Not your usual experiment, this is a book: “The League of Scientists” is a young adult fiction book by Andy Kaiser (the creator of Digital Bits Science Lab).

Equipment needed:

The League of Scientists is available here: http://www.LeagueOfScientists.com

The Digital Bits Science Lab Experiment:

The League of Scientists is a group of smart kids who love science. They use their knowledge and critical thinking skills to solve seemingly-supernatural mysteries.

One of the components of the book is the mystery aspect, and not just the “main” mystery. In most chapters, there is a puzzle. The solution to the puzzle involves the application of science or critical thinking. The book is intended to give science education (and scientific applications – something you don’t always get from such fiction) while still giving kids a good story and characters.

Equipment needed:

Two measuring cups (one cup must be able to hold at least two cups)

Water

Sugar

One spoon

The Digital Bits Science Lab Experiment:

Make sure that your cup of water and your cup of sugar are filled up precisely.

What do you think will happen when you pour the cup of sugar into the cup of water? You might think that you’ll get a result of two cups of a water/sugar mixture. Let’s try it: Pour the sugar into the water. Stir with the spoon.

Note what happened: one cup of sugar added to one cup of water does not give us two cups!

What’s happened? Why does one plus one not make two? We’ve created a “solution”, and this has interesting properties. A solution is when you mix ingredients, and those ingredients may undergo a physical change as part of that mixing. In this case, our sugar changes physically. Much of it dissolves in water. This is happening on a molecular level – the sugar seems to take up less room, because it’s using the extra space between the water molecules! The density of the water is greater now – we have more molecules crammed into the same space.

On a big scale, this is how the Earth’s oceans are salty, even though we can’t see that salt. Water looks like it may take up a lot of space, but there’s plenty of room to share.

Description: Dissolved copper can be plated onto a metal surface using electricity. Learn how electroplating works.

Equipment needed:

Copper Sulfate. This is one of the most soluble copper compounds, it makes bright blue crystals and dissolves fairly easily in water. You can buy it in hardware stores in several forms, the form I found was Roebic Root Killer (used to clear roots out of sewers and septic systems).

Click the photo to view the larger-sized picture.

A small DC power supply.  A “wall-wart” power adaptor like this one works fine.  I expect that pretty much everyone has at least one or two of these around, orphaned when the electronic gadget that it went with broke down. This power supply came from . . . from . . . well, to tell you the truth, I don’t know what it came from.  All I know is that, whatever it was supposed to provide power to, we don’t have it anymore.

A couple of “alligator clips“, to put onto the wires from the power adaptor. These cost about 50 cents each at the hardware store.

Wire stripper (optional, if you’re handy with scissors)

A screwdriver, that matches the type of screws on your alligator clips.

A small plastic or glass container (something small and disposable, like a small jelly jar or a yogurt cup, is good)

A chunk of copper that will fit easily into your container, and that is thin enough to clip on an alligator clip, and long enough to stick out of the container (a piece of heavy copper wire, or a copper sheet, are both good.  You can get these at any hardware store).  This will be one electrode of your electroplating cell.

A large steel nail that is long enough to stick out of the container.  This will be your second electrode. 

A plastic or wooden stirrer for mixing the solution (a coffee stirrer or a wooden skewer are both good.  Don’t use a metal spoon to stir it, because it will plate copper onto the metal)

A multimeter, either a digital multimeter or an analog multimeter. (It’s optional, you can do the experiment without this, although it does help.)

The Digital Bits Science Lab Experiment:

First, prepare your power supply.  Cut off the end that would normally plug into the piece of electronics, and pull the two strands of wire apart. 

Strip the insulation off of the ends, and put on the alligator clips so that your power supply looks like this:

Put a spoonful of copper sulfate into the container, add water, and stir until the copper sulfate dissolves.

Put in the piece of copper and the nail, with the ends sticking up:

Now, if you have a multimeter, you can check the polarity of your power supply.  Clip the red (+) lead of your multimeter into one of the alligator clips, and the other (-) lead into the other clip.  Set your multimeter to read DC volts, and plug in the power supply.  If you get a positive reading, then you know that the power supply lead connected to your red multimeter lead is the positive lead. If you get a negative reading, swap the power supply leads and try again.

OK, now clip the POSITIVE lead of the power supply to your copper electrode, and the NEGATIVE lead to the steel nail.

If you don’t have a multimeter, just guess which one is which, we’ll be able to figure it out once we turn it on.

Carefully check to make sure that the two electrodes are not touching each other, ideally keep them about an inch apart.

And now, plug in the power supply and watch what happens over a period of about 10 minutes or so.

If the polarity is correct, then you will get metallic copper plating onto the nail, with maybe a small amount of bubbles forming on the nail as well.  Meanwhile your copper electrode will tarnish and turn dark brown or black.  If you leave it running for half an hour or so, you should get a deposit of copper something like this on the nail:

If you have the polarity backwards, then your nail will bubble vigorously, and while there may be a thin film of copper on the surface, it will never build up a significant thickness of copper. 

What’s happening here?

This is an electrolysis reaction.  What we are doing is pumping electrons into one electrode (the nail), while pulling electrons out of the other electrode (the copper).  When you add electrons to a copper sulfate solution, the copper sulfate turns to metallic copper and sulfuric acid. The metallic copper is not soluble in water, so it plates out on the electrode where we are adding electrons.

