reaction is using up the oxygen in the bottle, which will lesson the number of air molecules in the bottle, thus reducing the pressure in the bottle.  Because the pressure outside the bottle is greater than the pressure inside the bottle, it will push the balloon in. 

You can stop there if you're interested in simply looking for evidence of a chemical change, studying the chemical reaction or seeing the affects of air pressure. 

If you're interested in conservation of matter, continue on. 

Find the mass of each system once again.

The closed system (i.e. the one with the balloon covering the opening), should have the same mass it had in the beginning. 

The open system's mass should have gained mass, as it continued to pull more oxygen into the system to carry out the reaction further. 

Erosion & Run-Off: What affect does vegetation have?

 This is a really simple demonstration, but it does require some planning ahead (not always my strong suit... )

You'll need two shallow pans or boxes.  Fill each pan with dirt.  Sprinkle grass seed on one of the pans of dirt.  Keep the soil moist as the grass seed germinates and grows.  (You don't need to do anything with the other pan of dirt right now).

Once you have a nice crop of grass in the one pan, take both pans outside.  Prop up one end of each pan using bricks (or something else that will raise it a few inches).

Begin to spray both pans with a hose or spray bottles of water.  You can spray in any manner you'd like, just try to get both pans equally.

While you're spraying, observe what happens to both the soil and the water in each situation. 

When you've finished, discuss the impact of vegetation on soil erosion and/or water run-off. 

The Expanding Universe: Balloon Model

 On a flat, not-yet-inflated balloon, mark a series of points using a permanent marker.  You may wish to make some of the points closer together and others farther apart. 

These marks represent parts components of the universe.  You may wish to have students measure the distance between points to make it more quantitative, of you may wish to just keep it a visual activity. 

 As you begin to inflate the balloon, the points mover farther and farther away from each other.  The universe is expanding and distance between points is growing. 

Cells: The Importance of Cell Walls

 Cell walls prevent plant cells from bursting. 

Blow up a balloon until it pops.  An animal cell (or a plant cell that's missing a cell wall for some reason) is like this balloon.  Water can flow into the cell until the membranes bursts. 

Now place a balloon into a length of pantyhose and proceed to blow it up.  It will be harder and harder to blow up the balloon because the nylon restricts the balloon.  Virtually impossible to blow it up enough to pop it.  In the same way, the cell wall prevents the cell from reaching its bursting point. 

Newton's 3rd Law: Popping Canisters

 This activity can be done as one activity in a series of stations on Newton's 3rd law, or it could be done as a demonstration if performed on an overhead projector* (does anyone still have those in their classrooms?!?!)

You'll need 2 film canisters (another relic), Alka-Seltzer, water and a pan with a line drawn down the center. 

I took the set-up picture with the transparent canisters, but later switched to the black**

Fill both canisters about half full with water.  You'll want to have the same amount in each canister.  

Cap one of the canisters and lay it on its side so the cap is against the line in the pan. 

For the next portion, you'll need to work quickly....
Add about 1/4 - 1/2 of an Alka-Seltzer tablet to the second canister and cap it.  Then lay that canister so its cap is against the line in the pan. (The two caps should abut one another). 

When the Alka-Seltzer creates enough gas to fill the canister, it will pop the top off.  At the same time it will push the second canister.  Equal force will be applied to each canister, but in opposite directions.  After the explosion, the two canisters will end up in mirrored positions.  

*If you want to do it on an overhead projector, draw a line down the center of a transparency using a permanent marker.  And use a minimal amount of water.  

**This is definitely a demonstration to play around with before you plan to do it in front of your students!  I've done it successfully several times in the past without problems, yet when I went to photograph it, I ran into problem after problem.  The first canisters I grabbed to use leaked so that enough pressure never built up to pop the top off.  Then I used too large a piece of Alka-Seltzer and sent the canister flying out of the pan and off the table (fortunately it didn't go through the brand-new dining room window!).  It's a great little activity, just give yourself a chance to practice it in advance! 

Tsunami!: Tsunami Demonstration

Tsunami! is the story of

If you're feeling ambitious, you can make a very cool tsunami demonstrator following the directions found here. 

If you're not up for such a task, you can make simpler models using 2 liter soda bottles.  While this simpler model probably doesn't have the same impact as the fancier versions, it does have the added bonus of allowing students to take part in its construction and manipulation.

Fill the 2 liter bottle with about 2 inches of gravel.  (I used sand because I had it on hand, but gravel works MUCH better).

Then pour about 250 ml of water (about 1 cup) into the bottle.  Cap it tightly.

Gently lower the bottle to its side, so the gravel forms a slope at the end of the bottle (you'll see that the sand doesn't work so well at this point, in the picture below).  The gravel slope represents the sea floor and then the beach.  The water represents the ocean.

Use the palm of your hand to smack the bottle cap (i.e. the end of the bottle opposite the gravel slope), to generate a wave.

Observe the wave formation and the way it crashes upon the gravel.  Also note the way the water sloshes around on the gravel following its initial crash - the danger of a tsunami extends beyond the initial landfall. 

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.

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.

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. 

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.