Plasma Experiments on "Integrated Science"

We've been doing some amazing plasma experiments over on our current blog, Integrated Science at Home. If you haven't visited, come take a look!

Homemade Lava Lamp -- New and Improved!

We recently tried a new and improved version of the lava lamp project from several years ago. It worked great! Here's how we did it:

Tools and Materials:
• Clean recycled soda or water bottle, label removed, 16 oz or larger
• Water
• Food coloring
• Baby oil, at least one 12 oz bottle
• Effervescent antacid tablets (such as Alka-Seltzer)
• LED push light (or make a light-up base from a recycled jar or can, some extra bright LED bulbs, coin batteries, and tape)
• Plastic plate or other protection for table
• Cooking (meat) thermometer (optional)

Step 1: Prepare the lava lamp bottle. The first step in building your homemade lava lamp is to find a tall, thin, clear bottle. Any size or shape will do. A plastic bottle, such as a recycled soda or mineral water bottle, will eliminate worries about breakage if it falls. We used a 16-ounce bottle, which is large enough to get the full floating blob effect, but only requires one 12-ounce bottle of baby oil. A larger lamp bottle will last longer but you’ll need more baby oil to fill it. Rinse the bottle clean and remove any labels. A glue solvent like “Goo Gone” can make scraping off a tough label easier.

Step 2: Prepare the Bottom Layer of Colored Water.
Once you’ve got your bottle ready you can begin filling it. The exact chemical formula used to make real lava lamps is a trade secret (although the UK manufacturer Mathmos has a cool video on its website showing the lamp being assembled). But as with the egg timer which inspired it, the gooey “lava” is actually a type of wax. And the way it slowly floats up and drifts down has to do with the balance between the density of the wax and the density of the liquid it floats in.

Density tells us how much of a substance is contained within a certain volume, or amount of three-dimensional space. The higher the density, the more stuff is in there. And density can change with temperature. For instance, at room temperature the wax in a lava lamp is denser than the liquid, so it sits at the bottom of the lamp. When the light is turned on and the wax warms up, it begins to melt and spread. As the volume of wax in the lamp grows, its density decreases, because the same number of molecules are now taking up more space. At the point where the wax becomes less dense than the liquid, it starts to float to the top of the lamp. Eventually the wax at the top, away from the hot light, starts to cool. As it becomes denser, the wax sinks down, is warmed by the light, and the cycle repeats itself in a colorful mesmerizing display.

Our homemade version uses water and oil, but the principle is the same. Oil is less dense than water, so the water in our lamp sinks to the bottom, while the oil floats to the top. When we introduce a less dense gas into the water, bubbles form that carry some of the water slowly up through the oil. By coloring the water with dye, we can approximate a lava lamp-type effect that lasts several minutes.

If spilling food coloring or oil is a concern, place your bottle on a plastic plate or other protected surface. (They can also stain clothing, so old clothes or an apron may be advisable.) Fill the bottle about one quarter full with water. Add 3 to 4 drops of liquid food coloring for a 16-ounce bottle, or more for a larger bottle.

Before you shake up the bottle to mix the food coloring, take a few moments to watch as the dye begin to spread in vibrant tendrils of color, all on its own. That seemingly spontaneous, random movement is called Brownian motion, after the botanist Robert Brown. In 1827, Brown looked at grains of plant pollen in a drop of water through a microscope and noticed that they jiggled around. In 1905, Einstein suggested that the pollen grains were moving because they were colliding with molecules of water, and predicted that the way the grains moved could be used to figure out how many molecules of water there were. Scientists later showed that Einstein’s prediction was correct -- one of the first proofs of the existence of atoms and molecules.

Once you’ve mixed up the food coloring and water as evenly as possible, by shaking, stirring, or just letting Brownian motion do its thing, check to see if you need to add any more dye. To get the lava lamp effect to work, you want the water to look pretty dark. But don’t go overboard at this point. If necessary, you can add more food coloring later on in the process.

