Introducing Chemistry with Balloons, Slime, and Lava Lamps

An Essay By Hannah D. // 6/15/2017

This is another science lesson, in the same library as the one described in "Using Microcosms as an Introduction to Ecology." Kids really love balloons, and they really love slime! Needless to say, it was an exciting afternoon.

Materials
You can find these experiments easily on the internet. The lava lamp is just a mix of vegetable oil, water, and food coloring. The slime recipe we used was made from borax, Elmer's glue, and water.

It helps to have a diagram of an atom - protons, neutrons, and electrons all visible. It's also nice to have some sort of modeling kit for showing molecules made from atoms and bonds. You can purchase a kit that allows you to build molecules this way, or you can just make molecules beforehand with different colored clay balls attached with toothpicks.

Lesson
Experiment #1: Balloons & Static Electricity
From a physicist’s perspective, there are two things in the universe: matter and energy. Energy is light, heat, things like that. Matter, however, is what makes up all the “stuff” around us. And matter is made up of atoms.

Atoms are very tiny, impossible for us to see – even with a microscope. They are made up of protons, neutrons, and electrons. Neutrons have no electric charge, but protons have a positive electric charge, and electrons have a negative charge.

Atoms are identified by the number of protons they have. On your periodic tables, you can find Oxygen as number 16. That means that oxygen atoms have 16 protons. Oxygen is in the air we breathe. Another atom is carbon, number 6 on your table. Carbon makes up the graphite in pencils, and it also makes up diamonds. Computers and cellphones have silicon chips in them; silicon is on the periodic table and has 14 protons, so it’s number 14. Other atoms you can find include helium (you may have had helium balloons at parties), aluminum (in aluminum foil), gold (in Mom’s jewelry), and neon (in the light-up “Open” signs seen in store windows).

Atoms usually keep the same number of protons at all times, since the protons are packed together tightly in the center of the atom. The electrons, however, spin around them, so atoms can gain or lose electrons fairly easily. When atoms change their number of electrons, they become electrically charged.

We can watch this at work with our balloons. Everyone take a balloon and rub it in your hair. When you do this, the balloon is picking up stray electrons, so it gains a negative charge. Your hair loses electrons this way, so it is now positively charged. Your hair is then attracted to the balloons and stands up so that it can reach them. This is because opposite charges attract each other.

Now take two balloons and charge them both in your hair. Without letting them spin away from each other, try to bring them close together. Can you feel them repel each other? That is because similar charges repel each other. Both of the balloons picked up a negative charge from your hair, so they try to keep away from each other.

Now let’s scatter some rice krispies on the desk. When we charge our balloons up, they want to get rid of all their extra electrons. When we bring our balloons over the rice krispies, the balloons see them as a place to discharge their extra electrons on. This induces a positive charge in the rice krispies, and the krispies “dance” to get closer to the balloons.

So, we know that atoms can gain or lose electrons to develop an electric charge. But let’s take a closer look at our periodic tables. If all matter – everything around us – is made up of atoms, then where is wood on the periodic table? What about sugar? Water? Plastic? Oil? Well, atoms can also share their electrons with other atoms. When this happens, an electric bond is formed. Atoms bond together to create molecules.

I have here models of two different types of atoms. Right here is an organic compound (I made butane, C4H10). Oil is an organic compound, and that means it is kind of like this model - it contains a lot of hydrogens and carbons. These larger black spheres are the carbon atoms, the small white ones are the hydrogens, and the grey rods between them are the bonds. If I hold this molecule at the center, you can see that it’s pretty easily balanced in weight. This molecule shares its electrons evenly.

This, however, is a model of a water molecule. The small white spheres are still hydrogens, but the larger red one is an oxygen atom. It is not as balanced as the carbon-hydrogen molecule over there. In fact, oxygen is quite a bit bigger and stronger than the hydrogens, and there is nothing to balance it out. So the oxygen actually steals more than its fair share of electrons. That means that hydrogens get a bit of a positive charge, and the oxygen gets a little bit of a negative charge.

So water molecules have some innate charges to them, which means that water can interact with our charged balloons! Let’s go over to the sink and see what happens when our charged balloons are brought close to a thin stream of water.

The water bends towards the balloon! This occurs because of the charges we’ve seen in the water molecule. If I had a thin stream of vegetable oil, it would not respond at all to my balloons, since vegetable oil has evenly balanced electrons and no net electric charge.

