Stories tagged experiment


Red cabbage juice is a safe, natural, easy-to-make acid/base indicator that allows you to see the carbon dioxide in your breath. The trick is to use a very small volume of cabbage juice, since it's not very sensitive.
CO2 red cabbage experiment
CO2 red cabbage experimentCourtesy Liz Heinecke

You'll need red cabbage, drinking straws, and very small cups (sample cups or the ones for measuring liquid medicine with work well.) Chop a head of red cabbage, cover it with water in a pan, and boil for about 10 minutes. Then, let it cool and collect the juice. The juice will be purple, but it turns blue when exposed to a base or pink when exposed to an acid. Pigments in the cabbage, called flavanoids, change color when they come in contact with acids and bases.

Pour an equal volume- a teaspoon or two (5 to 10 ml)- of the (cooled) juice into each of two small cups. Take a straw, put it all the way against the bottom of one cup and blow through the straw repeatedly for a few minutes until you see the cabbage juice you're blowing into turn noticeably pinker than the juice in the control cup.
red cabbage CO2 test photo 2
red cabbage CO2 test photo 2Courtesy Liz Heinecke

What happens? The carbon dioxide in your breath combines with the water in the cabbage juice to form carbonic acid, which causes the pH of the solution to drop, making the pigment in the cabbage juice turn pink.

Why is this interesting? About a quarter of the carbon dioxide released by activities like burning fossil fuels and burning down rainforests is absorbed by our world's oceans. This results in the ocean water becoming more acidic, like the cabbage juice in the experiment, and can have an effect on sea life, like coral. To learn more about ocean acidification and the chemistry of ocean acidification, check out NOAA's amazing website.

If you have some cabbage juice left over, you can soak white coffee filters in it, dry them and cut them into strips to make litmus paper. It's also fun to pour 1/4 cup of cabbage juice into each of two cups, add a Tbs. baking soda to one cup, 2 Tbs. of vinegar to the other cup and then pour one cup into the other to see lots of carbon dioxide bubbles form as the vinegar (acetic acid) reacts with the baking soda solution (sodium bicarbonate.)


Back when BP was still trying the "top kill" method of slowing the flow of oil into the Gulf of Mexico, the news was full of references to "drilling mud."

Make some oobleck: It won't stop the oil flowing into the Gulf of Mexico, but it's fun, and you'll learn something about non-Newtonian fluids while you're at it.
Make some oobleck: It won't stop the oil flowing into the Gulf of Mexico, but it's fun, and you'll learn something about non-Newtonian fluids while you're at it.Courtesy JoshSchulz

This stuff is no ordinary mud. It helps a rig drill faster and keeps the equipment cool and lubricated, but it's got some wacky other properties. It's a non-Newtonian fluid. That means its viscosity changes as you apply stress. If you punch or hit a shear thickening non-Newtonian fluid, the atoms in the fluid rearrange themselves in such a way that the liquid acts like a solid. A shear thinning non-Newtonian fluid (like ketchup or toothpaste) behaves the opposite way, getting thinner and drippier under stress.

Still don't quite get it? Check this video:

When they're running--applying a stress whenever their feet strike the surface--the fluid acts like a solid and they can walk on top of it. But when he stands still....

The Mythbusters have played with this phenomenon, too:

So. Drilling mud behaves kind of the same way. Here's Bill Nye explaining it all on CNN. When the drilling mud passes through a narrow opening, under pressure, it locks up and acts more like a solid. The idea was that if BP could pump a water-based drilling mud into the ruined well head and get it to solidify, then they could slow the flow of oil enough that engineers could encase the whole thing in cement. It didn't work. That's because the oil and gas spewing out of the pipe are under tremendous pressure. BP engineers just couldn't pump enough mud in there to stop the oil.

Depressing, huh?

But oobleck isn't. What's oobleck? It's a non-Newtonian fluid you can make and play with at home.
Instructables tells you how.

Corn Flake Cereal with Blueberries
Corn Flake Cereal with BlueberriesCourtesy TheBusyBrain
On this date in 1884, Dr. John Harvey Kellogg applied for a patent for "flaked cereal". Kellogg was a health-food fanatic, and was trying to improve the diet of patients at his hospital. His search for a digestible bread-substitute led him to boiling wheat and by accident letting it stand too long and become somewhat hardened. Despite the mistake, Kellogg put the concoction through a rolling process that turned each grain of wheat into a flake, which he then baked into a crispy and light breakfast product. Kellogg's brother Will helped improve the process, began marketing it to the general public, and the rest is cereal history.

Kellogg's Company History Timeline


Not to freak y'all out, but did you know that germs are on everything you touch? Using a special powder called Glo Germ (get it here) you can actually see how germs spread from one thing to another. It will make you want to wash your hands more often. (And the CDC recommends washing your hands frequently. In fact, why don't you go wash up right now?)