Step 2: Add the Top Layer of Oil.
Now that you’ve got your colored “lava” layer ready, it’s time to add the clear liquid. We use baby oil, which is colorless and available pretty much anywhere. Baby oil is mostly mineral oil -- a non-toxic byproduct of the manufacture of gasoline, used to lubricate cooking tools and to make gummy candy -- with a little fragrance added to make it smell nice. Compared to cooking oil, baby oil is also inexpensive. I picked up a 12-ounce-size bottle, enough for one 16-ounce homemade lava lamp, at my local dollar store. Of course, you can use any kind of cooking or skin care oil you have on hand, as long as it’s not too dark to see through.

Pour the oil into the lava lamp bottle slowly, stopping when you reach the bottle’s shoulder. You’ll want to leave a little head room so the lamp solution doesn’t bubble over. Let the bottle sit for a minute or two, so that the contents settle into two layers: colored water on the bottom, oil on top, with a nice sharp line in between.

Here’s where density comes in. As already mentioned, oil is less dense than water, so the same volume of oil weighs less than an equal volume of water. In scientific terms, the specific gravity of mineral oil – or the ratio of its density compared to the density of water – is about 0.8 to 1. However, there’s another reason that oil and water form two neat layers, and it has to do with the bonds that make molecules stick together with other molecules.

If you could see a water molecule, you’d notice two little hydrogen atoms sitting on top of a bigger oxygen atom like the ears on Mickey Mouse’s head. Those “ears,” which each have negatively-charged electrons whirring around them, give that end of the water molecule a slightly negative charge. That makes water a type of polar molecule. Just like magnets, the negative end of polar molecules is attracted to the positive end of other polar molecules. Oil molecules, on the other hand, are non-polar. They’re made up of long chains of carbon and hydrogen atoms, which don’t have a charged side. Non-polar molecules will form bonds with other kinds of non-polar molecules (“like dissolves like”), but when put together with polar molecules, they keep to themselves. So when people say “oil and water don’t mix,” what they’re really talking about is molecular polarity!

Step 3: Set up the lights.
So far you’ve built what science teachers call a density column – one type of substance floating on another. To turn it into a lamp, you need to add a base with a light source. A small battery-powered LED push light is ideal. These look like discs with three or four LED bulbs embedded in them. You can find inexpensive versions in the flashlight section of your local dollar store or discount mart. Just set the LED push light on your plate or protected surface, and carefully place your lava lamp bottle on top so that the liquid inside is lit up.

If you can’t find one of these handy lights, you’ll have to make your own base. A large sturdy plastic jar or a can should work fine. Arrange some new or re-used LED bulbs inside. To power them, slip a button battery between the wires of each LED bulb and tape in place.

Step 4: Start the action!
Unlike real lava lamps, which run on the heat of a light bulb, our homemade lava lamp is powered by the energy released when you drop an effervescent (fizzing) antacid tablet like Alka-Seltzer into water. You’ll probably have to break the tablet in half to fit it in the opening of the bottle, but try to use as large a piece as possible. The bigger the piece, the more dramatic the effect!

As the tablet hits the layer of water at the bottom of the homemade lava lamp, it begins to release bubbles of gas. Because gases have a lower density than liquids, the bubbles float slowly upward through the thick layer of oil, carrying drops and blobs of water along with them. But when the bubbles reach the surface, the gas continues rising, while the denser water that’s left behind drifts back down to the bottom of the lamp. The lava lamp effect will continue as long as the tablets are fizzing. You can keep adding pieces of antacid tablets to prolong the show, until the oil gets too cloudy to see through.

