Category Archives: Science fair ideas

Homemade Photovoltaic Cell

1943FebRadioCraftSeventy-five years ago this month, the February 1943 issue of Radio Craft showed how to make this rudimentary photovoltaic cell.

With some modification, it scould be easily duplicated today, and could be the basis for an interesting science fair project.

It consists of a strip of lead, as well as a copper plate covered with cuporus oxide.  To achieve the coating, the copper plate is heated in a flame until it is covered by a black flaky substance, which is cupric oxide.  Then, it is washed in a weak solution of ammonia, which reveals the light-sensitive cuprous oxide.

A sheet of lead should be available at a craft store, or can be ordered from Amazon.  Similarly, a small piece of copper is readily available at a hardware store or Amazon.

The electrolyte is a somewhat more difficult proposition.  The lead nitrate is somewhat hazardous, but should be safe if handled carefully.  The main problem is that it is expensive.  It is available on Amazon, both as a solution and as crystals,  However, the prices might be outside the young mad scientist’s budget.

Fortunately, this site seems to suggest that ordinary salt water will function adequately as the electrolyte.  Therefore, one suitable science fair project might be to determine what other electrolyte solutions might work best.  All that would be required would be a voltmeter to see which configuration puts out the most electricity.  The advanced student could skip buying the voltmeter and instead make this simple galvanometer.

Another fun project would be to demonstrate communication over a light beam, with a setup similar the one on this site.  Your homemade photocell is hooked to the input of a small audio amplifier, and you hook an LED to the headphone jack of a radio or other audio source.

1928 Soviet Crystal Set & Galvanometer Experiments

1928No1RadioLThis illustration of a handsome crystal set listening post comes from 90 years ago, in 1928 issue number 1 of Радиолюбитель (Radio Amateur) magazine, illustrating an article by A. Pushkov.

Elsewhere in the magazine, it’s apparent that, just like their Western counterparts, young Soviet experimenters discovered the fun that could be had with a milliammeter, although I have to admit that I never thought to conduct the second and fourth experiments shown here:


(The piece of metal in the above diagram is marked “железо”, iron.)


The sensitive galvanometer was probably a valuable instrument in the 1928 Soviet Union.  Modern students desiring to reproduce these experiments can do so very inexpensively with a digital voltmeter such as the ones shown here:

1967 Blast Furnace For Young Soviets

1967NovSovietI’m not able to make out the text, but this Soviet magazine from November 1967 appears to be right up our alley. It appears to be giving young comrades instructions for building a home blast furnace!

I am able to make out the caption for the item between the vacuum cleaner and the wall outlet, and it’s marked “rheostat.” Presumably, it’s set to blow air into the combustion chamber, and the young Soviet mad scientist can adjust the intensity of the furnace with the rheostat.

The illustration appeared in the November 1957 issue of Юный техник magazine.  A treasure trove of similar magazines, many on the subject of radio, can be found at Журналы СССР.

Contrary to first impression, the logo at the top of the page is Ют, the abbreviation for the name of the magazine. But if it looked like HOT at first glance, we don’t blame you. This contraption will indeed get hot!

We put this item in the “science fair ideas” category. However, we do recommend that before duplicating this project, young scientists should have the article translated to see if it contains any safety warnings. I suspect some might be called for.

Fun With Explosive Gasses, 1937

1947OctPS1With it being unfairly accused of responsibility for many a UFO sighting, the humble substance known as swamp gas today has an undeservedly bad reputation. But this was not the case for this gentleman using swamp gas as part of his scientific inquiry, following the plans set forth in the November 1937 issue of Popular Science, in an article with the title of “Fun With Explosive Gasses.” With a title like that, you can bet that it’s going to appear on these pages.  The article notes that hydrocarbons can be the subject of many spectacular experiments by the amateur chemist, and details a number of explosively good experiments.

The article begins tantalyzingly with some of the possibilities:

Would you like to get gas from coal without heating the coal? To make an inflammable gas that will dissolve in certain liquids as easily as sugar does in coffee? To produce a gas that burns with a flame you can hardly perceive? Or to create fiery bublles of gas, jumping about like grasshoppers, from simple everyday chemicals? These are some of the curious and interesting experiments with hydrocarbon gasses that any amateur chemist can easily perform.

