Wednesday, 29 April 2015

Unit 4: Nano Particle Solubility and the Environment

 Okay, hold up, what the heck are nano particles?! How do they relate to solubility?? Well, nano particles are microscopic particles where at least one dimension is less than 100 nanometers (nanometers are one billionth of a meter) and they have a narrow size distribution. Basically, they're extremely small bits of stuff. Dr. Ananya Mandal from MIT defines them as "a small object that behaves as a whole unit in terms of its transport and properties." Nano particles are used in multiple different ways, primarily in the biomedical, optical and electronic fields - but also in some ways you'd never expect!

Applications of nanoparticles 

One cool way that nano particles are used is within your own clothing! Silver nano particles are often added to fabrics due to their ability to kill bacteria. They are also commonly found in cosmetics, soaps, personal care products, etc. When oxidized, the nano particles shed toxic silver ions, which knock off any bacteria. Theses charged ions of silver can interfere with important processes in living cells. As a result, key populations of bacteria and microorganisms could be severely damaged or mutated in soils and aquatic environments. This is concerning because when these ions reach the environment and dissolve, they could have harmful effects on the ecosystems upon which our food system depends. And as our global population grows, the release of silver ions into the environment is also expected to expand, via waste treatment and industrial processes.
Pathways by which man made particles are released into the environment. 

As well, bacteria aren't the only species at risk from the dissolution of silver ions. Larger creatures could directly or indirectly ingest them as well, for example, through the gills of a fish or the skin of a frog. We ingest them as well, through our food but also absorb them through our skin and breath them into our lungs. For larger animals however, the effects of silver ions has not been thoroughly studied and most likely varies based on mass, species and numerous other variables. As such, further research is needed to truly asses the dangers of silver ions on our environment.

Some ways nano particles can affect our bodies

Recently, scientists Peter Vikesland and Ronald Kent from the Virginia Polytechnic Institute have developed a new technique to study how nano materials dissolve in aqueous solutions. The goal is to help other scientists predict the effects of these nano particles on the environment and design safer materials. Other studies have examined the effects of groupings of nano particles, but not the singularly. Seems like it wouldn't matter, but think about it this way: a single snowflake melts a lot faster than a shovelful of snow. Their new technique focuses on how the particles dissolve alone to figure out how fast each individual one could shed ions. The biggest advantage to the procedure is that it allows the particles to be studied at similar concentrations found in the environment. Their conclusions will then be much more useful in the "real world".

The researchers fix silver nanoparticles at intervals along a glass surface, then expose them to different concentrations of sodium chlorides for two weeks. Then they examined changes to their size and shape. Their results suggest that chloride speeds up the shedding of silver ions from the particles, without forming sodium chloride. Dr. Bernd Nowack, a chemical engineer from the Swiss Federal Laboratory for Materials Science and Technology, says he can "envisage it eventually being used directly in the environment, in rivers or wastewater, for instance."

In my opinion, as dry as it sounds, this new technique seems to be pretty interesting! Especially with our growing global population and increasing pollution levels, understanding the effects of the materials we're using is very important. I find it pretty hard to believe that all these substances, not just including nano particles, are currently used without a comprehensive analysis of their long term environmental or health consequences. I also believe that more research is needed to fully understand nano particles and the effects of silver ions on the environment. Further studies are also needed to explore the effects on other basic forms of marine life; algae for example, or water fleas, as some experiments on them have shown that the individual coatings on different nano particles could be a 'driving factor of the toxicity'.

My questions to you: 

1. Why do you think silver nano particles would shed ions? What is this process called?

2. Can you think of any other applications of nano particle research? Why is this field so important?

3. Why does it matter if some bacteria get a little mutated or die off? We don't eat bacteria, right? So why should we care?

4. What would you tell someone who didn't believe in the risks of silver ions?

Monday, 27 April 2015

Unit 3 - Airbags: Friend or Foe?

Welcome back! In Unit 3 of chemistry course, we delved into the exciting world of stoichiometry, mole calculations, percent composition, percent yield, and all sorts of other new ways to calculate stuff. Today we're going to discuss a real world application of stoichometry (quantities in chemical reactions) and take a look at why this stuff matters outside a lab.

Airbags save thousands of lives each year in the States and here in Canada. But even after more than 2 decades after they've become mandatory in most cars, the auto industry still struggles to master the complex systems that must work flawlessly in less than a second. The recent recall of Takata air bags and General Motor's recall of their ignition switches highlights the problems that can occur when airbags actually deploy and when they don't.

A rundown of what actually occurs when airbags expand
Airbags are known for being extremely delicate and complex systems. The bag itself is made of thin nylon, which is folded into the steering wheel, dashboard, seat, or door. The sensor, typically located inside the dashboard, tells the device when to inflate. This happens only when the sensor detects collision force equal to running into a brick wall between 16 - 24km/hr. When this occurs, the airbag system ignites a solid propellant (similar to a rocket booster), which burns very quickly to produce huge volume of gas (ammonium nitrate). The gas then fills the nylon bag and literally bursts from its storage place into the vehicle at over 200mph.

Takata airbags, found in many new cars on the market today, have been recently recalled after new evidence came to light about the dangers they pose to drivers and passengers. Over 100 injuries and 5 deaths have been due to the airbags, who send metal shrapnel flying when deployed. Despite extensive research, a single cause has not been identified. Some suspect the ammonium nitrate itself, only recently used in their airbags, and hailed as a "new technological edge" by a company engineer (Paresh Khandhadia, 2009).

