Wanted Dead and Alive

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Happy Birthday Dorthy Mary Crowfoot Hodgkin

Dorothy Mary Crowfoot Hodgkin, born 12 May 1910, was a British founder of protein crystallography. She pioneered the technique of X-ray crystallography, a method used to determine the three dimensional structures of molecules. Among her most influential discoveries are the determination of the structure of penicillin, insulin, and vitamin B12 for which she was awarded the Nobel Prize in Chemistry. In 1969, after 35 years of work, Hodgkin was able to decipher the structure of insulin. She is regarded as one of the foremost scientists in the field of X-ray crystallography of natural molecules.

Eat. Sleep. Chemistry.

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Test Tube Science: Fizzle Fizzle

Awhile ago I sent out some test tubes and pipettes to my nieces and nephews.  I said that I would be posting some experiments that you could do with them.  Here is the first experiment.

This is a fun way to start using your test tubes and pipets.  To run this experiment place about 1mL of sodium bicarbonate (baking soda) in the bottom of a test tube. Now fill your pipette with 5% acetic acid (white vinegar) and squirt it into the test tube. Be prepared for this to overflow the test tube, it is part of the fun. Repeat the addition of acid until no more bubbling occurs. The first time I did this with my son he was about 22 months old.  I asked him to put the tube by his face and asked if he could feel the fizzing.  He then took to calling it fizzle fizzle and often asked for it by name.

Try this again but instead of adding all of the baking soda at once place half of the soda in and then place a drop of food coloring in the test tube taking care to have it drop in the center of the baking soda.  Then add the rest of the baking soda.  After the second or third addition of vinegar the foam will turn the color of the dye much to the delight of the young scientist.  

This activity is not just for the youngest scientists.  Because carbon dioxide is more dense than air the test tube will stay filled with carbon dioxide.  This can then be poured over a match extinguishing the flame.  This shows  both the greater density of carbon dioxide and the need of oxygen during combustion.

Another variation on the sodium bicarbonate acetic acid theme is to make rockets out of film canisters.  Place some baking soda in the film canister next add some vinegar and quickly snap on the lid.  Invert the canister so that the lid is on the table and wait.  In a short time the canister will pop a few feet into the air.  I've done this a few time with cub scouts and they love the excitement of not knowing when the rocket will launch.

The last suggestion for baking soda and vinegar is a lab fire extinguisher.  Some old fire extinguishers had an aqueous solution of baking soda  and a small bottle of sulfuric acid in them.  When the fire extinguisher was inverted the acid would react with the baking soda and produce carbon dioxide.  The carbon dioxide would then force the water out and it could be used to extinguish the fire.  You can build your own lab fire extinguisher as shown in this illustration from the Golden Book of Chemistry.

Writing With Amino Acids

Most of the letters in the alphabet have been used in the standard abbreviations for the 20 proteinogenic amino acids.  If you add in a few other amino acids and some uncertainties all of the letters are accounted for.  This means you can code words into peptides.  I'll show a few examples below:

STAY

 Each amino acid starts with the nitrogen so in this image you can see there are four amino acids (serine, threonine, alanine, and tyrosine) one for each letter in "Stay."

COSBY

Notice the R in the diagram (just above the last NH) comes from "B" which indicates either asparagine or aspartic acid.  The R indicates where asparagine and aspartic acid are different.

AHLSTROM

SUMMERSTAY

Can you identify the already seen "Stay" portion?

HOMER

So now you can pass notes during chemistry class.

British Vs American Elements

I wrote earlier about the elements using Google's ngram service and here I present some comparisons of british vs American spellings of a couple of elements.

Aluminium vs Aluminum

Caesium vs Cesium

As you can see the British spelling is higher to begin with but then falls to the American spelling.

Ngram Chemistry

I was playing around with one of Google's toys and my thoughts turned to chemistry.  I then thought that I'd look to see how each group broke down.  I started with group 1

You can see hydrogen starting in the 1790 after Cavendish realized it was an element.  From this graph we would assume that sodium and potassium were discovered around 1810 and sure enough Davy isolated both of them in 1807.

Group 2

Radium is the interesting one here where we can clearly see its discovery in 1898.

Group 3-Group 12

What I'd like to know is what happened to silver between 1790 and 1810.

Group 13

Look at 1890. The Hall-Héroult process was put into use in about 1890.
Group 14

Group 15

Group 16

 Group 17

Group 18

Rare Earths

 

 

I then took the most used element of each group and pitted them against each other as a battle royal of the elements.

Not surprisingly gold, lead, and iron are the top three with first prise going to iron.

Carbonated Fruit

My Mother-in-law gave me a really fun toy awhile ago, an iSi cream whipper.  To use it you place some cream into the container and then screw on a cartridge filled with N₂O, shake it up, stick it in the refrigerator, and wait awhile.  While you wait the N₂O dissolves into the cream.  You put it in the refrigerator because the solubility of gases in liquids, unlike most solids in liquids, increases as the temperature decreases.  When you pull the trigger the pressure in the container pushes the cream out, when the cream hits ambient pressure the dissolved gas comes out very quickly (like when you open a soda bottle and some of the carbon dioxide comes out of the soda).  This makes the cream become frothy or whipped.  But that's not what this post is about. This post is about carbonated fruit.

The charger is also able to use a CO₂ cartridge.  To make the fruit I cut up some grapes (to increase the gas permeable membrane) and used Mandarin oranges.  I placed them in the charger and charged it with one CO₂ cartridge.  After about three hours I vented the container with the fruit in it and opened the container.  The fruit was delicious.  It tastes marvelous. The carbonation really tickles the tongue but the fruit is still just as sweet as it ever was.  When we did it again later we added sliced strawberries to the mix and they were great too.

Look at how the carbonation has made them swell.  You  can see the bubbles coming out of the fruit.

What is it?

Here are a few more SEM pictures.

These are from a fly I caught at our house.

A spider fang.  I like how you can see the hole through which it injects the venom.

This is the wispy part of a dandelion seed.  Notice how the shafts are hollow.

Happy Birthday to Me

I recently had my birthday.  My parents sent me some money and I used it to buy something I've wanted for a long time.  I've wanted a thermometer that can be plugged into my computer for a long time.  I have also been gaining an interest in electronics.  I have a simple analog voltmeter but it doesn't do anything else.  So I purchased a multimeter that also has a thermocouple that can plug into my computer via an infrared link.  The infrared link protects my computer from the electronics in the multimeter or the things I attach it to.  I put the thermocouple into a test tube full of water and dropped it into the deep freezer.  I had it sample the temperature every two seconds and recorded the graph below.

Some of the cool things to notice are the supercooling of the water before freezing.  The water cooled to -1.1 degrees before it started to freeze (~1000s) at which point it warmed up to 0.6 degrees as the water released energy as it starts to crystallize (the heat of crystallization for water is ~6 kJ/mol) .   It then cooled to 0 and stayed there for the next 25 minutes until all of the water had frozen and then it began to cool the ice.

Thanks for the great toy Mom and Dad!