The gentleman in the illustration is collecting methane, the gas that bubbles up through the water of marshes. He is collecting it by stirring up the muddy bottom and trapping the ascending bubbles under an inverted funnel.

For those without a nearby swamp, the article also explains how to mix up a batch in the lab.

The article also explains how to make acetylene. This involves first creating some chlorine gas, capturing it in a bottle, and then adding some calcium carbide and water. As the resulting acetyline reacts with the chlorine gas, it produces a flash of light and a tiny cloud of soot. “With the bombardment proceeding at the rate of several explosions a second, the bottle resembles a miniature battlefield.”

For the aspiring young mad scientist, this article should be great inspiration for a first-place science fair project.



Calibrating Your Watch With The Stars

1947OctPSSeventy years ago, the October 1947 issue of Popular Science showed this method of making sure your watch was accurate.

While this method would not, by itself, give you the exact time, it would very precisely tell you the elapsed time.

The method was very simple. You simply installed a piece of tin with 1/16 inch hole on some fixed location, such as the side of the building. You used it to sight a vertical fixed object, such as a lightning rod or distant skyscraper. Then, you observed the exact time that any star was occluded by the object. Since the star is essentially a point of light, it would disappear suddenly. You noted the time.

Then, the next evening, you would observe the same star. It would be occluded exactly 23 hours, 56 minutes, 4.09 seconds later–one sidereal day. In other words, the time on your watch should read exactly 3 minutes 55.91 seconds before the previous night’s figure.  (For all practical purposes, a sidereal day is 364/365 of a solar day.  This makes sense, since the Earth itself has moved 1/365 of its way around the sun in 24 hours.)

Depending on whether your watch was fast or slow, you could thus adjust the spring.

If you knew the exact time the first night, then you could also create a table showing the exact time of occlusion subsequent nights. As long as you didn’t move the piece of tin, you would always know what time it is.

This method has two applications.  After the zombie apocalypse, presumably WWV will be off the air.  The stars give you a method to keep your clock calibrated very accurately.  It could also be the basis for a very interesting science fair project.



Science Fair Ideas: Fun With Air Pressure (With Optional Explosive Gas)

1937OctPS3Is it just me, or is there a slightly diabolical look on this young woman’s face?  This picture appeared in the October 1937 issue of Popular Science, meaning that it was probably taken right around the time of the Hindenburg disaster.

She is preparing what was probably the first place experiment in the 1937 science fair by filling soap bubbles with hydrogen gas.  The magazine carried a number of scientific experiments involving air pressure.  Most were very safe, even by our modern standards.  But instead of settling for those completely safe experiments, she decided to generate some hydrogen gas.  Normally, soap bubbles fall, because they’re heavier than air.  But by blowing soap bubble with hydrogen gas, they rise to the ceiling.

Hopefully she didn’t try to relax by lighting up a Camel while doing the experiment, since the magazine (perhaps with the Hindenburg fresh in the memory) warned that the experiment should be “kept safely away from open flames.”  The hydrogen gas is easily generated in a flask or bottle containing scraps of zinc. To make the hydrogen, you simply add a little bit of sulphuric or hydrochloric acid.  This 10% HCl toilet bowl cleaner will probably do the trick.  You should be able to find some inexpensive item made out of zinc at the hardware store.  If you can’t, you can probably use galvanized nails, or just buy a small piece of the metal.

1937OctPS1If your parents or teacher are uncomfortable with you playing with dangerous chemicals and explosive gasses, then the article includes some other less dangerous experiments.  Perhaps you can start with one of these to convince them that you use good lab practices.

For example, shown at the left is a simple experiment showing the effects of air pressure.  You first inflate a balloon inside a bottle.  The magazine didn’t tell you exactly how, since they realized that kids 80 years ago could figure it out themselves.  You can also figure it out yourself, but just in case you can’t, simply insert the uninflated balloon into the top of the bottle, blow it up part way, tie it off, and then poke it in.

1937OctPS4Once the balloon is inflated, you seal up the bottle and either blow air in or suck air out.  The balloon will expand and contract depending upon the pressure in the bottle.  The same general principle is used to construct the barometer shown here.  If the barometer isn’t quite sensitive enough to respond to changes in barometric pressure (or if you’re impatient), then you put it inside a larger container and blow in or suck out air to make the barometer show the changes in pressure.

