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.

chemistry, Experiments, Together with sis

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
Biology, chemistry, Math Riddles, Milestones, Murderous Maths, Physics

Bayes’ Theorem

Bayes’s Theorem calculates the probability of an event based upon the conditions that might be relevant to the event and is widely used to test the precision of medical tests and drugs efficacy.

Simon explains Bayes’ Theorem to Dad. To illustrate the theorem, he loves using the math riddle he first saw on the Veritasium channel, about someone getting positive results on a rare disease test: The test has a precision rate of 99% and it is also known that the disease occurrence rate is 1/1000. What is the probability that the person tested positively really has the disease? (Answer: 11/1000 or 9%).

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, Crafty, Experiments, Group, Museum Time, Notes on everyday life, Physics, Together with sis

Science Day in Belgium

Yesterday we attended one of the hundreds of Science Days venues open for free all over Belgium. Simon particularly enjoyed chemistry demos, even though he was disappointed that some companies showing their inventions didn’t want to share the actual formulas behind the tricks.

The simple non-newtonian fluid remains a favourite.

Making your own bath bombs.

Simon dazzled by how insulator foam (polyurethane) is produced as the result of a reaction between two highly viscous substances, an isocyanate and a polyol (polyether). Another fascinating thing about this demo was that the tool mixing the two ingredients actually employed magnets!

A workshop explaining why ships don’t sink and if they do, why:

Exploring 3D printing:

Programmable spheres:

Heat indicator (material changing color depending on water temperature):

The good old baking soda and vinegar demo revisited:

Biology, chemistry, Crafty, Geometry Joys, Milestones, Notes on everyday life, Physics, Together with sis

Molecules

Simon is seriously enjoying his new Molymod chemistry modeling sets and has been obsessing about which set contains what atoms and bonds.

Alcohol (Ethanol):

Hurray! We have just built 7,333333333333 x 10^-9 of the human DNA:

Glucose

Some like the football, Simon plays with the buckyball, or Buckminsterfullerine, made up of 60 carbon atoms: