Coligative References

Colligative Properties


As always I say: “Chemistry surprises you with the simplest things that you used to do in life”.


   Now, I am going to ask you: Have you ever seen people adding salt to ice in an ice cream maker? Have you ever traveled to countries where the snow is falling and in the next day people sprinkle salt on icy roads?
     The reason that people do this is not an alien behavior; they do because salt lowers the temperature at which water freezes. So, the question is how chemistry explains this? The temperature enough to make water harden into ice is 32 degrees Fahrenheit or 0 degrees Celsius. But when you sprinkle salt on ice, salt which is a compound called sodium chloride, interrupts the freezing process of the water. Some of the ice will melt because the salt pulls some water away from its crystal form (ice) and also mixes with the thin layer of water on top of the ice. This creates more saltwater, which will melt more ice. The dissolved salt will also prevent the melted ice (now water) from refreezing. Molecularly, salt slows the action of water molecules trying to join together into crystals to form ice or snow. Now, the temperature to form ice again is about -10°C.
     For example: on a winter road, the salt allows the ice to melt when the ambient temperature is below freezing. In other words, for the mixture of salt and ice or salt and water, it has to be colder than 0° C or 32° F to freeze. The depression of freezing point of water by salt is an example of the colligative properties of solutions.

The colligative properties are: freezing point depression, boiling point elevation, osmotic pressure and vapor pressure lowering. To understand how these properties work I am going to explain briefly the concept of solution.
     In general, a solution is a homogeneous mixture composed of a solute and solvent. The solute is the minority component which in this case is the salt and the solvent is the majority component which in this case is the water. The colligative properties depend on the number of particles (solute) that were dissolved in solution (that contain solvent). Basically, the more salt (solute) is added to the same amount of water (solvent), the lower its freezing point will be.


Let’s use chemistry in our favor to can go out in winter without the snow covering us at all.


I want to know others chemistry tricks that you use to combat the snow?
Let me know which are yours and remember see the video and photo below. Also, if you want to read more about colligative properties go to the references.


Thanks,

-Stephanie

References

1) https://www.highlightskids.com/science-questions/how-does-salt-melt-ice-and-snow

2) Tro, N. J.; “Chemistry: A Molecular Approach”, 3rd ed., Pearson Prentice Hall: New Jersey, 2014.

Chemiluminescence

Chemiluminescence

Yes, I am sure that you read the title twice because you cannot pronounce it in the first try. Now, you are smiling because what I said before is true. Do not worry I had to pronounce it almost 25 times to explain to my colleagues what that is?  Let’s talk about luminescence in Chemistry or best known as Chemiluminescence.

     Everyone at once has seen glowsticks in a night club, fireflies or beautiful jellyfishes glistening, but from where comes the illumination of those things or species? The answer is simple, is because the Chemiluminescence. This is the production of light from a chemical reaction. Two chemicals react to form an intermediate in excited state (high energy), which is de-energized releasing some of its energy as photons of light.

     For example: Luminescent reactions of fireflies use ATP (adenosine triphosphate) as a source of energy. The structure of molecules that produce the light in fireflies varies from species to species, but they are generically called luciferins. When fireflies glow, the luciferin is oxidized to produce an excited complex, which falls back to the ground state, releasing a photon of light. That light is what we see at night into the woods.

     Fluorescent jellyfish are probably the epitome of chemiluminescence and bioluminescence sophistication. They have a protein capable of receive high-energy light (typically in the range of UV) called GFP (Green Fluorescence Protein) that emits fluorescence in the range of green light (Although biotechnological modifications have gotten proteins that emit virtually the entire visible spectrum). Jellyfish are not nearly the only bioluminescence’s marine life, it is believed that more than 90% of animal species average and abyssal ocean portion emit some kind of bioluminescence. Also, there have been a series of experiments investigating aequorin, a protein found in certain jellyfishes, which produces blue light in the presence of calcium and therefore can be used in molecular biology to measure calcium levels in cells.   

