Microscopes: Elodea Lab

Elodea is an aquatic plant that can be found at most fish stores. It is great for looking at under the microscope because the leaves are so thin, only a couple of cell layers thick and light can pass through the leaf.

Place an elodea leaf on a clean slide. Place a drop of water on the leaf and then the cover slip. View under the microscope. You will note the regular, retangular shape of the plant cells, the cell wall, the chloroplasts, and the nucleus.

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.

Professional Development: Keystone Center

The Keystone Center is a non-profit organization that works to solve environmental, energy and public health challenges by bringing together leaders and acting as mediators in the discussions. 

In the interest of looking to the future and preparing future leaders, a large component of the work done by the Keystone Center is education.  They are an organization interested in teaching students how to think, not what to think.  They run a number of camps and programs for students and they believe in reaching large numbers of students by educating teachers. 

I had the opportunity to attend the Balanced Equation workshop, which is a day-long program devoted to learning about water quality.  The early part of the day was spent evaluating our prior knowledge and thoughts regarding water and the environment.  From there ran a variety of simple tests to evaluate water quality and we attempted to build our own water filters using common items.  The afternoon was spent trying out a number of water filtration devices currently used in country's/areas with poor water quality.  There was certainly a lot to be learned over the course of one day. 

Registration for the Balanced Equation workshop basically involved expressing interest and filling out a simple application. 

The Keystone Center's signature professional development opportunity is the week-long Key Issues Institute, which is held in Silverthorne, Colorado.  Like the other workshops provided by the Keystone Center, the Institute is provided to teachers free of charge (if you can get yourself there), but the application process is more competitive and you are by no means guaranteed a spot just because you're interested.  I do hope to have the opportunity to attend at some point in the future! 

Applications for the 2012 Key Issues Institute are available now, so you may want to head over and check things out.  I'm sure dates for the upcoming one-or two-day workshops will be available soon. 

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!

The Importance of Brushing Teeth - Part II

Last week we examined the importance of brushing your teeth as a preventative measure to defend against the acid found in foods.  This week we'll examine another way in which regular tooth brushing prevents problems - preventing tooth stains. 

This experiment is run much the same way as last week's.  You'll cover an egg with toothpaste, let it sit overnight and wash off the toothpaste the next day.

The egg is then placed in a cup of coffee (or strong tea).  A second, untreated egg is placed in a second cup of coffee.

The eggs are then allowed to sit and are observed over the course of the next 24 hours - or even longer if you wish.

You will notice that the untreated egg develops darker stains and develops them more quickly than the treated egg. 

You'll also notice that the treated egg does develop stains - the toothpaste does not completely prevent that from occurring, it just slows it. 

Untreated



Treated with toothpaste



So, when you brush your teeth,, you're building up protection against future stains as well as removing older stains.

Sand Collection

It's very simple to start a sand collection - every time you visit a beach or other sandy location, collect a small sample in a zip-top bag.  Ask your students to do the same on their travels, as well as colleagues and family members.  It won't take long and you'll have a variety of sand samples to compare and contrast. 

You can keep your samples in clear plastic bags and use a magnifying glass to observe, or if you've got the resources, you could store the samples in magnifier boxes.

The diversity of the samples will provide a variety of discussion points.  What is the sand made of?  Why is the sand the color that it is?  How large the grains of sand?  Why? 

For instance, the above sample was photographed (because one should never remove anything from a national park) at Acadia National Park.  You immediately notice, with the naked eye, that the sand is very coarse.  You'll notice that many of the pieces of sand look like crushed shells - for good reason, that's exactly what they are!  You'll also notice lots of different colors in the sand. 

I'm particularly fond of the blues, purples and greens.  The blue and purple pieces are crushed mussel shells.  The green "spikes" are bristles from a sea urchin. 


Along the same lines, retired science teacher Charles Lindgren has created the Science of Sand website.  He has solicited sand samples from across the country and world and photographed the sand at a 9X magnification. 

His samples are organized by state and country, and you're welcome to use the images for a virtual sand lab.  In fact, he's also included some lesson ideas. 

He's also always looking for new samples, so if you live or travel near sand, consider collecting a sample for him. 

And take a look at his site - the pictures are gorgeous, much better than mine!

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.