End of School: Surivivor Science

This week, I'm going to deviate a bit from my normal science activities and share some ideas for filling in that last week or two of school.  You know, those weeks when you're still responsible for educating your students, but they are so far done with being educated. 

ETA: As I'm putting together this series of posts, I've been looking up the original sources for some of my favorite end-of-the-school-year science activities and I'm noticing a common theme: The Science Spot.  I didn't set out to highlight everything Tracy's done - I just wanted to share things that have worked for me.  That so many of them come from the same spot is a testament to Tracy's great ideas and her willingness to share freely with everyone.  If you haven't already, please go explore The Science Spot. 

The first series of activities I want to share with you is Survivor Science, from The Science Spot. 

I found this to be a wonderful collection of activities that keep my students reviewing science concepts, and a brilliant theme that inspires competition and thus motivates the students to participate. 

There are very few supplies needed - perfect, as no one wants to be getting out all kinds of things while they're trying to pack up their classroom for the summer. 

I found that it could be very flexible, which was of great importance to me.  The last week or two of school were marked with crazy schedules, such that I rarely saw every class every day.  I scheduled the Survivor Science challenges in my plan book and then whichever classes I saw on a given day completed that day's challenge.  The other classes missed out on that challenge, but had their chances with other challenges.  All of my classes were participating, but I didn't have to worry about which class was on which challenge.  They weren't competing amongst classes, just amongst the teams within their own class, so it made no difference if one class had completed more challenges than another.

Summer's Coming....

Sooner for some of you, later for others of you.  But, even if you've still got a good 6 weeks of school left, I know thoughts of long summer days are starting to dance around your brain, even if it does still feel like winter....

Along those lines, I've been debating how to approach the blog throughout the summer.  Last summer I continued posting 5 days per week, but am considering changing things up for a bit this summer. 

If you read this blog on the actual website, you'll notice a new poll on the left side bar.  I'm seeking some input about your anticipated summer readership.  Do you think you'll:

• Read the blog faithfully every day.
• Check in and catch up on the blog ~once a week.
• Ignore the blog all summer but catch up on everything come August.
• Ignore the blog all summer.

 If you read the blog in a reader, or get it via email, I'd appreciate your taking a moment to visit the website and casting your vote. 


And next week, look for some ideas to engage your students during that last week or so of school.

Acid/Base Chemistry: The Cabbage Caper

Still have some red cabbage juice indicator in the freezer?  Pull it out for this fantastic investigative lesson, utilizing knowledge of acid/base indicators. 

The story begins....

Click here for the full story, with all the suspect information. 

When you've read the full story, you'll learn that each of the suspects was using a particular solution.  The students test each of those solutions with red cabbage juice and with turmeric (found in the spice section of the grocery store) to determine which solution, and therefore which suspect, was responsible for the green and orange stains and the murder of Mr. Worthington. 

The suspects' solutions:

• Water
• Salt Water
• Battery Acid (you can use any kind of weak acid)
• Lemon Juice
• Vinegar
• Lye (baking soda dissolved in water will serve the purposes of the lab)
• Ammonia Water (you could use window cleaner)

If you have spot plates, students could set up their tests in one of those - put each suspect's solution in two wells, then add a few drops of cabbage juice to one of those wells and a few grains of turmeric to the other.  If not, use test tubes or small beakers, just make sure to wash them well between each test (you wouldn't want an innocent person to be accused of murder!). 

To conclude the lab, have students summarize the tests they performed and the results of their tests in a statement for the court.

One more note, the color change in turmeric is subtle - it remains yellow in an acid but turns orange in a base.

Today, homicide division has asked you, a reputable chemist, to personally accompany Detectives Sippowicz and Martinex on a murder case. Mr. Robert Worthington, a prominent citizen of our fine community, has been murdered.

On the way to the Worthington mansion, you learn that Mr. Worthington was stabbed, in his own kitchen, with his own carving knife. The maid, according to the police report, had found the cook standing over the body. The police officer on the scene had, therefore, arrested the cook on suspicion of murder. The cook, being a good friend of Sippowicz, had immediately called him, seeking his help. Sippowicz claims that the cook could not have done it since Mr. Worthington paid his cook more than any other employer in the city. His death will mean a substantial reduction in the cook’s salary, he claims. Besides, she is a very gentle person. She would never even raise a hand to kill a fly.

When you arrive on the scene, Mr. Worthington is still lying on the kitchen floor with the carving knife still protruding from his chest. As you examine the knife, you notice a STRANGE GREEN STAIN on the handle. Nearby are some ODD ORANGE STAINS. These are unusual because they are not blood stains. Fingerprints are covered up by the stains, making them unavailable for evidence. As Martinez questions the cook, you and Sippowicz set out to question the rest of the staff. One hour later, you, Martinez and Sippowicz meet to discuss the suspects.

Know a Great (Science) Teacher?

Rayovac is sponsoring 3 all-expense paid trips to Steve Spangler's 3 day Science In the Rockies, in Denver, Colorado. 

Head over here to nominate a K-6 teacher you know and love (self-nominations are accepted).  Any and every science teacher I know would absolutely love to win this trip.  Steve Spangler's workshops are held in high regard, and who could resist a few days in Denver?  Plus, every participant heads home with $300 worth of Steve Spangler goodies.  Nominations need to be made by May 16, so don't wait to too long. 