     Other way to see chemiluminescence… I think that everyone in a particular moment has seen Action or Police movies which have scenes where a forensic scientist investigates if in a zone there is blood present. And he or she does it using an apparatus with light that show in seconds the blood stains. Basically, in real life forensic scientists use reactions of luminol to detect blood at the crime scene. A mixture of luminol in a dilute solution of hydrogen peroxide is applied in the area where they suspect that is the blood. The iron in the hemoglobin of blood accelerates the reaction and when the room is dark and if blood is present, a blue glow, lasting 30 seconds is observed. Forensic investigators can record the glow by using photographic film, which can be used as evidence in court of blood in the scene.

Some scientists have proposed other ideas for utilizing chemiluminescence in the future; from detect important ions in biological processes to have fluorescent fishes as decoration. What other alternatives you think is useful for us, based in this natural phenomenon and the concept of chemiluminescence?

Let me know.

Have a great week!!

-Stephanie

References:

https://tallcute.wordpress.com/2008/01/15/colores-vivos-de-la-naturaleza-a-la-biotecnologia/

http://www.scienceinschool.org/node/2355

http://www.bbc.com/mundo/noticias/2013/01/130116_bioluminiscencia_naturaleza_produce_luz

Images from:

http://www.slideshare.net/kendonsmith/electron-configurations-notes

http://bioloblogeo.blogspot.com/2015/03/como-se-iluminan-las-luciernagas.html

http://dciencia.es/c-s-i-dciencia-el-luminol/

http://slickzine.com/nature/stunning-jelly-fish-photography/

Magic Chemistries

Magic Chemistries

As I said before my purpose with this blog is not only share information that you cannot understand or you do not like it or bores you. I want to catch your attention with chemistry; science is not boring at all. Everyone in a moment dreams to have super powers or abilities to do magic. Now, I have to tell you: that dream IS POSSIBLE WITH CHEMISTRY!!

Chemists use reactions to produce different compounds. The majority of magic chemistries are related to mix the correct things to have the most surprising products. There is a many types of chemical reactions that chemists do but the most used to magic chemistries are: oxidation-reduction, combustion, synthesis, decomposition, substitution or single replacement or metathesis. Doing these reactions correctly we can produce: invisible inks, substances that change mysteriously of color, water that muddies blowing air, an egg fry without oil and heat, lemonade that turns into wine, white sugar becomes in black coal. It looks like magic, but it is the product of chemistry and its reactions. And that is why I call it magic chemistries.

You can use chemistry in your favor to surprise other persons during a magic show or to have fun with your family or friends or use it in science projects to catch the attention of your public.

Below are the scientific or chemical concepts behind two chemical tricks that you can do carefully and with the consent of your parents:

   1)    Set money on fire and watch it burn out without damaging the bill.

A combustion reaction occurs between alcohol and oxygen, producing heat and light (energy) and carbon dioxide and water.

C₂H₅OH + 4 O₂ -> 2 CO₂ + 3 H₂O + energy

When the bill is soaked an alcohol-water solution, the alcohol has a high vapor pressure and is mainly on the outside of the material (a bill is more like fabric than paper, which is nice, if you've ever accidentally washed one). When the bill is lit, the alcohol is what actually burns. The temperature at which the alcohol burns is not high enough to evaporate the water, which has a high specific heat, so the bill remains wet and isn't able to catch fire on its own. After the alcohol has burned, the flame goes out, leaving a slightly damp dollar bill.

Materials: dollar bill, tongs, a lighter, salt, solution of 50% alcohol and 50% water (you can mix 95% alcohol with water in a 1:1 ratio, if desired)

Procedure:

   1.     Prepare the alcohol and water solution. You can mix 50 ml of water with 50 ml of 95-100% alcohol.

   2.     Add a pinch salt or other colorant to the alcohol/water solution, to help produce a visible flame.

   3.     Soak a dollar bill in the alcohol/water solution so that it is thoroughly wet.

   4.     Use tongs to pick up the bill. Allow any excess liquid to drain. Move the damp bill away from the alcohol-water solution.

   5.     Light the bill on fire and allow it to burn until the flame goes out.

   2)    Smoking fingers.

