With Halloween around the corner, you’ll love this bubbly, color-changing, stinky chemical reaction.  All you need is a head of red cabbage, vinegar and baking soda for this mad scientist experiment!

Click here for more detailed instructions. If you want to avoid the stove, chop half a head of red cabbage and blend it with about 3 cups of water. Strain the liquid through a colander and then through a coffee filter in a plastic bag with one corner cut off. Blended cabbage juice makes longer-lasting bubbles and turns a slightly brighter shade of blue!

What started out as a food science experiment turned into a seasonal one this morning, and we ended up outside pulling leaves off our Maple tree to see how the pigments from a red leaf would compare to those from a green one. Liquid chromatography allows you to separate the pigments (molecules that give plants color) using paper as a solid medium for the molecules to travel up, and alcohol as the solvent that separates and carries the pigments up the paper at different speeds, depending on how large they are.

To do this experiment, you’ll need a green leaf, and one or more that has turned color (we found a red and green one from the same tree!)  In addition, you’ll need a coin, a jar, a pencil, paper towels or coffee filters and rubbing alcohol. Young children MUST be supervised during this experiment since rubbing alcohol is a toxic substance if ingested!

Balance the pencil on the lip of the jar and cut a strip of paper towel or coffee filter long enough to hang (folded in half) over your pencil and dangle with both ends just above the bottom.

Draw a pencil line about half an inch above the bottom of the strip on one side.  Wrap a leaf around the coin (dimes work well) and press it down against the line on the left side, hard enough to rub color onto the line. (See photo above!) Do the same thing with the other leaf. Get as much color as possible onto each spot and let dry for a few minutes, or dry with a blow dryer.

Fill the jar with just enough rubbing alcohol so that the bottom of the strip will touch it, but the spots of color will not.  Hang your paper strip over the pencil with the bottom touching the alcohol. (You can have it doubled or have one half hanging outside the jar. Both worked for us.) Try to make sure that the strip is hanging evenly so the color will travel straight up.

Watch as the colors travel up the strip and take the strip out of the alcohol before they reach the top.  Let it dry and observe. The colors may be faint, but you should be able to make them out.

What do you see?  Green leaves contain a pigment called chlorophyll, which helps plants do photosynthesis (get energy from sunlight, water and carbon dioxide.)  In the fall, many trees stop making this pigment, which is why the other colors in the leaves become visible. Are your results consistent with this?

We tried the same experiment to compare spinach leaves that were fresh or had been microwaved in a ziplock (blanched). Although I read that the pigments change when vegetables are cooked or stored, we didn’t see much difference, except a brown smear near the very bottom.  What other veggies could you try this experiment with?

This morning, my daughter and I got out some white coffee filters and started playing with liquid chromatography, which is defined as: a process in which a chemical mixture carried by a liquid is separated into components as a result of differential distribution of the solutes as they flow around or over a stationary liquid or solid phase.

In other words, you can use chromatography to separate pigments, or color molecules, using water (the solute) to carry them up a strip of coffee filter (the solid phase.) Different molecules travel at different speeds, so you can see some of the many colors contained in a black marker as the pigments race up the strip.

You’ll need white coffee filters, or paper towels, cut into strips just long enough to hang over a pencil or ruler that is balanced on the lip of a jar or cup without quite touching the bottom of the jar. We cut wider strips and hung them over a ruler balanced on two water glasses over a tupperware container. Look at the pictures and you’ll get the idea. You want the bottom of the paper just barely touching the water and not touching the sides of the container.

To see what colors are contained in different markers, draw dots about half an inch above the bottom of the paper and drape the paper over the pencil, just letting the bottom of the strip barely touch the water. You don’t want to submerge the marker dots. Let the water travel up to the top of the strip to see good separation. (See top photos.) Black and brown markers are especially interesting.  Try several of them- they’re not all alike.

I was trying to think of a fun Halloween science experiment, so we came up with this variation on magic marker chromatography. Start by drawing faces with markers on the bottom of filter strips and hanging them over pencils on cups with the bottoms of the strip barely submerged in water at the bottom of the glass. The water will slowly travel up the paper, taking the pigment with it. It’s fun to watch the face blur and slowly disappear into line of color.

My daughter did this for an hour without getting bored. You can also do marker chromatography with thin strips of paper containing just one color or by dropping water on a dot you draw with a marker.

My kids brought “Angry Birds” to life this morning by making Marshmallow Slingshots and using them to launch their Angry Birds stuffed animals at a tower of blocks (with a stuffed pig on top, of course.)
Love it!!!
To make your own angry birds slingshot, all you need is a chair, some rubber bands, and a plastic ring like the ones they put on prescription bottles. Click here for directions and to learn more about slingshot physics.

We’ve enjoyed watching the Monarch caterpillar we found a few weeks ago transform from ravenous larva to jewel-like chrysalis.  Soon, a beautiful butterfly will emerge and my kids and I will cheer as it soars to the treetops.

It’s a great time of year to find Monarch caterpillars!  Look for some milkweed that’s been chewed up and you may find a caterpillar of your own to observe! Be sure to take some milkweed with you and keep it fresh so your caterpillar has plenty of food.  The last bunch of caterpillars that hatch out each summer are the ones that make the long trip to Mexico, where they’ll spend the winter before returning to your backyard.

There was a really neat article about Monarchs in the New York Times recently! Click here to read it.

You may have heard you can drain a fish tank with a siphon, but have you ever made one, just for fun?

With a few feet of clear, plastic tubing, you can create your own siphon, make a “roller coaster” for small objects,and watch physics in action.

You’ll need a long piece of flexible, plastic tubing (maybe 5 feet), a large container set off the ground, and another container to catch the water so you can reuse it. A hose is also helpful, if you’re outside.

Fill the upper container with water and put one end of the tube UNDERWATER in this container. For the siphon to work, one end must be submerged under water in the upper container and the other end must be lower than the level of the water! You can weight the upper end down to keep it submerged.

There are several ways to start the siphon. You can submerge the entire piece of tubing in the water to remove all the air, put your thumb over one end, remove it from the water and lower it below water level before removing your thumb to start the flow. Alternately, we’ve found it’s easiest to put one end of the tube in the upper container, have the other end out and lower than water level and then put the running hose to the underwater, upper end of the tubing to remove all the air and start the water running out of the lower end. Remember to keep the upper end underwater or your siphon won’t work!