Meanwhile, at the other electrode we are pulling out electrons.  This makes the metallic copper there react with the sulfuric acid in the solution to make more copper sulfate. 
The overall effect is that copper dissolves from the copper electrode, travels over to the iron electrode, and plates out there as metallic copper.

By adding “smoothing agents” to the solution, it is possible to make the copper plate out as a smooth, shiny metal coating. Similar things can be done with other metals, like gold, silver, zinc, chromium, and nickel.  The metal coatings can be decorative, or they can protect the metal underneath from being corroded, or both.

Description:

A lot of copper mines extract copper from ore by dissolving the copper minerals with sulfuric acid, producing copper sulfate solutions. This lab is one of the ways that they use to convert the copper sulfate into copper metal. Once the copper has been made into metal, it can then be melted down to make copper products like electrical wire.

Equipment needed:

Copper Sulfate. This is one of the most soluble copper compounds, it makes bright blue crystals and dissolves fairly easily in water. You can buy it in hardware stores in several forms, the form I found was Roebic Root Killer (used to clear roots out of sewers and septic systems).

Click the photo to view the larger-sized picture.

Steel wool. Use unsoaped steel wool (the type that is used for sanding varnish), the finer the better.

A small plastic or glass container (something small and disposable, like a yogurt cup, is good)

A plastic or wooden stirrer for mixing the solution (a coffee stirrer or a wooden skewer are both good. Don’t use a metal spoon to stir it, because it will plate copper onto the metal)

The Digital Bits Science Lab Experiment:

Put a spoonful of copper sulfate into the container, add water, and stir until the copper sulfate dissolves.

Tear off a piece of steel wool that is about the same volume as the copper sulfate that you added to the solution:

Put the steel wool into the copper sulfate solution. Use the stirrer to roll it around so that the solution flows through the steel wool. If you use the stirrer to pull the steel wool to the surface of the solution after about a minute, you should see that the steel wool is turning copper colored.

After about 30 minutes, the steel wool should disintegrate into a powder, while the solution changes from blue to green. If you carefully pour off the liquid, you should be able to keep the powder in the bottom.

The powder, which should be reddish-brown, is metallic copper powder. If you dry it and check its conductivity with a multimeter, it should be electrically conductive. If it were just rust from steel wool, it would not conduct electricity after it dries.

What is going on here?

We are starting with copper sulfate in solution (CuSO4), and metallic iron (Fe). It turns out that copper as metal is more stable than iron as metal, so when we put metallic iron into copper sulfate solution, the metal atoms basically switch places:

(Dissolved CuSO4) + (Metallic Fe) ==> (Dissolved FeSO4) + (Metallic Cu)

In the copper mining industry, this process is called “cementation”, and is still used by copper mines that can buy scrap iron cheaply.

See how the electrical conductivity of water changes depending on what is dissolved in it.

Equipment Needed:

A multimeter, either a digital multimeter or an analog multimeter.

Two or three identical containers for water, like drinking glasses or transparent jars

Distilled water. Grocery stores sell bottled distilled water, usually near their bottled drinking water. “Distilled” means it is high-purity water with nothing dissolved in it

Tap water

Baking soda

Sugar

Table salt

A measuring spoon

The Digital Bits Science Lab Experiment:

First, fill one container with distilled water, and set your multimeter to the “ohms” setting for measuring electrical resistance. Touch the multimeter probes together to check that the zero setting is correct. Then, stick the tips of your probes into the water so that the metal part is completely underwater, holding them an inch or so apart. The electrical resistance should be very high.

Next, put some baking soda in the water – about a teaspoon in an 8-ounce glass. Stir it up until the baking soda dissolves, and measure the electrical resistance again. The resistance should be much lower.

Now, fill a series of glasses, with the following

Tap water
Distilled water + 1 teaspoon sugar
Distilled water + 1 teaspoon salt

…and measure the electrical resistance of each. How are they different?

What is going on here?

You should notice that water by itself is not very conductive; that some things (baking soda and salt) make the solution a lot more conductive; while other things (like sugar) do not. What is happening is this: Really pure water is actually an insulator, and does not conduct electricity very well, so it has a high resistance. But, a lot of things that dissolve in water “dissociate”, that is, they break up into electrically charged parts (ions) that can move around. When the ions move, they conduct electricity. Substances that dissolve in water and form ions like this are referred to as “electrolytes”, because they make it possible for water to conduct electricity.

Not all things that dissolve in water are electrolytes, though – the sugar will not make the water very conductive, because sugar dissolves without breaking up into ions. If your sugar did increase the conductivity a bit, it was probably because it had small amounts of some impurities that were electrolytes.

The tap water should have been more conductive than the distilled water, but not as conductive as the water with salt or baking soda dissolved in it. This is because the water out of your tap is not pure, it has minerals like calcium carbonate dissolved in it. Depending on where you live, you could have “hard” water (which has a lot of dissolved minerals in it and is quite conductive), or “soft” water (which has very little dissolved minerals, and can be almost as non-conductive as distilled water).

You can check the conductivities of other liquids, too, like cooking oil, vinegar, or soda pop. Also, see how adding just a little bit of baking soda or salt to water changes the conductivity, compared to adding a large amount.