Note: Be prepared for a mess (we did these outside). We supplied goggles, which we had purchased at a home supply store.

1. Density

Gather:

• periodical table of the elements
• accurate kitchen scale
• two or more objects of the same size made of different metals, for example the zinc and copper plates from a lemon battery kit

Ask the children if they predict the two objects will weigh the same (because they are the same size). If not, can they use the periodical table to figure out which will weigh more? Use the kitchen scale to test their prediction.

The Intermediate Physical Science Kit from Exploration Education has the materials for this activity, including supplies to make your own working balance.

2. A Density Column

A density column is made of liquids of different densities layered one over another.

Gather

• clear container (I used a water pitcher) big enough to accommodate the ladle)
• corn syrup
• water
• food coloring
• cooking oil ( I used canola)
• isopropy alcohol (standard rubbing alcohol)
• soup ladle
• items to test, such as crayons, pennies, hard candies, toothpicks

Ask the children to predict which liquid is the most dense and which is the least. Pour about an inch of corn syrup in the bottom of the container. Add a few drops of food coloring to the water. Hold the ladle with the bottom resting at the top of the corn syrup layer and slowly pour in an inch or so of water. Gently empty the ladle move it up and pour in the cooking oil. Again empty the ladle, move it to the top of the cooking oil layer and gently add a layer of rubbing alcohol. You may also want to add food coloring to the alcohol layer.

Once you have a column, then test how other materials float in the layers. The pennies should be the densest and fall to the bottom. We dropped in Mentos candies, which are made of sugar and glucose syrup, and found they were roughly the same density as corn syrup. The crayons are made of wax, and floated in the oil layer. Our toothpicks were the lightest of all and floated on the alcohol.

We designed our density column based on a video at the Happy Scientist website.
We also found examples at Steve Spangler Science:
Bubbling Density Concoction
and
Seven Layer Density Column

Science is Fun in the Lab of Shakhashiri has a Layered Liquids demonstration as well.

3. Elephant’s toothpaste – recommended for outdoors where messy soapsuds won’t be a problem.

Gather:

• empty plastic water bottles – enough for each child
• hydrogen peroxide (the kind you get at the grocery store works fine)
• baking yeast
• water (food coloring optional)
• dish detergent (we used Dawn)
• funnel
• 1/2 cup measuring cup

Using a funnel, add 1/2 cup of peroxide and a ’squirt’ of dish detergent to each water bottle. In another container, mix roughly two teaspoons of yeast with about 1/4 cup water for every two bottles hydrogen peroxide (doesn’t need to be perfect). If you have a lot of children, you may need two or three containers of yeast/water. Shake or stir the yeast/water, and then pour a couple of tablespoons into each bottle containing the hydrogen peroxide/dish detergent mix. The concoction should erupt in a foamy volcano. Note: this is an exothermic reaction, which means the reaction gives off heat. Allow the children to explore the foam and some may notice the warmth.

The yeast in this reaction supplies the enzyme catalase. Oxygen is rapidly released causing the foamy bubbles in the soap.

For a much more detailed recipe, see Steve Spangler Elephant’s Toothpaste

4. Acids and Bases

Is it an acid or a base?

Liquids tested:

• lemon juice
• dish detergent
• ammonia
• vinegar

The first day we used the standard red cabbage indicator (red cabbage leaves ground in a blender with a bit of water) but the smell was unpleasant.

The next day we used frozen mixed berries ground in the blender with a bit of water. The mixed berries smelled better, although they didn’t give quite as good a range of colors.

Previous post about color and acids and bases

Steve Spangler’s Red Cabbage Experiment

Science is Fun in the Lab of Shakhashiri has an Exploring Acids and Bases Demonstration

If you children are tired of the standard red cabbage indicator, try mixing a little tumeric (spice used in curries) and rubbing alcohol in a small container and then dip in strips of paper towel. Watch out, tumeric will stain like crazy! Allow the paper towel strips to dry on a newspaper.

The tumeric solution makes a lovely yellow color. Once the strips are dry, test your acids and bases again.

We found the acids did not change the color of the strips, but bases made them turn a startling red.

We also used the tumeric/alcohol to write messages on orangy-yellow paper and after they were dry, revealed the “secret message” by lightly spraying with a household cleaning product that contained ammonia.

