Science Club: Forensics

As an avid fan of Forensic Files, I can assure you that I think forensic science is fascinating. As such, I figured it would be a fun idea to bring a little bit of it into science club. Specifically, we're concentrating on ink chromatography and fingerprints today.

Chromatography

Chromatography is the separation of a material (in this case, ink) into its component parts (in this case, the colors that make up the ink) by using a solution in which it dissolves (such as rubbing alcohol) on a medium in which different colors move at different rates (here, a coffee filter).

Basically: Different brands of pen will use different types of ink, which are all *slightly* different shades of blue. Perhaps one pen is a little more green, and another is a bit more purple, but it's hard to tell by looking right at the ink. What to do? Separate the ink into its component colors! Every pen will have a different pattern, and you'll be able to see which pen wrote the note.

The Story

I started by telling a very sad story: SOMEONE has stolen Miss Kat's chocolate! They left a note saying, "sorry!" but didn't sign it. How can we figure out whodunnit?

Well, I just so happen to have collected the favorite pen of three of my coworkers. I've already used chromatography to analyze the ink in the note - now we have to analyze the ink in the pens to see which pen wrote the note (and therefore which person ate my chocolate). 

You Will Need

• At least 3 pens of the same color, in different brands (I used blue pens, because it was easier to see the color differences in blue than black ink)
• Coffee filters
• Rubbing alcohol
• Clear plastic cups
• Pencils and small binder clips

Setting Up

Step 3: My guilty party.

1. Cut the coffee filters into rectangles, roughly 1" wide and 3" long. You will need 3 rectangles per participants, plus extras in case anyone messes up.

2. Label the pens, so we can keep track of which pen makes which mark. I labeled mine with the names of coworkers (with their consent), but using A, B, and C, or 1, 2, and 3 would work just fine. 

3. Use chromatography to separate out the ink of one of the pens, as described below. This is your guilty party, which the scientists will all try to match the suspects' pens to.

Chromatography

Each participant gets one lab report, three coffee filter rectangles, three binder clips, a pencil, and a plastic cup.

Take turns using the pens to write on the coffee filters; at the top of each, write the suspect's name. About 1/2" from the bottom of the filter, draw a thick horizontal line (or, scribble with pen enough that it looks like one solid line). 

Clip one binder clip to the top of each rectangle, and thread all three clips through the pencil. Add about 1/2" of rubbing alcohol to your plastic cup, and suspend your pencil and its test rectangles over the cup. The bottoms of the rectangles should reach the liquid, but the ink line should be above the liquid's surface.

Wait and watch in wonder as the ink starts to separate. It may take a good 15 minutes before your samples are done, so this is a good time to start on fingerprinting. (Of course, it starts right away, so sometimes it's hard to stop watching it...)

See that teal stripe at the bottom?
It was LAURA who stole my chocolate!

Once the ink has stopped separating, you can carefully remove the rectangles from the cup, and examine them to see which pen wrote the note - and therefore which coworker stole the chocolate.

NOTE: If you don't want to use rubbing alcohol, this experiment can be done with washable markers and water.

Fingerprinting

I had originally intended to use an ink pad for fingerprinting, but that can be messy, and there's an easier way.

What You Need

• Pencils
• 2 pieces of paper per participant
• Clear tape

What to Do

1. Using your pencil, make a large dark mark on your paper. 
2. When you have plenty of graphite on the paper, rub your finger in the spot until it's covered. 
3. Then, press the sticky side of a piece of clear tape to your finger and press down. 
4. Remove the tape and stick it to a piece of clean paper (or, in this case, the lab report). 
5. Repeat for all fingers.

Then, take a look at all the whorls, arches, and loops that your fingerprints have. Do any of yours match? Do they match anyone else at the table? They shouldn't! It's a one in a million chance that someone has even one fingerprint the same as you do. 

Lab Report

Here's the lab report I made up for Chromatography and Fingerprinting. I actually taped my Guilty sample to the "The Culprit" section of the paper and color-photocopied it before we began.

Soda Can Science

My science club has hit a bit of a plateau. I only get 3 to 5 kids, and their ages are so varied that it's hard to find something that interests all of them. I read somewhere in my travels that diet soda floats, while regular soda sinks (Really!!), so I designed this density experiment to celebrate the awesomeness of this fact. 

This week, I only had three kids for Science Club  - but they were all of similar age, and they all had a fantastic time. Plus, it was easy!

What You Need

• A large clear plastic tub mostly filled with water
• 6 cans of soda - a mix of regular and diet (please note: this doesn't work with mini cans)
• Canister of salt
• 2 plastic cups
• Kitchen scale
• Something to stir with (we used a ruler)
• About 20 sugar packets
• About 20 artificial sugar packets
• Orange (nice but not required)
• Aluminum foil (optional)
• Willing kids to participate (hereafter referred to as your scientists)

What To Do

The Optional Part
Place the tub of water on a table so everyone can see. Shape your aluminum foil into a little boat. "Will this float, or sink?" Your scientists will all agree that it floats. Demonstrate.

Crumple the foil into a ball. "Will it float now, or sink?" (Please note: you need to crumple it REALLY WELL, or it will continue to float, and you will look silly.) The scientists usually agree that it will sink - if you did it right, it will. So, what changed? The density changed, which is a measure of how much something weighs compared to how much room it takes up. 