Finally, the magazine showed how to weigh air, using a system similar to what we previously showed for weighing smoke.  As shown below, you put a little bit of boiling water in a jar and firmly seal the lid.  As the water cools, the steam in the jar condenses, leaving a partial vacuum.

After it cools, you carefully weigh the jar.  Then, you loosen the lid, to allow air to rush in.  The total weight increases, and the difference is the weight of the air.




Glow In The Dark Home Experiments

1937OctPSEighty years ago, the October 1937 issue of Popular Science showed the aspiring young scientist how to perform  the “most mysterious and beautiful of chemical experiments” by producing substances that glow in the dark. Fortunately, all of the materials required are readily available today. In fact, the young Einstein will probably discover that most of them are already in the kitchen or garage.

While the effect is not as strong as with other chemicals, many of these glow-in-the-dark formulas can be prepared with items already in the kitchen. Among these was chili powder (the stronger the better). The magazine noted that “a single can of chili powder from the grocery store will be enough for innumerable experiments.” Paprika, as well as other items, could also be used. Mom will be happy to learn that it was a “fascinating pastime to try out a little of everything on the pantry shelf, to see what substance will give the strongest light.”

To make these household substances glow, it was necessary first to steep a little alcohol on the item. Then, you would add some lye and hydrogen peroxide.

The final ingredient was new in 1937, judging from the explanation: “One of the newer, ‘made with electricity’ bleaching liquids and laundry whiteners. There are several of these liquids, widely advertised and obtainable at any grocery store. They are solutions of sodium hypochlorite, and you will find that this statement appears on the labels of the bottles.”

Eighty years later, we just call this “household bleach,” and the most famous brand name is Clorox.

For a stronger effect, the article recommended substituting the chili powder with oil of bergamot, which was available at the drug store. I don’t know if you can find it at the drug store today, but as with everything, it’s available at a reasonable price on Amazon, at this link.  According to the Amazon description, this “essential oil” (I’ve always wonder why nobody uses non-essential oils) is “helpful in soothing the mind and body with aromatherapy” and is safe for topical application.  But it’s a lot more fun if you get it to glow in the dark.

For the strongest effect, the article recommended 3-aminophthalhydrazide, more commonly known as luminol  (according to the article, not to be confused with luminal, a barbiturate drug).  It’s also available from Amazon at reasonable price at this link.  With this chemical, spectacular displays, such as the ones shown at the top of the page, are possible.

The article includes even more suggestions for glow-in-the-dark experiments.  The young scientist looking for something spectacular for the next science fair will undoubtedly find much inspiration from this old article.

Of course, you can save time buy just buying a bunch of glowsticks like the ones shown here and just cutting them open.  But it’s probably a lot more fun to make your own, and this old article tells you exactly how.

Fun With Arsenic: 1927


What could possibly go wrong here?

Ninety years ago, the September 1927 issue of Science and Invention magazine carried this article for aspiring young chemists with some educational and fun experiments they could do with arsenic. After a brief historical introduction ot the element, the article jumped right in with some practical experiments the young chemist could do at home.

For example, the amateur chemist could take some arsenic, presumably procured from the friendly neighborhood pharmacist, and reduce it at home to produce a purer oxide of the element. This was done by placing it over a porous plug of asbestos (also presumably readily available from the local hardware store), putting it in a test tube with some charcoal, and then placing it over a bunsen burner. This produced a vapor of arsenic trioxide, which was captured in another test tube. “When cool, the arsenic can be shaken out upon a piece of paper.”

The article also showed how to conduct a test for arsenic, with which “amounts of arsenic as small as a fraction of a milligram can easily be detected.” Perhaps the author included this bit of information as a warning, lest the young chemist allow a fraction of a milligram to “accidentally” be ingested by someone.

It also showed how to make a lovely green dye, known as Scheele’s green. Apparently, political correctness had already made a foothold by 1927, since the article pointed out that this green dye had previously been used in wallpaper. According to the article, “this caused a great deal of unnecessary excitement, for it was thought that you could be poisoned from it.” But this concern was entirely unwarranted, since “unless some was rubbed off accidentally and eaten, there is absolutely no danger.”