5. Using chemicals to make light

See Glowing Chemistry for more information

Extensions:

For the person interested in kitchen chemistry, try

Kitchen Science Activities

and Food Science 101 (the chemistry behind a simple cake)

For those interested in learning the names of the elements and their symbols:

Chemical Elements: Origins of Names Trivia Quiz

Free Rice has a chemical symbols challenge

Chemistry is great fun. Hope this inspires you to do some hands-on chemistry, too.

The Switzer brothers, Bob and Joe, were interested in science, probably due to the fact their father was a pharmacist. When Bob had a bad accident that kept him confined to home, his brother Joe kept him company by playing around with an ultraviolet lamp (also called a black light). Joe had a magic show and he was interested in fluorescent paints to develop a new magic trick. After finding commercial uses for fluorescent paints that would shine under ultraviolet, the brothers continued to experiment until they found a paint that would glow in regular daylight, not just under ultraviolet light. They had created the eye-popping Day-Glo colors found today in products as diverse as highlighters and traffic cones.

1. Glowing under ultraviolet light

Gather:

• a black light
• petroleum jelly
• paper
• tonic water
• kitchen or latex gloves (optional)

Here in Arizona, black lights are easy to obtain from virtually any hardware or home supply store, and for a good reason. It turns out that one of the best ways to find scorpions, which are active at night, is to shine an ultraviolet light on them. Scorpions glow under UV light. For those of you who are curious, Firefly Forest has a great photograph of a glowing scorpion.

How Stuff Works (site has ads) has an explanation of how a black light works. Basically, we can’t see ultraviolet light, but when it hits certain objects, forms of light that we can see are released.

Turn off the lights at night, and explore with the black light. What glows? Turn the lights back on and write a simple message in petroleum jelly on a sheet of paper (using the gloves if you don’t like the feel of the jelly). What happens when you turn the lights back off? What happens if you get petroleum jelly on your hands? Take a look at the tonic water and other household items under the black light, too.

For more black light science experiments, check Home Chemistry.

2. Light sticks

The light sticks that glow in the dark don’t need to be exposed to light or ultraviolet light to work. They are the result of a chemical reaction. How Stuff Works also has a section about how light sticks work.

Steve Spangler has a video about light sticks, and suggests an activity comparing the speed of the chemical reaction in warm water versus cold water, as measured by the amount of glow.

3. Day-Glo

Charlesbridge, the publisher of The Day-Glo Brothers, has an excellent animation of how Day-Glo pigments work. Go see it!

Entomologists who want to study insect movement sometimes use Day-Glo powders. They mark a group of insects with the bright powder, release them and then recapture the insects after a given period of time, to see where they ended up. This type of experiment is called a mark-recapture experiment. Insects may be recovered with simple equipment, like a butterfly net, or elaborate collecting equipment, such as a huge insect vacuum.

4. Glowing plastic stars

Younger children love the glowing plastic stars. Use them to create constellations, patterns, etc. My son used to like to throw light-charged plastic stars into the bathtub water and turn off the lights (briefly and with supervision). It was fun to see the stars swirl through the water.

Have fun. Who knows where an interest in light and chemistry will lead next?

Disclosure:  As a round II Cybils judge, I received a copy of this book for review purposes.

When I found the Home Chemistry blog, I was excited because there was a post about the “Chemistry of Colored Bubbles.” I have been wondering if you could make a colored bubble for ages. Now I know you can!

I think I mentioned this in a previous post, but Off the Shelf Chemistry has hands-on activities for teaching high school level chemistry with things more or less from around the house.

The home of National Chemistry Week 2009! is the American Chemistry Society. Their 2009 theme is “Chemistry—It’s Elemental!” They have a lot of resources, so plan to spend some time looking around.

About.com has a whole list of projects as well as good basic chemistry information.

Finally, Robert Krampf at the Happy Scientist has a number of chemistry experiments. Some of his experiments are free, but most require a subscription. He does have a free newsletter that has general science topics called Experiment of the Week.

And of course we have some chemistry experiments here, like Colors with Acids and Bases.

Hope you enjoy chemistry week!

If you have any great chemistry sites that I have missed, please leave them in the comments.

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!