Scrub 'em: Use soap and water, and wash for 20 seconds. That's about the time it takes to sing the "Happy Birthday" song twice.
Scrub 'em: Use soap and water, and wash for 20 seconds. That's about the time it takes to sing the "Happy Birthday" song twice.Courtesy mitikusa

Goal: to observe how germs are spread
Age level:: 3 and above
Activity time: 2 - 5 minutes
Prep time: 5 minutes

Materials needed:

  • Glo Germ powder
  • Toys or common household/school/office objects to "spike" with germs
  • UV lamp or detector box


  1. Sprinkle Glo Germ powder on your objects.
  2. Arrange them somewhere where others can handle them.
  3. Plug in UV lamp, but don't turn it on.

Encourage others to pick up and play with the objects. Ask them what they know about germs.

  • Do you know where microbes are found?
  • Do you know what a microbe/germ is?
  • Do you know what illnesses are caused by germs?
  • Do you know the best way to avoid getting sick because of germs?

After the discussion, tell them that, as part of an experiment, you've put "pretend" germs on one or some of the objects they may have touched today. Switch on the UV lamp: what glows?

Reinforce the fat that the Glo Germ powder is just to simulate germs. It won't make you sick. You can get rid of the germs by washing your hands. In fact, encourage your audience to wash their hands and then hold them under the UV light again.

(On the other hand, remember that not all germs are bad. Exposure to some germs is thought to protect people against asthma and allergies or colitis, and overuse of antibacterial products leads to antibiotic resistance and superbugs as well as potential damage to the environment.)


Since the new WATER exhibit is now on display here at the Science Museum, I thought some NASA videos I came across recently on YouTube would be of interest. These are a sampling of microgravity experiments by Science Officer and Expedition Six Flight Engineer Don Pettit on the International Space Station (ISS) as it orbited the Earth in 2003. Be sure to watch the tension break down at the end of the last one. WATER opened last week on January 30th (my birthday by the way) and runs through April 26, 2009.






More of these NASA science videos can be found at YouTube. WATER is a joint project of the Science Museum of Minnesota and the American Museum of Natural History.


For most of us, the first thing we think of when we hear the word "vacuum" is the common household appliance. However, that is not the only kind of "vacuum" that exists. To help expand "vacuums" beyond the common household definition, we, the Mentor Buzz team, have created a series of multimedia presentations on the word or theme of vacuums. As defined by the ever-venerable Wikipedia, a vacuum "is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure." A simpler definition of "vacuum" that we created is that a vacuum is a space that basically doesn't have air or has very little air in relation to how big the space or container is. Based on this definition, we split up into three groups and created three different projects that will hopefully explain some aspect of the science of vacuums: a video, a series of step-by-step experiments, and a game. Here is what we have created.



Frozen soap bubble: I am going to try this next time it is way below zero!
Frozen soap bubble: I am going to try this next time it is way below zero!Courtesy Sparkleice

I saw some photos of frozen soap bubbles that were way cool! (click on the red link to see them) If you try this, let us know how it worked and hopefully get some pictures to share.


Were you a fan of the Mentos and Diet Coke fountains that EepyBird created? If so, you might tune in to "Samurai Girl" tonight (7pm, ABC) to see EepyBird's experiments with more than 250,000 sticky notes. You can also check out an extended version of the video, complete with how-tos, at

Here's a sneak peek, but definitely check the EepyBird site tonight for more.


Sometimes it’s best to just let the door close.: Keeping your options open entails some very real costs--sometimes more than the option is worth.
Sometimes it’s best to just let the door close.: Keeping your options open entails some very real costs--sometimes more than the option is worth.Courtesy George Karamanis

“Keep your options open.” Sounds like good advice, right? Turns out, it has hidden costs.

Professors Dan Ariely and Jiwoong Shin at MIT ran an experiment to test rational behavior. Test subjects played a computer game. On the screen were three doors. If they clicked on a door, it opened. Click on it a second time, and a number would appear, and they would earn that much money. Click on a different door and it opens, but the first door closes. Some doors had higher average payoffs than others. The object of the game is to get as much money as you can in 100 total clicks. (You can play the game—without the money, sorry—here.)

Obviously, the winning strategy is to find the door that pays the best, and then keep clicking on it. But then the evil professors threw a curve. They presented a second version of the game, where the doors shrank and eventually disappeared if you didn’t click on them. Subjects would waste clicks keeping the lower-paying doors from disappearing. On average, they earned 15% less for the privilege of keeping their options open.

Ariely and Shin hypothesize that players kept the less-valuable doors open, even though it cost them money, to avoid the pain of losing the door forever. We all hate to lose things. But sometimes the cost of keeping them around is more than they are worth. The game is a good lesson in the value of just letting things go.

Over on the New Scientist's Short Sharp Science blog there is a great little experiment to try. Mix up some hot chocolate and tap your spoon on the bottom of the mug. As you do this the pitch of the tapping sound will change. Why? They don't know yet either. Any guesses?