Experiment #2: Making "Lava Lamps" with Polar Liquids
When molecules like water have an electric charge, we call them polar molecules. When molecules have no charge, like the oil, we call them nonpolar. Polar molecules can mix with polar molecules. And nonpolar molecules can mix with nonpolar ones. But you cannot mix polar and nonpolar molecules together.

That’s because when water and oil are mixed together, water’s electric charges will ensure that water will always be more attracted to itself than it will be to the oil. Let me fill this glass up to the brim with water – see how the water curves up on the top instead of spilling over the sides? Water's charge gives it a property called surface tension. Each water molecule’s hydrogen atoms are attracted to other water molecule’s oxygen atoms, since positive and negative charges attract each other. Since water likes itself so much, it doesn’t want to mix with oil - it wants to stay with other water molecules.

Let’s see how that works with these water bottles. I’ve filled them half way with water; now let’s pour some vegetable inside too. The oil doesn’t mix with the water, but instead floats on top. Vegetable oil sits on top of the water because it has a lighter weight. As scientists, we say that oil has less density than water does.

Now, let’s try to make things interesting. Let’s pick some colors to play with and drop in into our bottles. The food dyes slip right through the vegetable oil and mix in with the water – that probably indicates that food dye is a polar molecule. It would rather mix with water than with vegetable oil.

Here are some alka seltzer tablets. When you drop these in water, a chemical reaction occurs that releases a gas, and you get lots of bubbles. The bubbles should help to stir things up inside, so let’s see if it can get oil and water to mix.

After the bubbles have died down a bit, I can put the lid tightly on my water bottles and try mixing them together myself. Shake as I will, I cannot get water and oil to mix. I have, however, achieved this bubbly mess you see here. It may look like the oil and water have mixed together, but we’ll let it sit for a few seconds. What I have here is basically a lot like salad dressing – you have to shake it before using it, but it separates again as soon as you put it back on the shelf. If you look carefully, you’ll see that there’s already a layer of a paler color forming on top of our bottle. That’s the oil, and the water is dripping downwards to the bottom again. Thus, we know that the oil and water didn't actually mix together - they separate away from each other as soon as I stop shaking them up.

Do you ever have to clean the dishes in the kitchen? If you’re trying to wash a particularly greasy dish, you will never get it clean if you just run water over it. That’s because water and grease (which is a nonpolar fat, like oil) can’t mix. Add some soap, however, and you can break the grease up easily. Why is that?

Well, soap molecules are actually really big, complicated molecules that have two parts to them. One part is polar, and the other is nonpolar. The polar part mixes with the water, and the nonpolar part mixes with the grease. This solves the problem and allows the greasy stuff to wash right away! So next time you’ve got to clean up the dishes after dinner, you are really getting the chance to watch chemistry work for you. 

Experiment #3: Making Slime
So, we have atoms. We have atoms that gain or lose electrons to get an electric charge. And we have atoms that share electrons to make molecules.

Molecules can also break their bonds and re-share their electrons in new ways to make new molecules. We call this a chemical reaction. There are lots of different types of chemical reactions, but today we are going to work with a kind called polymerization.

Polymerization takes one type of carbon molecule – like this carbon-and-hydrogen molecule model we have here – and strings them together to make a really long molecule of carbons and hydrogens. We call this molecule a “polymer” – “poly” means “many.”

This type of reaction is a favorite of Synthetic Organic Chemists. Organic chemistry works with carbon-based molecules. Synthetic just means that it’s made in a lab instead of found in nature. Synthetic Organic Chemistry is what gives us long carbon molecules like polyester and the many different types of plastic. As the small carbon molecules link into longer and longer carbon chains, they form molecules that get ooier and gooier until you get a slime.

We can make that slime now, making you all Synthetic Organic Chemists. :)

Comments

Love it!

I LOVE science experiments!! These are super simple and yet really fun. :)

Sarah Liz | Mon, 06/19/2017

"Knowledge is knowing that a tomato is a fruit; wisdom is not putting it in a fruit salad." ~ Anonymous

Thanks. :) The kids seemed to

Thanks. :) The kids seemed to enjoy them immensely too.

Hannah D. | Mon, 06/19/2017

"Reason itself is a matter of faith. It is an act of faith to assert that our thoughts have any relation to reality at all." - G. K. Chesterton