"Will the orange sink or float?" You may get differing answers on this one but the orange should, in fact, float. Neat. What if we peeled it? Your scientists will probably agree that it will still float, but they will be surprised to see it sink! Why? Because the orange peel has so much air in it, it acts as a flotation device, like if you wore a life jacket when you went swimming. So what does it mean if it doesn't have as much air in it? The orange without the peel is more dense. (You see where I'm going with this.)

The Rest Of It
SO! Will a can of soda float, or sink? Drop the cans in one at a time, starting with a regular (non-diet) soda. It will sink. ("Duh," I was told.) Then, try a diet can. It... floats? WHAAAAAAT? Continue with all of your cans. 

What's the difference between the cans that sink and the cans that float? The ones that float are DIET sodas. So what's the difference between a regular soda and a diet soda? Fish out all the cans and take a look. (You can put your tub of water aside now, if you have room.)

The sodas all have the same amount of liquid in them - that's the volume. Put them on the scale one by one and notice that the diet sodas weigh less than regular sodas. This means that the regular sodas are more dense than the diet ones.

This is 16 packets of sugar.

But why? Well, take a look at the sugar content of the sodas. The regular soda cans that I had each had 49 grams of sugar (!) while the diet ones have sugar substitutes in them.

Put an empty plastic cup on your scale and zero out the weight. Ask the scientists to add enough sugar to make 49 grams, and count how many packets of sugar that takes. (Our count was 16 packets. SIXTEEN PACKETS, in one can of soda!)

Put a new cup on the scale and zero it out. Now, take 16 packets of artificial sugar and see how much that weighs (about 16 grams). Allow the kids to feel the difference in the weight of the cups, and also the weight of unopened packets. Wow, so that's why it's such a difference in weight, and therefore in density!

If you have moved your water tub, it's time to bring it back. Ask if anyone has any ideas on how to make all the soda cans float. (Mine didn't, aside from pouring out the cans.) "Well, we can't change the density of the cans, but we can change the density of the water." Bring out a container of salt and allow the scientists to pour it (all of it!) in, and stir (we used a ruler for this) until it was as dissolved as possible. 

We put the cans back in and noticed that the diet ones bobbed at the surface even more than before. The cans on the bottom sank more slowly than before, but when one of our scientists started stirring the "soda soup," we noticed that the cans moved when the water moved - it was hard to see, but they were, in fact, floating. Magic? No! Science!

Kat's Note: because of the sugar content of ginger ale, which is less than most cola, orange soda, and grape soda, ginger ale will float, but not as high in the water as diet soda. Maybe skip the ginger ale.

Lab Report

I made this lab report with Canva. I have it in PDF form; just shoot me an email if that works better for you. Otherwise, right click and save these images and paste into a Word document to print.

Science Club - Lego Volcanoes

When I started at the library where I currently work, a few months ago, there was a weekly LEGO-building club. And, okay, I love LEGO, too - but every week? Since it wasn't novel and exciting anymore, and the kids knew they could come whenever they wanted and build, the group had dwindled down from over a dozen to 2 or 3 kids each time. I decided that it was time to shake things up! Now, every Thursday after school, I run Afternoon Explorers, and we rotate between Science, Art, Cooking, and - of course - LEGO. This week was Science, and I decided to appease my LEGO diehards with a fun experiment. Behold, the LEGO volcano! 


The concept is pretty simple - it's a baking soda volcano, but you have the kids build the volcano out of LEGO, around a styrofoam cup. Then, you can let it erupt all over the LEGO, cleaning them in the process. A drop of dish soap makes it more foamy, and a couple drops of food coloring make it even more exciting.

What I Did

I had set up little trays (we had them in the supply closet), each with one styrofoam cup and a couple handfuls of LEGO.  The directions were: Build up the LEGO around the cup, as much as you want, as long as it still fits inside the tray. (For some reason, this was really hard for some of them to understand, but they got it eventually.)

When each kid was done building, I came over and put three spoonfuls (which is WAY TOO MUCH, see below) of baking soda into the styrofoam. Then, the kid came back to my little side table and got a plastic cup, which we filled halfway with vinegar, and added a couple drops of dish soap and a couple drops of whatever color food coloring they wanted.They stirred it with a popsicle stick, poured it into the baking soda, and watched in amazement as their volcano erupted.

This whole project went fairly quickly - one got bored and wanted to see the eruption, and then once we saw one eruption, everyone had to do their own RIGHT THEN. I even had a few kids come in who were way too cool for Science Club, until they heard there were eruptions, and then they had to come do their own. A couple kids did two volcanoes each, which was fine because I had the supplies.

What I Did Wrong

TOO MUCH BAKING SODA. Holy crud. Instead of cleaning the LEGO, my pieces were all coated with a fine, gritty layer of baking soda paste.  Even rinsing them off quickly wasn't enough, so I had to put them all in the big staff room sink with what was left of the vinegar, and some water, and rinse them all off, and leave them to air-dry on a couple old towels. They're fine now, but that was work that didn't need to be done. 

Would I Do It Again?

Yes. With less baking soda.