Air Pressure: Bell Jar Demonstrations

If your school has a bell jar and vacuum pump, break them out!  Try some of my favorites:

- 1 -
Fill a small beaker part way with water.  Have some students touch the water - it's cool/room temperature.  Place the water in the jar and turn on the pump... the water quickly boils.  Remove the water and have students touch it again - it's still cool/room temperature!  With no air pressure, water boils at room temperature! 

 - 2 -
Fill a small balloon with just a small amount of air (just enough so there's air in there, not enough to even stretch the balloon).  Place the balloon in the jar and turn on the pump.  The balloon will expand!  Without air surrounding it, the air molecules trapped in the balloon will begin to expand, thus expanding the balloon!

 - 3 -
Place a marshmallow in the jar and turn on the pump.  The marshmallow will grow right before your eyes!  It's like the balloon above - there's air trapped in the marshmallow that expands when outside air pressure is removed.  Eventually the sugar structure will be stretched to its breaking point and the marshmallow will stop expanding.  When you return the air pressure, the marshmallow will be completely crushed - there's no structure to support/trap air molecules any more.

For some extra fun, pick up some extra Marshmallow Peeps during the holidays!

 - 4 -
Place a small dollop of shaving cream in a small beaker.  Set the beaker in the jar and turn on the pump.  The shaving cream will expand, out of the beaker and will fill the whole bell jar (be careful - turn off the pump before the shaving cream gets into the pump - that would be disastrous).  The shaving cream has air trapped inside of it.  It behands in the same manner as the marshmallow. 

You can also use whipped cream for this, but I find ath shaving cream cleans up very quickly and easily. 

**I've been told that you can do the marshmallow "trick" in one of the vacuum systems for food preservation (the kind that pulls the air out of a jar).  Not having such a system, I haven't been able to confirm, but that information came from a very reliable student.

Balancing Act

If you drop a paperclip into a cup of water, it will sink to the bottom, because paperclips are more dense than water.  But, if you're careful, you can take advantage of water's unique properties and make the paperclip "float" on the surface.  

Fill a cup with water - the fuller the cup, the easier to do this.

Use a fork to gently place a paperclip on the water's surface.  You want to place the whole paperclip on the water at one time.  You don't want one part of the paperclip poking through the water. 

This definitely takes some practice and can be a test of patience.  I have never been able to get more than one paperclip to rest on the surface of the water, but I've seen others do multiple paperclips at the same time. 

If you get frustrated watching someone else get their paperclips to stay on the surface while you can't, place a drop of soap in thier water while they're not looking...


Water molecules like ot stick to one another, creating a membrane-like surface across the top of the water.  If you place the paperclips just so, that strong surface tension will support the paperclips (they aren't actually floating - they are still more dense than water).  Soap breaks water's surface tension, so you won't get soapy water to support anything. 

Total Cereal: Iron Fortified

This activity can be used for several different curriculum areas: elements, magnetism and nutrition

Back in the day, Total cereal used to run a series of commercials in which a person had to eat a large number of bowls of their favorite cereal in order to get the same amount of vitamins and minerals they could get in one bowl of Total.  One of those nutrients is iron.  Check out how they fortify their cereal....

Pour some cereal into a cup or bowl.  Pour some water on the cereal and let it sit for 15-20 minutes; enough for it to get nice and soggy and too gross to eat.

Place a magnet (use the strongest magnet you can get your hands on - a regular magnet works, but the stronger the magnet, the better the results) in a plastic baggie*.  Then, use the magnet to stir up the cereal sludge.

When you pull out the magnet, you will find that you have small pieces of iron sticking to the magnet!  The cereal is fortified with iron filings!  Perhaps not the most usable form of iron for your body, but iron none-the-less.

*Putting the magnet in a plastic baggie serves 2 purposes:
 1 - It makes clean-up a LOT easier!
 2 - It can be hard to see the iron pieces on the magnet, but if you pull the baggie off and place it on a piece of white paper, the iron will be easy to spot!

Is It Living: The Martian and the Car

Images from Webweaver.nu 

There's a fun living/non-living scenario at Biology Corner. 

A quick synopsis:
A martian is sent to Earth to find evidence of life.  He brings back a car.  He's now on trial for not carrying out his duties. 

Have your students take on the roles of Defense Attorney and Prosecuter. 


I worked with a social studies teacher who was very interested in debate and mock trials.  She was always game for teaming up to turn this simple activity into something a little more involved and meaningful for the students.  Maybe you work with someone of a similar personality!

Earth vs. moon: Diameter Comparison

Draw a 40 cm (diameter) circle on your board.  [You could also cut out a 40 cm circle, but that takes a bit more work - you need to use a piece of poster board or tape several pieces of paper together].

Tell your students that that circle is the Earth (you could get creative and add some continents and oceans to your circle drawing to make it more convincing, if you're so inclined).  They now need to cut out a circle to represent the size of the moon.

Have the students tape their moons on the board around the Earth drawing.  Are the moons about the same size, or was there a lot of variation in the students' guesses?

The correct size for the moon is approximately 10 cm.  Measure the students' moons and remove all but the one closest to accurate (if there are none that are terribly close, you might want to remove them all and replace them with one of your own that's correct).

After comparing the size of  the Earth and moon next to each other, move the moon 1200 cm (12 m) away from the Earth - that's the distance between the two to the same scale.  Quite something, isn't it?

******
Presented by Dr. Christine Anne Royce (Shippensburg University) at the 2007 New Jersey Science Convention.

Inference Folders

One of the skills students need to develop as they learn to think like scientists is inferring. 

This is a simple activity to assemble, and is a good way to reuse old manilla folders and calendars.

Place a calendar picture inside a manilla folder; attach it with a piece of two of tape or a quick swipe of a glue stick.  Then, cut several small windows into the folder at various locations (cut on three sides, so you're left with a flap that can be opened and closed).  Number the windows in the order you'd like the students to open them.  Seal the edges of the folder with tape or glue. 

When students get a folder, they open the first window and observe what's inside.  Based on what they see, they need to infer what's inside.  They will then open the second window and add that information to what they previously gathered and refine their inference.  They will continue in the same manner until they've opened all the windows. 

At this point, your students will want to open the folder.  But, most of the time, scientists can't just "open the folder" - if they could, they wouldn't need to infer.  Scientists have to work with the information they have.  The best they can do is find ways to gather more information. 

Book: A Really Short History of Nearly Everything

http://science-mattersblog.blogspot.com/2010/06/books-short-history-of-nearly.html

I've previously espoused my love for Bill Bryson's A Short History of Nearly Everything.  This, A Really Short History of Nearly Everything, is the kid-friendly version of that book. 


This version uses text from the original (which I really like about it) and it adds lots of illustrations, many of them humorous, which fits right in with Bryson's writing style.  Of course the text is abridged to student-friendly length and content.  Each topic is given a two page spread, and like the original, you can open the book to any page you wish and dive right in. 

I think I would stick with the original for reading aloud to students, as the text flows better and provides more information  than in the Really Short version.  The text in A Really Short History of Nearly Everything is fragmented and interspersed amongst the pictures, which makes it difficult to read aloud (unless you're looking to share a single fact), but it's wonderful for students to pick up and page through on their own.