chemistry, Experiments, Together with sis

MEL Chemistry Experiments: Foil Etching, Magnetizing Magnesium, Metal Contest

In the Foil Etching experiment we had copper burn a whole in the aluminium foil.

This is the reactivity chart from the MEL science website, as you see aluminium is a lot more reactive than copper

As you can see, aluminum Al is much more reactive than copper Cu, but nothing happens when aluminum foil comes into contact with the copper sulfate CuSO4 solution! How come? Unfortunately, it’s all a bit more complicated than it first looks. Being quite an active metal, aluminum Al  reacts with oxygen O2 in the air, forming a very strong film of aluminum oxide Al2O3 on its surface . This film protects the metal from reacting any further.

When you add some sodium chloride NaCl, a vigorous reaction starts as Cl ions are able to compromise the otherwise-strong Al2O3 shield. Once Cu2+ is face-to-face with the aluminum Al itself and not its Al2O3 shield, the reaction can proceed, and quite spectacularly!

the hole in aluminium foil as active aluminium atoms have fled

In the next experiment, we obtained a magnetic substance from two non-magnetic ones, magnesium Mg and iron sulfate FeSO4, via a simple chemical reaction! The Fe2+ from the FeSO4 solution turned into metallic iron Fe on the surface of the magnesium particles, so we ended up with magnesium shavings covered with a thin layer of iron! The picture below shows how the magnesium shavings actually hold a heavy neodymium magnet in the air!

a heavy magnet hanging on the bottom of a glass beaker thanks to electromagnetism

And lastly, we did what MEL Chemistry calls a “Metal Contest”, because here too, three metals (zink, copper and tin) were competing in reactivity. “If you arrange metals from more active to less active, you’ll see that zinc Zn is a more adventurous fellow than tin Sn and copper Cu. That’s why, when you put a zinc rod into a solution containing, say, copper ions Cu2+, the latter are happy to settle inside the comfortable cloud of electrons, forming metallic copper Cu on the surface of the rod. Zn ions Zn2+, in turn, go swimming in the solution. The reaction with the tin chloride SnCl2 solution is essentially the same”, MEL Science website explains.

copper and tin on the surface of the zink rods


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Chemistry Experiments: Polarized light iridizes crystals

Today we have made beautiful rainbow chrystals! Polarized light iridizes sodium thiosulfate crystals, so we made the crystals in between two polarizing films and then observed them through the microscope. In the video, Simon also explains how polarizing film works.

From the scientific description at the MEL Science website: Sodium thiosulfate crystals contain five molecules of water per one unit of sodium thiosulfate Na2S2O3. Interestingly, when heated, the crystals release the water, while sodium thiosulfate dissolves in this water. This solution solidifies rapidly when cooling, forming beautiful crystals. If these crystals are put between polarizing films, they take on an iridescent sheen. This is because the polarizing films only let light with certain characteristics through, and this light in turn “iridizes” the otherwise-colorless sodium thiosulfate crystals.

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MEL Chemistry Experiments: Making Batteries

We did two more experiments a couple days ago: Liquid Wires (creating a simple circuit using graphite and liquid glass, a sodium silicate solution) and making our own Zinc-Carbon Battery, a chemical source of electric current that relies on an oxidation-reduction (redox) reaction between manganese dioxide (MnO2) and zinc (Zn). 

A redox reaction involves the transfer of electrons from one element (the reducer) to another element (the oxidizer).

Our battery is divided into two sections, separated by wadding: one section holds the oxidizer MnO2 and the other contains the reductant Zn. When the crocodile clips are connected to a diode, the circuit is closed and the reaction can begin: electrons start migrating from the zinc section to the manganese section (manganese dioxide mixed with graphite o make it a better conductor). We used ammonium chloride NH4Cl as the electrolyte.

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MEL Chemistry Experiments: Flames and Minerals

Monday was a chemistry day as we went to the post office to fetch our brand new delivery from the MEL Science subscription! We set a record of 6 chemistry experiments in one day! We just couldn’t stop, maybe because all of the experiments involved fire.