Phosphorus is a chemical element that can take several forms, called allotropes. The type of phosphorus in the striker of match boxes is red phosphorus. When you burn the striker, the phosphorus is vaporized and condenses into a solid onto the cool metal surface. This is white phosphorus. The element has not changed identify just the structural arrangement of the atoms. Rubbing your fingers together produces enough heat from friction to vaporize the phosphorus into what appears to be smoke.

White phosphorus readily reacts with oxygen in air to form a flammable compound. Because of this, one of the earliest uses of the purified element was to make matches. The early phosphorus-based matches were dangerous, containing enough phosphorus to poison a person. Modern matches are called "safety" matches because they don't use highly toxic chemicals. The smoking fingers trick used to be a popular school science demonstration. It is not performed much anymore because of concerns about the risk from the phosphorus, but if you do the trick infrequently, the dose of phosphorus is small. You can lessen the exposure by wearing thin, disposable gloves and taking care not to breathe the vapor.

Materials: matchbox of safety matches, cold water faucet or chilled pan, scissors, lighter

Procedure:

    1.     Cut out the striker portion of a matchbox from a box of safety matches. Trim off any paper around the striker.

    2.     Fold the striker in half, striker-sides facing each other.

    3.     Set the folded striker on top of the running cold water faucet or a refrigerated metal pan.

    4.     Use a lighter to set fire to the striker. Ignite both ends. Then run the lighter along the length of the folded striker. It won't burn to ash, which is fine.

    5.     Discard the burned striker.

6.     You will see a brown residue that has been deposited along the top of the faucet or metal pan. Run your fingertip along the residue to pick it up.

Never is too late to make happy other persons, let’s make happy them with chemistry. I invite you to read more of magic chemistries in the references and see the videos below.

See you later chemist-wizards,

-Stephanie

References:
http://chemistry.about.com/od/demonstrationsexperiments/ss/burnmoney.htm
http://chemistry.about.com/od/chemistryhowtoguide/ht/smokingfingers.htm

What is Chemistry?

What is chemistry?

     In my previous entry I explain briefly that all have chemistry. Now the question is what is chemistry?

     Basically, Chemistry is the study of the matter, its properties and how and why substances combine or separate to form other substances. As I said before many people think of chemists as being white-coated scientists mixing strange liquids in a laboratory, but the truth is we are all chemists. Now, I am going to present a list of two things that I realize we all do without being conscious that we are changing physical or chemical properties of the matter.

  1.   From mix milk with coffee to sweeten the coffee we are doing chemistry. To mix milk with coffee we are mixing two liquids with different chemical and physical properties, they interact and produce a good taste to us.

How we know that this is change in the properties of liquids? Because if we taste only milk or only coffee we can realize that the tastes are different than when they are mixed. Also we can see that milk is white and the coffee is dark brown, so they have different colors which mean that they have different physical properties. Then when we mix it and we have prepared our coffee with milk, this is called a physical change of the matter.

Now, if we sweeten the coffee, we can see that the sugar dissolves into the mix. We again change the physical properties of the sugar because it passes from solid to liquid. Why  it is a physical change? Because if we changed the state of the matter of the sugar. We are not changing the chemical properties because we have the same sugar, if that would be a chemical change the sugar become to another thing. For example:

   2.  When we are into the woods. When we are into the wood and we turn on a wood fire we are doing a chemical change to the matter. Why? Because a log burning in a fire with the presence of heat and oxygen is transformed into carbon dioxide, water vapor, and ash. Now, we do not have the log because it becomes another thing: ash. And if we want our log again we have to find another one because we can’t reverse the ash to the log.

Usually, we can identify a physical change with key words as dissolves, state change, color change, odor change, and change in volume…etcetera. And a chemical change with words like: combustion, energy, oxidation, corrosion, etcetera.

     Summarizing, every day we practice chemistry doing physical and chemical changes to the matter. 

Now, I invite you to see the photos and the video below. If you want read more about chemistry click on the links in the references or copy and paste the link in search bar.

Thank you very much and have a nice week,

-Stephanie

References: video from: https://www.youtube.com/watch?v=gCbqjs-pqJo

http://www.livescience.com/45986-what-is-chemistry.html