The article did caution, however, that the young chemist should “be very careful with it, as it is very poisonous.”

Warning:  This article is from 90 years ago.  You can’t buy arsenic from your local pharmacist any more.  Even if you could, the experiments described in this article sound very dangerous, and I would not recommend attempting any of them.  Those arsenic vapors sound like a really bad idea.  Besides, you can’t get asbestos either.  So even though the only category I had to put this article under was “Science Fair Ideas,” I don’t think this is a good choice.  But for more science fair ideas, some of which are just dangerous enough to be fun, you can see them all at this link.

Science Fair Idea: How to Weigh Smoke


Sir Walter Ralegh by 'H' monogrammist.jpg

Sir Walter Raleigh. Wikipedia image.

Sir Walter Raleigh is reputed to have won a bet with Queen Elizabeth that he would be able to weigh the smoke coming from his pipe. After she accepted the bet, he weighed a pinch of tobacco, smoked it, and then weighed the resulting ashes. He convinced the Queen that the difference in weight was the weight of the smoke.

Of course, the Queen could have won the bet by pointing out that the combustion products contained oxygen, and most of that oxygen originated not in the tobacco, but in the air. But she didn’t think of that, and instead paid the bet.

This little experiment, from 80 years ago, takes into account the amount of oxygen, and proves that the total mass doesn’t change during the combustion process. You do this by placing some matches inside a sealed glass flask. You carefully place it on a balance. Since the matches are sealed inside, you’re not able to strike them. To ignite them, you heat up the outside of the glass. Eventually, the matches will burst into flame and burn until all of the oxygen in the flask is consumed.

The balance won’t move, since the weight inside the container remains exactly the same. The weight of the matches plus the oxygen will exactly equal the weight of the burnt matches plus the weight of the smoke. Since it’s all sealed inside the same container, that weight won’t change.

If you wanted, you could take it a step further and repeat the experiment with the flask open.  In this case, the matches would burn longer.  Oxygen would be able to go in, and the smoke would be able to go out.  Therefore, the weight would change.  Would it go up or down?

You can easily adapt this idea to your next science fair assignment with a hypothesis along the lines of, “mass is conserved during combustion.”  While that other kid is busy fumbling with the paper mache volcano, the teacher will be suitably impressed that you’re smarter than Sir Walter Raleigh, and you’ll undoubtedly go home with the first prize.

The photo and experiment appeared in the August 1937 issue of Popular Science.

Sciene Fair Idea: Measuring Wind Resistance

1937MayPSWindIf Junior just remembered that the Science Fair project is due tomorrow, and he hasn’t even started, there’s no need to panic. The little project shown here can easily be whipped up in an evening, and the teacher will be none the wiser about your haste. He or she will assume that the little scientist has been working on it for weeks.

While Mom and Dad race to the dollar store before it closes to buy the poster board and markers, Junior can start building this instrument for measuring wind resistance for objects of various sizes. Unless someone sticks their fingers into the moving fan blades, this experiment should be completely safe. It appeared 80 years ago this month in the May 1937 issue of Popular Science.

Of course, the teacher expects the students to come up with things like a hypothesis, which should be pretty easy.  All Junior needs to do is come up with a sentence such as “a ______ shaped object has more wind resistance than a ______ shaped object.”  The blanks can be filled in with whatever objects are easier to construct, for example, a cube and a sphere.

The instrument shown here is pretty self-explanatory.  The object being tested is mounted on top of a rigid wire, with a counterweight at the bottom.  To make it look fancy, you can make the pointer and scale.  Then, you balance the wire and blow a fan at it.  The object that deflects the furthest has the greater wind resistance.

As can be seen here, the fan has an “egg box partition” in front of it to straighten out the air currents.  Apparently, in 1937, most households had egg boxes lying around with cardboard partitions.  A modern egg carton probably won’t work, but Junior can retrieve some cardboard from the recycling bin and simply make a grate consisting of square openings.

When you get home with the poster board, Junior can copy down some interesting facts from the Wikipedia article about drag, and the result will probably be a blue ribbon.