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Thinking of the lovely spring colors, the pastel blues, lavenders, yellows and pinks? Why not try a few really fun experiments creating and changing colors using chemistry?

The first experiment requires some fresh red, blue or purple flowers (purple petunias work really well); a jar big enough to hold a few flowers with a lid; some twist ties, string or yarn to suspend the flowers; household ammonia; and for the optional last part, vinegar (any kind). The ammonia is pretty strong, so this will require help from an adult.

Have an adult pour about 1/2-inch ammonia into the bottom of the jar. Wrap a twist tie or yarn around the stems of the flowers, enough that will fit comfortably into the jar. Suspend the flowers upside-down into the jar so that they are close to, but not touching the ammonia, by wrapping the yarn or twist tie over the lip of the jar. Put the lid on the jar as much as you can. Wait about 15 minutes and you should see the flowers start to change color.

This part of the experiment is based on one by Robert Krampf in his excellent Experiment of the Week series, although I couldn't find it in his archives. Edit: Robert Krampf has revamped his site, and so this link is no longer valid. Check out the fun stuff he has to offer at the Happy Scientist.

Now comes my addition: once the flowers have changed color nicely in the ammonia (which is a base) then try to change the color back by dipping the flowers in a bowl of vinegar (an acid). Using purple petunias, I was able to turn them a bright teal blue in the ammonia, and then back to purple in the vinegar. You can actually dip them into the vinegar, because it won't bleach. It you dip the flowers into the ammonia, however, it may bleach or discolor them. That is why they need to be suspended in the fumes instead.

The second experiment is the classic use of red cabbage as a pH indicator. If you haven't done this, it really is fun. All you need is red cabbage from the grocery store, a blender (ask for an adult's help), glasses or plastic cups and items to mix with the red cabbage solution, such as lemon juice, soda, vinegar, baking soda, dish detergent and laundry detergent.

Some recipes call for boiling the cabbage (smelly!), but I just ground up the fresh red cabbage in small batches with just enough water to allow the blender to work properly. Pour the batches together in a pitcher (which can be placed in the refrigerator for use later in the day if necessary.) Pour about 1/3 cup of the red cabbage juice into testing containers such as clear glasses or plastic cups. Then mix in about a Tablespoon of one of the testing compounds. Does the color change? Try another material in the next glass. Does the color change more if you add more test material? What happens if you mix two materials, like vinegar and laundry detergent? Have fun admiring the wild colors you can make.

What is happening? The pigment molecules in the red cabbage change shape, and thus color, when in the presence of acids versus bases. Lemon juice, vinegar and soda are acids; detergents and soaps are bases.

For the grand finale, create more wild colors with markers. Fold up a diaper wipe that contains alcohol and tie in bunches with rubber bands. Color with Sharpie-type markers. Allow it to set a few minutes and then unfold to reveal a rainbow of colors in a cool tie-dye pattern. Experiment with more wipes to see what you can create. Note: allow to dry suspended on a line so the dye doesn't move onto other surfaces.

If you don't have diaper wipes, then try white fabric. Tie with rubber bands, if desired and then color with markers. Drop or dribble on some rubbing alcohol and the colors should separate and move through the fabric. Once again, keep on a line or suspended until dry. Once you have the technique refined, you might want to create your own tie-dye T-shirts or socks.

Spring colors rock!


What an odd-looking creature I found on my desert milkweed flower this week. It is bright orange with striped legs. Look at the black spines on back end (abdomen). It also seems to have its straw-like beak piercing a black insect.

This insect is a young assassin bug, a stage called a nymph. If it were an adult, it would have wings.

Assassin bugs use their front legs to capture other insects for food. They stick their proboscis or beak into their victim and suck out the juices. In this case the nymph has caught a tiny parasitic wasp. The wasp was probably searching for aphids, which is what its larvae use for food.

assassin bug nymph

Edit: I was able to find an adult to show in this later post.


Nothing is more fun than a science-based field trip. We went on a field trip on Friday to Arizona State University's Polytechnic Campus. After getting off the bus, our first stop was the Laboratory for Algae Research and Biotechnology, where we met Dr. Milton Sommerfeld, a scientist who studies algae.

You might think algae would be pretty boring. After all, it is that stuff that turns your pool green or grows on the sides of your fish tank, making it hard to see the fish. It is slimy and sometimes really smelly. Who would spend their life studying something like that?

We learned algae is actually exciting stuff and may have a huge impact on our future. In fact, that green goo may soon be golden. It turns out certain kinds of algae contain a lot of natural oils in their cells. The oils can be extracted and turned into a form of biofuel (fuel that comes from recently living things).

Algae have a lot of advantages over other sources of biofuel. First of all they aren't a crop, so making them into fuel does not take food away from people (although one of the by-products of the extraction process is a protein powder that may some day be used for food, too.) The algae can be grown in wastewater from farms high in manure or other forms of water that may not be suitable for drinking. They can be grown in areas that aren't good for farming. And they produce more oil per acre than soybeans.

Of course there are costs too. The algae grow in large tanks, sort of like fish tanks. Electrical pumps are needed to circulate the water in the tanks. Dr. Sommerfeld's group is looking into a way to produce the electricity using solar panels. Extracting the oil also requires some energy, but as the techniques are modified and perfected the process will likely become more efficient.

After visiting the laboratory and seeing all the tanks full of brightly colored algae, it is not hard to imagine cars, trucks and planes running on biofuel in the near future.

For more information, see this recent article from Arizona State University's Research Magazine.

September update: Check for more recent post and link to newspaper article.