Of course, if you're interested in attending, you can pay your own way and sign up here.  When my lottery winnings come in*, I'm so there!  In the meantime, I've got a few people to go nominate. 

*wait... what... I have to buy a ticket in order to win the lottery.... hmmm... time for plan b...

Osmosis: Should I Salt My French Fries Before or After Cooking?

Cut a potato into 4 sticks, about 1/2 cm thick (5 mm or about 1/4 inch).  You could try other shapes as well.

Fill two beakers or small bowls with water.

Dissolve salt in one of the beakers of water, about 1 tablespoon per cup of water.

Place 2 potato slicks in each beaker and allow to sit for about an hour (you can leave it overnight if need be).

After the time has elapsed, pick up the potato slices and observe.

You should find that the potato slices that were in water are limp and bend easily, which the ones in pure water are still rigid and crisp. 

Through osmosis, water moved out of the potato and into the salt water. 

Weather: How Much Air is Pushing on You?

The air all around you is filled with molecules, all of which exert pressure on you. 

Picture this...
You're standing upright.  Rising straight up from your head, into the furthest reaches of the atmosphere, is a column.  This column is filled with air molecules.  While the effect of each individual molecule is miniscule, their combined effect is a force with which to be reckoned.  How much atmospheric weight do you think your head has to support?  Go ahead, take a guess...

First we need to find out how large your head is.  For the purposes of this activity, we're going use inches so we can get an answer in pounds.  It's rather un-scientific of us, but it will provide us (in the U.S.) with the greatest understanding.

Back to your head.... find the circumference of your head, using either a fabric measuring tape or a length of string that you then lay against a meter stick.  I come up with 22 inches.

Now you'll need to do some math to find the radius.  Circumference is equal to 2 x pi x radius.  So, to get the radius, you'll need to divide the circumference by pi and then divide that number by 2.  For me, it's 3.5 inches.

Now you'll use the radius to find the area of the top of your head.  Area is equal to pi x radius x radius.  For me it's 38.47 square inches. 

Atmospheric pressure at sea level is 14.7 psi (that's pounds per square inch), and while I don't live exactly at sea level, that number will work well enough for our purposes.  So, the area of my head multiplied by atmospheric pressure gives me the weight of air pushing on my head.  In my case, it's 38.47 square inches x 14.7 psi = 565 pounds. 

Pretty unbelievable, isn't it?  But it's true.  We aren't aware of it because we're used to it, we've never known anything different.  And we aren't crushed by that force because there are fluids inside our body exerting pressure that keeps things balanced.  Those air molecules are pushing on all sides of your body, not just on top of your head, which also helps keep things balanced.

If you're interested, atmospheric pressure in Denver, with an approximate altitude of 1 mile, is 12.2 psi.  You might want to have your students determine how much the atmospheric weight changes as they go from sea level to 1 mile.

Density: The Sugar Density Column

Did you know that you can change the density of water by adding sugar to it?  Did you know that you can actually create layers of sugar water that have different densities? 

I've seen the Flinn Version, How Sweet It Is, numerous times, and it's very cool. Unfortunately, it's not very practical for me.  I'm not in a classroom, so I don't have balances readily available, nor do I have access to ring stands and separatory funnels.  I've always figured I could find a way to recreate the experiment to make it work for me, but I've just never made it that far down my list of things to do.

And then I found this version, which does not require any of the aforementioned equipment.  (I have adapted it slightly to include two additional colors).  And, if you're just planning to make the solutions ahead for demonstration purposes, it's faster.  In fact it's perfect for doing at home.  It's also simple enough for young students to help with. 

Now, before I go on to show you how simple it is, let me point out that for older students the Flinn version may be superior:
1 - It's always good to practice using equipment to make accurate measurements.
2 - In the Flinn version, students find the mass of the sugar, which allows them to calculate the actual density of each solution.  You could also have them calculate the sugar concentrations.

Enough talking, on with the fun!

Line up 5 glasses.  Add sugar to the glasses as follows:

Glass 1: no sugar
Glass 2: 1 tablespoon
Glass 3: 2 tablespoons
Glass 4: 3 tablespoons
Glass 5: 4 tablespoons
Glass 6: 5 tablespoons

Add 4 tablespoons of water to each glass and stir to dissolve the sugar.  Make sure the sugar in each glass is completely dissolved.  If you need to add water to one glass, you'll need to add an equal amount of water to each of the other glasses.

Add food coloring to the glasses, a total of 2-3 drops per glass, as follows:

Glass 1: red
Glass 2: red + yellow
Glass 3: yellow
Glass 4: green
Glass 5: blue
Glass 6: blue + red

To make the column:

Pour the purple solution into a tall, colorless glass (or a graduated cylinder if you have one). 

Hold a spoon over the glass, near the top of the purple solution, and pour the blue solution slowly over the back of the spoon.  This technique will minimize the mixing of solutions.

Using the same technique, add the remaining solutions in the following order: green, yellow, orange and red.

As you can see, I haven't yet perfected the pouring technique, but it isn't completely muddled either.  I think I could have gotten a better rainbow if I had tried again immediately after doing this one, but I decided it wasn't worth using a bunch more sugar just to capture a better photo.  That said, I think my rainbow looked better than the above photo shows - I just couldn't get the light right to show all the colors. 

If you're doing this as a demonstration, you very well may want to make sure you have enough solutions to give yourself a test run before the actual assembly.