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.

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.

“Your Multimeter and You”: use a multimeter to measure electrical resistance of things, including yourself.

What is a multimeter? Multimeters are instruments to measure several different things, including electrical conductivity, electrical current, and electrical voltage. You can get very cheap ones (see the photo below). You’ll find them at hardware stores for approximately $10 – $20, or you can spend tens, hundreds, or even thousands of dollars for really high-end professional models.  I recommend one of the cheap ones. These can either have a needle and dial reading like the one shown here (analog multimeters) or a numerical display (digital multimeters).

Equipment Needed:

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

You

A metal object, like a coin

A piece of plastic, wood, or glass

A pencil with the eraser pulled off of one end so that you can see the pencil lead

The Digital Bits Science Lab Experiment:

A multimeter has many different settings, the one we are going to use is one of the ones marked “R” (for resistance) or “Ohms”:

This setting is used to measure how easily electricity flows through an object. What the multimeter does is this: it has a battery inside that is connected to the probes.  When you touch the probes to an object, electricity flows from the battery through the object.  If a lot of electricity flows, that means the object has very little electrical resistance, while if hardly any electricity flows, that means the object has very high electrical resistance. The multimeter measures the electrical current flow, and uses this to calculate the resistance of the object in units called “Ohms”.

So, turn the settings selector on your multimeter to measure resistance. First, check the calibration of your multimeter.  With the probes not touching each other, the reading should be “infinite resistance”, meaning no electricity is flowing. When you touch the probes together, the multimeter should read zero resistance, meaning that the current is flowing through the probes as quickly and easily as possible.

Now, we are ready to make some measurements. 

First, check a metal object: the resistance should be very close to zero ohms because metals are very good conductors of electricity.

Next, plastic or wood: the resistance should be extremely high, because these are all very bad conductors of electricity (insulators).

Now try the pencil: touch the multimeter probes to the lead on each end of the pencil.  You should get a reading of somewhere around 10 to 100 ohms. This means that the pencil lead (graphite) will conduct electricity, but that it is not as good of a conductor as most metals.

Finally, try yourself: grab hold of one probe in each hand, and see what your resistance is (don’t worry, the battery in the multimeter is not strong enough to give you a shock).  If your hands are dry, you will probably have nearly infinite resistance.  If your hands are sweaty, or if you lick your fingertips before taking hold of the probe, you should have
a resistance somewhere around 50,000 ohms.  If you touch the probes to your tongue, the resistance should be much lower.

So, this means that while your body has a lot of resistance, it has less resistance than an insulator like a piece of wood.  This is why you can get electrically shocked (because electricity can flow through your body), and why electrical appliances near water are a bad thing (because if you are wet, you have a lot less electrical resistance than if you are
dry).

This experiment shows how water can conduct and absorb heat.

Equipment needed:

Water

Balloons

A lit candle

The Digital Bits Science Lab Experiment:

Blow up a balloon. Hold it over the lit candle. Boom! The balloon explodes! The lit candle heated the balloon, weakened and melted it, and the balloon exploded.

Now take another balloon, and fill it halfway with water.

Hold that same balloon over the candle. Do you think the balloon will explode, splashing water everywhere?

Nope.

You can have the candle flame actually touch the balloon, and the balloon won’t break!

The water in the balloon is absorbing the heat from the candle. The balloon conducts heat very well, so the candle flame transfers to the water without harming the balloon.