What’s happening when the tablet begins to fizz is actually the same chemical reaction as the classic baking soda-and-vinegar volcano. Fizzing tablets contain an acid (powdered citric acid, which gives lemon juice its sour taste) and a base (sodium bicarbonate, our old friend baking soda). Acids are compounds with an excess of hydrogen (H+) ions, or hydrogen atoms that are missing their electron and have a positive charge. Bases have a surplus of hydroxide (OH-) ions, which are negatively-charged molecules of oxygen and hydrogen. Strong acids and bases are highly reactive – they’ll combine with, and start to dissolve, many types of material, including your clothing and skin. But put them together in the right amounts and they’ll neutralize each other to produce water! (H+ and OH- make H2O.) When fizzing tablets react, they also produce a salt (in this case, sodium citrate) and carbon dioxide (the gassy bubbles).

Know what else is cool? The reaction of fizzing tablets and water creates an endothermic reaction. That means that those chemical changes are pulling heat out of the surrounding water to use as fuel. So as it’s fizzing, your lamp is dropping in temperature. Try sticking a cooking thermometer in your bottle to see if you can detect the change in temperature. (You might want to skip the lights, since they may give off a small amount of heat energy.)

Flower Chemistry

Over at GeekMom, we've gotten some great responses to Mythbuster Kari Byron's post about getting kids excited by science. One commenter, who only gave the name "OrchidGrowinMan," provided directions for a flower chemistry party he organized for his daughters. It sounds so interesting, I thought I'd share it here. Maybe we'll get to try it sometime ourselves.

Years ago, I hosted a “Science Party” for my eight-year-old daughter to test flowers from our garden for acid/base color indicators. Ten of her friends came over, and spent HOURS at it, skipped lunch (!) and some had to be dragged away. The agenda was to gather flowers and such from the gardens and greenhouse (orchids too!) and smoosh them in a mortar and pestle with a bit of rubbing-alcohol (When I was a teenager, I experimented and found this to be the BEST solvent for this purpose). Then a dropper could suck-up the (usually) colored solution to put a few drops into each of three tubes, adding acid to one, water to one, and alkali to the third. I had bought each of them a set of safety goggles, plastic droppers and a rack of 25 little plastic test-tubes to take home (surplus).

Some surprises came up, like the prevalence of flavonoids that turn yellow with strong alkalis (so some samples go red-purple-blue-green with increasing pH). They're the reason why when you wash your hands after handling tomato plants the soap turns yellow: You can easily collect lots of some weird pigment by stroking tomato stems with a cotton-ball, and it turns bright greenish-yellow in alkali.


Materials were obtained from American Science & Surplus at good prices:
American Science & Surplus
3605 Howard street,
Skokie IL 60076
(847) 982-0870
http://www.sciplus.com/

List of Materials

• Safety Goggles  $2.25 ea.
• Test Tubes (at least five)  $1.75 ea.
• Test Tube Rack
• Mortar and Pestle  $13.95 ea.
• Droppers Provided  $2.00/20.
• Acid: distilled vinegar, lemon juice
• Alkali: household ammonia, baking soda
• Solvent: rubbing alcohol
• Apron or Lab Coat Recommended
• Pigmented plant parts: flowers, berries, pods.
• Acidic foods like fruits, alkaline like soda- or shortbread or cake.
• Miscellaneous, if available and needed: Ph Meter, Litmus paper, Acid/base indicators, tincture of iodine

What Will We Do:
1. We will do experiments to try to extract the colours from plant parts like flowers, leaves and fruits.
2. We will then determine if these chemicals change colour when they are mixed with acids and alkalis. That is, are they acid/base indicators.
3. Using any acid/base indicators we find, we will try to identify whether some foods are acidic or alkaline (basic).

Procedures (The three experiments can be run concurrently):

Experiment 1

1. Obtain a pigmented plant part, the darker the better. The dryer the better. If possible, cut away any uncoloured parts.
2. Smoosh and Goosh it up in a mortar and pestle.
3. Add a little rubbing alcohol and carefully grind it up some more.
4. Pour, or use a dropper to remove the liquid to a test tube. Label the tube. What does it look like?
5. Wash the mortar and pestle and repeat.

