Archive for February, 2009

Microwaving Soap

When you warm up leftovers, have you ever wondered why the microwave heats the food and not the plate? (Well, some plates, anyway.) It has to do with the way microwaves work.

Microwaves use dielectric heating (or high frequency heating) to heat your food. Basically, the microwave oven shoots light beams that are tuned to excite the water molecule. Foods that contain water will step up a notch in energy levels as heat. (The microwave radiation can also excite other polarized molecules in addition to the water molecule, which is why some plates also get hot.)

The following experiment is a quick example of this principle using a naked bar of Ivory soap. The trick is to use Ivory, which contains an unusually high amount of air. Since air contains water moisture, Ivory also has water hidden inside the bar of soap. The microwave will excite the water molecules and your kids will never look at the soap the same way again.

Toss a naked bar of Ivory soap onto a glass or ceramic plate and stick it into the microwave on HIGH for 2-3 minutes. Watch intently and remove when it reaches a “maximum”. Be careful when you touch it after taking it out of the microwave oven – it may still hold steam inside. You can still use the soap after this experiment!

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Survival Tips for Science Fair Projects

We’ve posted this before, but here’s a recap in case you missed it:

Survival Tips, Part 1

Survival Tips, Part 2

Survival Tips, Part 3

Happy Experimenting!

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Crystal Radios

We’ve had more than a few emails asking WHEN our crystal radio project would be out… so I wanted to be sure to let you know that it’s ready right now!  We cover several different crystal radio designs, including tuning coils and variable capacitors, in this one project.  If you’ve ever wanted to make a radio that doesn’t require batteries, this is the perfect project for you.  Here are the latest images from the radios we cover in the kit:

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Underwater R.O.V. Robot

This is one of my favorite projects, as it really teaches the kids how to make switches that power a motor both forward and reverse as well as chassis design and waterproofing thrusters.  Kids that make this R.O.V. project are often surprised by how much of a role buoyancy plays out in their robot, but with a few tweaks here and there, their underwater submersible can be zooming around in no time!  I thought you’d like to see a few of the images we’ve had sent to us over the years we’ve taught this project:

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More on Borax Crystals

Okay, so after that last email we sent about substituting laundry whitener for sugar, we received a flurry of emails, asking for more specific directions!  Well, here they are…

Grow beautiful crystals using laundry soap! In an OLD saucepan (like one you only use for science experiments), add a few cups of water and enough borax so that you can’t dissolve any more borax into the water (you”ll see sediment particles on the bottom of the pan). Turn on the heat to medium and stir with an OLD spoon (again, from your science tools) and when the sediment disappears, add a bit more borax… and stir… and when that disappears, add a bit more borax… and stir… and when that disappears… you get the idea!

You’re creating a super saturated solution here. When you can’t dissolve any more borax to the solution, and a bit of water and turn off the heat. Let cool to 130 deg F and pour into awaiting glass pickle jar. Balance a pencil across the mouth of the jar and suspend either a length of string or a pipe cleaner twisted into interesting shapes (like a snowflake, or a dog, etc…) Leave for about 6 hours and then check back. Crystals will grow to full size overnight if you’ve set up your solution just right.

Keep your eye on it, though, because these crystals not only grow quickly, but once the crystals from the pipe cleaner touch the ones growing on the sizes of the jar, you won’t be able to extract your shape! (Unless, of course, you want to grow a geode…)

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Building a Mad Science Lab

Turning your kitchen table into a Mad Scientist Laboratory!


Chemistry is an exciting subject for kids of any age, especially if you set up a natural discovery environment for them to safely explore in. Let’s find out how to do this with your own homeschool science learning environment.

At a university, one of the first things you will learn about in your chemistry class is the difference between physical and chemical changes. An example of a physical change happens when you change the shape of an object, like wadding up a piece of paper. If you light the paper wad on fire, you now have a chemical change. You are rearranging the atoms that used to be the molecules that made up the paper into other molecules, such as carbon monoxide, carbon dioxide, ash, and so forth.

How can you tell the difference between physical and chemical changes? There’s an easy way to tell if you have a chemical change: if something changes color, gives off light (like the light sticks used around Halloween), heat is absorbed (gets cold) or produces heat (gets warm). Some quick examples of physical changes include tearing cloth, rolling dough, stretching rubber bands, eating a banana, or blowing bubbles.

Let’s mix up chemicals that bubble, ooze, freeze, and change colors. Before we start, you’ll need to get these items together: a muffin cup baking tray, water, vinegar (acetic acid), baking soda (sodium bicarbonate), washing soda (sodium carbonate), rubbing alcohol, hydrogen peroxide, citric acid, ammonium chloride (don’t activate the cold pack, but instead cut open and empty the contents into a plastic bag and discard the water pouch inside), aluminum sulfate (“alum” in the spice section of the grocery store or drug store), a head of red cabbage and a clear liquid dish soap such as Ivory.

Cover your kitchen table with a plastic tablecloth (if you have small kids, put another tablecloth on the floor to catch the spills). Place your chemicals on the table. A set of muffin cups make for an excellent chemistry experiment lab. (Alternatively, you can use empty plastic ice cube trays.) You will mix in these cups. Leave enough space in the cups for your chemicals to mix and bubble up – don’t fill them all the way when you do your experiments!