We started with the Minerals box. The first experiment was about heating up some semiprecious stones, amethysts (a species of quartz widely used in jewellery). The nature of amethyst’s color is still a mystery: some theories suggest that the color is of organic origin because it changes when amethyst is heated. Our purple amethyst became completely white after we heated it!

Simon watching the solid fuel burn (C6H12N4 – hexamethylenetetramine)
solid fuel C6H12N4 – hexamethylenetetramine – burning with the amethyst wrapped in aluminium foil on top of the flame diffuser
Amethysts in their original color
Amethyst has become white

We also repeated the same experiment with a piece of red coral.

Chemically, coral consists almost entirely of calcium carbonate CaCO3—the same compound chalk is made of (plus the red pigments known as carotenoids). When coral is heated, a strong smell should arise, because of the organic remains left in the skeletal structure. We didn’t really smell much, the coral seemed unchanged after heating:

What we did next was dissolve some malachites! We used NaHSO4 (sodium hydrogen sulfate) as an acid that the mineral would react with and heated the solution up to speed up the process. The big question was: will the malachites dissolve? And will a certain metal come free as a result?

Pieces of malachite in a beaker
The solution turned blue when heated
We added K4[Fe(CN)6], or potassium ferrocyanide, to the solution to detect metal ions. The indicator substance turned brown, which indicates copper ions!

Malachite is a mineral that contains copper Cu! In fact, malachite consists of (CuOH)2CO3 – basic copper carbonate. This compound has been used as a source of pure copper since antiquity, the MEL Science website explains. 

What was left of the malachites

Now it was high time for some fireworks!

This one was our favourite! We performed it many times, just to see the mesmerising green sparkles. All one has to do is dip a stick in paraffine, then in CuSO4 (copper(II) sulfate) for 30 seconds, then in paraffine and (very briefly) in water. This creates a kind of homemade sparklers, like the ones popular on New Year’s Eve, spitting spectacular flashes of green.

What made the flame green is its copper Cu2+ component. Metal ions such as copper ions Cu2+ can emit light of a certain color when heated to high temperatures. Copper emits green, while rubidium Rb creates red and sodium Na creates yellow, and so on. You can create colorful fireworks, but you can also detect which metal is present in a sample by examining the color of the flame.

What else should we burn? Magnesium! Because it lights up so pretty:

From a chemistry perspective, burning is the process of giving electrons to oxygen O in the air, releasing a lot of heat and light. One of the most obvious trends in the periodic table is that the elements on the left side of the table are generally more willing to give electrons away than the ones on the right. But, as we learned from our last experiment called Rocket Fuel, not only oxygen can take electrons from the fuel, in other words, there are other substances that can act as the oxidant (the substance that wants to take electrons from the fuel). If you want your fuel to burn without air, you have to include your own oxidant too. This is how space rockets work.

In our experiment, we mixed the oxidant, calcium nitrate Ca(NO3)2 and the fuel, potassium ferrocyanide K4[Fe(CN)6] that doesn’t burn very well in air (used as fuel for small model rockets and fireworks), and heated them up. When we later set the mix on fire, it didn’t quite produce the effect we had hoped for, the flame went out too quickly to take a good picture.

The oxidant and the fuel
A porridge of oxidant and fuel, calcium nitrate Ca(NO3)2 and potassium ferrocyanide K4[Fe(CN)6]
The very end of the rocket fuel flame burning
chemistry, Experiments, Together with sis

A booming start of the year

We used electrolysis (with sodium hydroxide NaOH solution as the basic medium) to produce oxyhydrogen and extinguished the candle by means of the reaction between hydrogen and oxygen. 

When electrolyzed, water decomposes into two gases: oxygen O2 and hydrogen H2. The end result is twice as much hydrogen as oxygen. Such a mixture of gases is called oxyhydrogen. When a bottle full of oxyhydrogen is placed near a burning candle, the gas ignites immediately and blows out the candle.