According to experts, ammonium nitrate breaks down over time and is very sensitive to temperature changes and moisture. Under these conditions, they say, it can combust violently (Hiroko Tabuchi, 2014). Interestingly, it becomes unstable at about 100 degrees. The inside of a car in summer may get as warm as 140 degrees! But it's cheap. Unbelievably so. Some say the switch from sodium azide (as seen in the inflation device diagram) to ammonium nitrate in 1998 was not for cost reasons, but for the environment. Ammonium nitrate produced gas much more efficiently with fewer emissions in their trials, says Alby Berman, a spokesperson for the brand. Either way, the company continues to use ammonium nitrate in their replacement air bags.

Another theorized issue is the quantity of ammonium nitrate involved in the equation. The New York Times published a video in 2014 depicting scenes of dropped air bag 'kits' and other mishaps on the assembly line. Sources who wished to remain anonymous told the newspaper that there was such enormous pressure to keep with demand, that sending potentially defective or damaged product back was not popular with management. If the amount of ammonium nitrate varied even a little from bag to bag, this could severely impact the resulting chemical reaction. As studied in stoichiometry, a change in the amount of reactants can completely alter the reaction itself. These unknown changes are not something you want coming at your face or your family's faces at 200 mph.

In my opinion, Takata is playing with fire. Using ammonium nitrate may be cheaper and 'produce less emissions', but at what cost? It seems almost crass to continue using the compound when it may or may not be involved in many deaths and injuries. Personally, I'm grateful neither of my parents cars use Takata airbags. Even though we've never been in an accident, it's still much better to know we won't have shrapnel coming at us inside our own car. I hope as much effort as possible is put into researching the cause of these malfunctions and correcting it. At the very least, ensuring quality product off the assembly line is a good first step.

My questions to you:
1. Do the benefits of ammonium nitrate outweigh the costs, in your opinion? After all, they don't ALL explode.
2. Should Takata have recalled only the airbags from cars registered in more humid/warm cities? Why or why not?
3. Compare sodium azide to ammonium nitrate. Why is sodium azide purportedly safer?
4. If you could give a piece of advice to the CEO of Takata, what would it be?

Sunday, 19 April 2015

Unit 2: Chemical Reactions within the Human Body

Unit Two of our Gr.11 chemistry course examines the different kinds of chemical reactions and how they may be used in variety of applications. Little do we notice, but these kinds of chemical reactions occur constantly within our very cells. These reactions keep us alive, maintain our pH, digest our food, and produce lots of energy.

Here we'll discuss step one in cellular respiration for eukaryotic (or more highly evolved) organisms, which is often the only step of cellular respiration in prokaryotic organisms. Cellular respiration is process of oxidizing molecules of glucose and trapping the energy produced in ATP. ATP, or adenine triphosphate, is basically the molecular currency of energy transfer. It's phosphorylated (sticking another phosphate on) from ADP (adenine diphosphate), storing energy in that chemical bond.

Before describing the series of chemical reactions that take place in glycolysis, step one of cellular respiration, let's talk about the two ways cells convert chemical potential energy from one form into a new one.

1. Substrate-level phosphorylation:
This happens directly in an enzyme catalyzed reaction, when ADP is phosphorylated into ATP, as explained above. During the process, about 31kJ/mol of potential energy is also transferred.

2. Oxidative phosphorylation:
This happens indirectly through a series of sequential redox reactions. It's a lot more complex than substrate-level and gives up plenty more ATP. The steps in the actual reaction are numerous and pretty complicated, so we won't get into them here.

An overview of the processes involved in cellular respiration and their location within the cell. 
Glycolysis is an ancient process that is believed to have evolved millions of years ago in single celled organisms, like yeast and some bacterium. It occurs in the cytoplasm of your cells. If you think about, its name tells you exactly what it does. Glyco - sugar, lysis - splitting/breaking. Basically, glycolysis takes a molecule of glucose, which has 6 carbons, and splits in half, producing two 3 carbon sugars, then later pyruvate and some ATP. This occurs in 10 enzyme-catalyzed steps. The first four steps essentially are composed of re-arrangement of molecules. Glucose is rearranged into fructose, etc. Steps 6 - 10 occur twice, once per 3 carbon sugar. The end result is pyruvate and some ATP.

After glycolysis, three other processes occur to round out cellular respiration. We won't get into them all here, as that's pretty much a whole unit of biology, but I encourage you to continue taking Bio and learn more about cellular processes. Photosynthesis is also covered, which is super cool as well. If you think you might be interested in this kind of material, but in greater depth, you should definitely think about continuing in biology or biochem. 

This information is mainly biology based, but it is pretty cool to see how the two sciences intersect. We've got a lot of organic chemistry going on here too! I find it can be hard to think on such a tiny level - within a cell, within an organelle, within a particular part of an organelle! Crazy. I also think that it is important to understand what processes occur in your body, where and why. Learning more about the body's complexity makes me even more in awe of how amazing they are and gives me an even deeper respect for them. 

My questions to you: 

1. Identify the type of chemical reaction that occurs in step 4 of glycolysis. How do you know? 
2. What do you think the next step of cellular respiration would be? Why? 
3. Why do we need to 'spend' ATP to get glycolysis going? Is there a way around that? 
4. Explain why catalysts are important throughout glycolysis. What's their purpose?