Shopping List:

• Rubbing alcohol (largest bottle)
• Hydrogen peroxide (largest bottle)
• Baking soda (largest box you can find)
• Distilled white vinegar (largest size)
• Washing soda (near the laundry soap)
• Citric acid (optional, but nice to have)
• One head of red cabbage
• Clear ivory dish soap (small bottle)
• Alum (check the spice section)
• Single-use cold pack ( not the gel kind)
• Plastic zipper bags and old water bottles
• Muffin cup baking tray (12 cups or more)

Set out your liquid chemicals in easy-to-pour containers , such as water bottles (be sure to label them, as they all will look the same): alcohol, hydrogen peroxide, water, acetic acid, and dish soap (mixed with water). Set out small bowls (or zipper bags if you’re doing this with a crowd) of the powders with “scoopers” made of the tops of your water bottles. The small “scoopers” regulate the amounts you need for a muffin-sized reaction. Label the powders, as they all look the same.

Although these chemicals are not harmful to your skin, they can cause your skin to dry out and itch. Wear gloves (latex or similar) and eye protection (safety goggles), and if you’re not sure about an experiment or chemical, just don’t do it. (Skip the peroxide and cold pack if you have small kids.)

What about the red cabbage? Red cabbage juice has anthocyanin, which makes it an excellent indicator for these experiments. Anthocyanin is what gives leaves, stems, fruits, and flowers their colors. Did you know that certain flowers like hydrangeas turn blue in acidic soil and turn pink when transplanted to a basic soil? This next step of the experiment will help you understand why. You’ll need to get the anthocyanin out of the cabbage and into a more useful form, as a liquid “indicator”.

Prepare the indicator by coarsely chopping the head of red cabbage and boiling the pieces for five minutes on the stove in a pot full of water. Carefully strain out all the pieces (use a fine mesh strainer) and the reserved liquid is your indicator (it should be purple).

When you add this indicator to different substances, you will see a color range: hot pink, tangerine orange, sunshine yellow, emerald green, ocean blue, velvet purple, and everything in between. Test out the indicator by adding drops of cabbage juice to something acidic, such as lemon juice and see how different the color is when you add indicator to a base, like baking soda mixed with water.

Have your indicator in a bottle by itself. Old soy sauce bottles or other bottles with a built-in regulator that keeps the pouring to a drip is perfect. You can also use a bowl with a bulb syringe, but cross-contamination is a problem. Or not – depending if you want kids to see the effects of cross-contamination during their experiments. (The indicator bowl will continually turn different colors throughout the experiment.)

Your mission: To find the reactions that generate the most heat (exothermic), absorb the most heat (endothermic), and which are the most impressive in their reaction (the ohhhh-ahhhhh factor).

The Experiment: Start mixing it up! When I personally teach this class, let them have at all the chemicals at once (even the indicator), and of course, this leads to a chaotic mix of everything. When the chaos settles down, and they start asking good questions, I reveal a second batch of chemicals they can use. (I have two identical sets of chemicals, knowing that the first set will get used up very quickly.)

Tip for Testing Chemical Reactions: Periodically hold your hand under the muffin cups to test the temperature.

After the initial burst of enthusiasm , your science students will intrinsically start asking better questions. They will want to know why their green goo is creeping onto the floor while someone else just bubbled up hot pink, seemingly mixed from the same stuff. Give them the change to figure out a more systematic approach, and ask if they need help before you jump in to assist. Use the indicator both before and after you mix up chemicals, and you will be surprised and dazzled by the results!

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Homemade pH

An indicator is a compound that changes color when you dip it in different things, like vinegar, alcohol, milk, or baking soda mixed with water. There are several extracts you can use from different substances. You’ll find that not all indicators are affected by both acids and bases. Some only change color for just an acid, or just a base. Turmeric, for example, is only good for bases. (You can prepare a turmeric indicator by mixing 1 tsp turmeric with 1 cup rubbing alcohol.)

Easy Indicator Juice
Cut the substance you want to turn into your”indicator” into small bits. Boil the chopped substance for five minutes. Strain out the pieces and reserve the juice. Cap the juice (indicator) in a water bottle and you’re ready to go. What different substances can you use? We’ve had the best luck with red cabbage, blueberries, grapes, beets, cherries, and turmeric. You can make indicator paper strips using paper towels or coffee filters. Just soak the paper in the indicator, remove and let dry. When you’re ready to use one, dip it in part way to you can see the color change and compare it to the color it started out with.

Turn this into a science fair project! Make sure you only change ONE thing when you transform this into a science fair experiment…. you can change the type of substance you use, or the stuff you test with the indicator.  For example, you could try beets,  blueberries, grapes, cabbage, cherries, and turmeric and test lemon juice with the different pH strips.  OR you could make a cabbage-based indicator and test lemon, limes, oranges, etc.  Have fun!

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Light Speed, Part 2

In this blog article, I mentioned how you could measure the speed of light the easy way.  Did you know there is an even EASIER way to do it?  Check out this super-easy method – all you need is a microwave and food.

And I promise to share with you how to do it the hard way in Part 3.

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Alternative Energy Projects

Being green is red-hot right now, so it’s not surprising how many emails we get asking how kids can do ultra-cool science fair projects on alternative energy.  One of the best ways to start is to visit a toy store and pick up a kit that has a solar cell, solar motor, and propeller combination.  Once you have these items, it’s easy to power things like race cars, solar boats, etc.  Here are a few images from our own Solar Power science fair project kit to get you started on ideas:

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