Simon also performed two more experiments to purify water (from heavy metals using resin and organic pollutants using activated coal).







chemistry, Experiments, Physics, Together with sis

Chemistry Experiments: Colors (surface active agents and pH indicator)

Our new MEL Chemistry box arrived, containing tons of color fun! We have already tried two experiments. In the Color changing milk experiment, the soap touches the milk creating a very thin film of soap on the milk’s surface and causing the colors to spread along with it, producing a mesmerising effect. Molecules of soap and other similar substances lower the surface tension of different liquids and thus are called surface-active agents (SAA). Simon took it a notch further and created antibubbles that glide on the film of soap:

 

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We thought this one looked like a nuclear explosion:

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The second experiment we did was called Magic Liquid and felt like performing a magic trick: a yellowish liquid poured in five different cups turned five different colors, almost all the colors of the rainbow! The secret was putting a tiny bit of a different chemical substance on the bottom of every cup beforehand. The yellowish stuff was actually Thymol blue, also known as thymolsulfonephthalein (chemical formula C27H30O5S ), a pH indicator, and changed color according the acidity of the substances that were already in the cups. The larger the quantity of protons H+, the higher the acidity of the medium, while the OH ions are responsible for the basic medium:

 

Thymol blue molecule visible on the iPad screen:

We also checked the pH of the substances using indicator standard teststrips:

The pH rainbow:

Schermafbeelding 2018-10-14 om 19.11.46

Simon had already been busy with colors for a few days, revisiting his Magformers collection to build this gorgeous color wheel:

We later repeated the MEL Science demos for Simon and Neva precocious friend:

 

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MEL Chemistry Box number 3: Artificial Snow and growing crystals on a Xmas tree

Our third MEL Science box arrived back in August, when we were on vacation. We have already tried two experiments from the box, both perhaps more suitable for winter. Instant Snow, using sodium polyacrylate (the stuff you can find in diapers):

And growing salt crystals on a paper Christmas tree:

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The second set of MEL Chemistry experiments

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Today we opened our second MEL Chemistry box with two experiments using tin (Sn). We made a tin dendrite and grew a tin hedgehog. Both experiments involved preparing a tin chloride SnCl2 solution (by mixing tin chloride with a sodium bisulfate). In the first experiment, we had electric current flow through the solution (by connecting it to batteries via crocodile clips), so it acted like an electrolyte. A tin reduction reaction took place: Sn2+(solution) + 2e→ Sn(solid)

The tin dendrite grows in the direction that the electric current flows through the solution; from one clip towards the other:

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In the second experiment, we simply dropped a piece of zinc into the tin chloride solution. What happened as a result was a substitution reaction: some zinc dissolved into the solution, while tin precipitated on the surface of the zinc pellet in the form of lovely needles:

SnCl2 + Zn → Sn + ZnCl2

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Our first MEL Chemistry set has arrived!

We have received our first MEL Chemistry box, something the kids were really impatient to start. And guess what, finally something to be proud of being a Russian from St.Petersburg – that’s where MEL Science kits are actually being made! It’s been a while since I have seen a “Made in Russia” on anything awesome.

The first two experiments we tried today were part of the Artificial Sea Set: Chemical Seaweed and Chemical Jellyfish. They both involved working with metal salts (sulphates) and watching them react with different solutions. The time lapse video above shows the seaweeds “growing”: “Metal salts gradually dissolve and react with the potassium hexacyanoferrate(II). Insoluble copper, iron and zinc compounds form. These don’t just precipitate out but form “bubbles” because of the osmotic pressure. The fancy chemical seaweed grows from these bubbles”.

It was fun to watch the metal salts change colours: iron turned bright blue and blue copper sulphate turned brownish red!

The funny little things in the petri dish are the “jellyfish” we made as a finishing touch to our artificial sea. We created theses by firing metal salt solutions into sodium silicate (liquid glass). “An ion exchange reaction occurs between the sodium silicate and the metal salts. As a result, insoluble metal silicates form. These resemble jellyfish!”

Metal salts starting to grow in potassium hexacyanoferrate:

Unboxing the first kit:

Busy with the experiment(s):

We also dived into the MEL Chemistry app that allows you to see all the molecules of the reagents involved in 3D.