Experiment 2

1. Put a few drops of the extracted pigment from experiment 1 into each of five test tubes.
2. Put three drops of ammonia or baking soda solution in the left test tube. What happens?
3. Put three drops of vinegar or lemon juice solution in the right test tube. What happens?
4. Put one drop of ammonia or baking soda solution in the next to left test tube, and two drops of water. What happens?
5. Put one drop of vinegar or lemon juice solution in the next to right test tube, and two drops of water. What happens?
6. Put three drops of water in the center test tube. Compare the colors of each sample.
7. Put a few drops of the extracted pigment from experiment 1, one that changes colours, into each of five test tubes.
8. Put three drops of ammonia solution in the left one, three drops of baking soda solution in the next. What happens?
9. Put three drops of vinegar in the right one and three of lemon juice solution in the next. What happens?
10. Put three drops of water in the middle tube. Compare the colours.
11. Using the results of the experiment above, if you add a drop of vinegar to the left (ammonia) tube and a drop of water to the middle one, and a drop of ammonia to the right (vinegar) tube, how many times do you have to repeat to get them the same colour?

Experiment 3

1. Obtain a food (or other material) sample.
2. Put a few drops of the extracted pigment from experiment 1, one that is shown to be an indicator, onto the sample. What happens. Is the sample acidic or alkaline?

Why Does That Happen?
The pigments in plants fall into one of several chemical families. Blue, purple, pink, and most red colours are due to the presence of one or another of the anthocyanin pigments, which are acid/base indicators. [antho means “flower,” cyanin means “blue.”] Their molecular shape changes in response to acidity, and this changes their colour. Some blue flowers have the same anthocyanin pigment as some pink ones; the difference is in the acidity/alkalinity (pH) of the plant juice. Vinegar and lemon juice are acidic, ammonia and baking soda alkaline. Float flowers in them and the flowers will likely change colour.
Anthocyanins are soluble in water and alcohol and are easy to extract, They also are usually easily destroyed by heat (cooking). Beets and chard (and cacti) have pigments in a different group, betacyanins, which are more heat stable and are also (barely) indicators. [Beta means “beet.”]
Yellow, orange and some red pigments (as in tomatoes) are due to carotenoid pigments, which are not acid/base indicators, and are not really soluble in water and sparingly in alcohol. [carota means “carrot”] Green chlorophyll and various brownish pigments may also be present.

There are other experiments that can be done: baking soda combined with an acid makes bubbles (carbon dioxide), tincture of iodine from the medicine cabinet gives a black/blue colour on starch and can be used to detect starchy foods and where in a plant starch is stored.

Now Blogging at GeekMom with Mythbuster Kari Byron!

I've been busy the past few months helping to launch GeekMom, a site dedicated to moms who want to share their geeky passions with their kids. To start us off, we've got MythBusters host Kari Byron writing about her new adventure as mom to a one-year-old girl. Kari is also the host of the new hour-long kids' show Head Rush. Check us out!

And I'll still be blogging at GeekDad, so be sure to stop by there too!

The Buckyball is 25 today!

Google's animated doodle alerted me to this milestone in modern chemistry. Buckyballs, discovered in 1985, are carbon molecules that are exceptionally strong and light. They're used in carbon fiber bike frames and a whole host of other cutting edge products. We saw the original inspiration, Bucky Fuller's geodesic dome, on a trip to Montreal.

Check out my post on GeekDad.

Discover Magazine is Looking for Home Experiment Videos!

Unfortunately, all our best videos are just a couple seconds long. But if you're interested:

DISCOVER is currently producing a Web TV show about home science experiments and demonstrations, and we're looking for submissions—the most enlightening, visually impressive, surprising, or just plain funny videos out there. Submit your video below (it's OK if you've already uploaded it elsewhere on the Web) and we'll select the best ones for the show. (Winners will of course be identified.)

For more information, go to the Discover Magazine website.

Lots of Periodic Tables

Just a pointer post to an interesting post by my fellow GeekDad writer Nathan Barry on some creative versions of Periodic Tables, including illustrator Russell Walks' cool-looking Periodic Table of Imaginary Elements.