Hot ice~

       This week I gonna share a experiment called "hot ice" with you guys~ Let's see the video first~

Wonder what is happening? The experiment just shows an interesting feature of superstation (過飽和). The colorless solution is actually water supersaturated with sodium acetate (醋酸鈉). Most of you probably have heard of supersaturation, which means that there are more solutes (in this case, sodium acetate) than normal in the solvent. Supersaturated solution is not thermodynamically stable but there is no proper way for it to transform into the more stable crystal phase since the energy barrier is too high.


However, once you put a “seed” (or nucleus, 晶種) into a supersaturated solution, the crystal will form rapidly because the seed has decrease the energy barrier considerably (btw this phenomenon is called heterogeneous nucleation).  

  What’s more, the reaction is exothermic—it generates a large amount of heat at the same time. So that’s why it is called “hot ice”! Here’s a video about how hot it could be. Though hilarious, you should take it seriously! (I have no idea why he wanted to put his hand inside it@@ why not just put a thermometer......)

     Never try to do that stupid thing at home, but here's something you can try. Some hand warmers  just make use of this phenomenon. You are supposed to “crush” them before use and them can be reused by putting them into hot water. Interestingly, the crush you do is actually providing a seed for the crystal to grow. By using these hand warmer, you can directly feel the heat produced when forming sodium acetate crystal, in  a more gentle way of course!

reference:

1.http://www.amazingrust.com/Experiments/how_to/Hot-Ice.html

2.https://en.wikipedia.org/wiki/Nucleation

3.https://en.wikipedia.org/wiki/Sodium_acetate

sandwich and hamburger molecule

  

  I think there are too much organic compounds in the previous posts; though organic compounds indeed have a much greater variety and flexibility in structure, inorganic compounds do also have something to show! So this week I would like to introduce some classes of inorganic compounds with interesting structures. The first class is sandwich compound, they have structure like this:

   The dash lines between the metal and the ring up and down are not actually chemical bonds, they are  just simplified symbols to represent a special type of coordination bond. 

   Still one thing worth mentioning is that though the “bread” of the sandwiches are different (pentagon, hexagon, octagon…), they are all aromatic (芳香). This property stabilizes the overall compound structure.

   If you have no idea what previous sentences are talking about, don't be afraid, just appreciate their structure~

Of course there is “half sandwich” compound, which is also called "piano stool" compound due to their structure. Here’s one example:

And this is piano stool haha:

    What’s more, there is "mutlidecker sandwich" compound, just like big mac! Take a look at the structure:

  However, there are more classes of compound, as the image below shows, and I only mention a narrow range of them today! Hope you can have a deeper insight into molecular structure after reading my post~

Explosive experiment

    This week I want to introduce something sensational and explosive~

The first experiment is the chemical volcano. Literally, it is a experiment that have a volcano-like product. Let’s check out the video first:

 

  The reaction is the heat decomposition of ammonium dichromate [(NH₄)₂Cr₂O₇], and during the decomposition, it will produce lots of ashy Cr₂O₃ and accumulate into a mountain. The total reaction equation is (NH₄)₂Cr₂O₇ → Cr₂O₃ + 4 H₂O + N₂

  

  Another similar reaction is the Pharaoh’s serpent (法老之蛇). It is the decomposition of Mercury(II) thiocyanate, while in this reaction, the decomposed product resembling a snake rather than a volcano.

The reaction can be described as below:

2Hg(SCN)₂ → 2HgS + CS₂ + C₃N₄

HgS + O₂ → Hg + SO₂

2C₃N₄ → 3(CN)₂ + N₂

CS₂ + 3O₂ → CO₂ + 2SO₂

Here’s the video:

*Warning: the experiment would be a little bit disgusting…

   Last one will be the experiment of dehydration of carbohydrate. Simply, the “de”hydration of carbo”hydrate” will produce “carbon”! Sulfuric acid (H₂SO₄) is often used as a strong dehydrating agent, so we can see black carbon forms after we mix the sugar (carbohydrate, C₆H₁₂O₆) with sulfuric acid. The reaction equation is C₆H₁₂O₆ → 6C + 6H₂O

Here’s the video:

Reference:

1.      http://chemistry.about.com/cs/demonstrations/a/aa033003a.htm

2.      http://chemistry.about.com/od/fireworksprojects/a/pharaohs-snakes.htm    

Molecules in daily life

  Chemistry is everywhere, and it is an essential part of our world. So let’s look up some molecules in our daily lives!

  Here come the molecules in chocolate—phenylethylamine, tryptophan, and theobromine. Scientists used to believe that phenylethylamine and tryptophan make us feeling good after having some chocolate, however, latest research suggested that it could only be a placebo effect since these compounds would undergo metabolism(代謝) when we consume them. Theobromine is harmful to dogs, so never let your dog try chocolate!

  There are countless kinds of smell in our lives, have you ever wonder what molecules are interacting with your nose? Let’s consider the scent of flowers first. Here’s a list of compounds behind the smell of flowers:

  Another interesting topic is the smell of books. The distinct aroma of new books comes from the inks, papers, and adhesives while that of old books comes from oxidation products of polymers which make up the papers.

  Do you remember the refreshing smell after rain? It is caused by the compound geosmin and volatile fat molecules, as shown below. By contrast, the beyond-description smell before rain is arisen from ozone.

    All information is retrieved from http://www.compoundchem.com/ .You can also search “compound interest” on FB to follow their pages. The website talk about the chemistry behind everything in our lives, and it is really worth reading!