Chemistry of Everyday Things

Background and Rationale

I teach in an Urban High School that has a demographic population of 98% African-American, 1% Hispanic, and 1% Caucasian students. My typical student is a 10 ^th to 12 ^th grader, enrolled in Algebra II, and has difficulty transferring Science and Math solutions to real world problems. Most of my students dread Math, and view Science as irrelevant to their lives. I intend to change this paradigm for my students by allowing them to master useful science skills that they can visualize to have a positive impact on their lives for years to come.

As a fourth year teacher, I realize that what motivates my students is my passion for a topic combined with them discovering, through inquiry based learning, aspects of the world around them that had gone unnoticed before. Supporting them in becoming masters of their own environment transforms their perspective on life, and overcomes barriers of racial issues, low self-esteem issues, and not understanding how to cope with their world. I want to have students experience everyday Chemistry in such a way that they can visualize the way the world works. Since Energy and Clean Water will be 'hot topics' for the next hundred years, I look forward to seeing my students become active participants in our global society.

Constructivist theory, scaffolding, and spiraling are three pedagogical approaches that will be intertwined throughout the unit. The constructivist theory is that "children learn best when given the opportunity to construct knowledge from their own experiences" (3). Thus, having students conduct 30 experiments that the students merely follow a set of directions will not have as much value as having my students conduct the same 3 experiments ten times, each time analyzing and thinking about a different facet of the experiment and each time gathering new lab skills. This latter aspect is referred to as spiraling, the pedagogical approach that has students revisiting a topic, but looking at it from a different viewpoint. Scaffolding is a pedagogical approach that uses consecutive skill sets to teach something. The skill sets are taught in an order such that skill 3 needs skill 2, and skill 2 needs skill 1. Thus, if you wanted to teach someone how to balance their checkbook, you would first teach them how to identify and count money, then how to add and subtract money, and finally how to balance their checkbook. In combining these three pedagogical approaches with three complex experiments and topics that could very well impact our nation's future, I hope that students will become comfortable taking risks, analyzing their manipulations of a topic, and adjusting their process moving forward (4).

Biodiesel – The Science and The Process

Biodiesel is a diesel fuel that can be used in any unmodified diesel engine. It is an excellent lubricant, and an excellent organic solvent. Although biodiesel is nontoxic and biodegradable, it can cause degradation in certain types of hose and gasket materials (5). Biodiesel is extremely efficient, and can also reduce global warming and tailpipe emissions, although it may increase nitrogen oxide emissions (6). Biodiesel is usually combined in the commercial market with regular diesel as a substitute lubricant for sulfur. In fact, the U.S. Government has recently mandated that by 2012, all of the diesel fuel sold at gas stations be combined with biodiesel instead of sulfur (7).

Biodiesel is considered a renewable resource because it can be produced from plants and waste vegetable oil, and can be put directly into any unmodified diesel engine. Feedstock is the material that is gathered to produce biodiesel, the most common of which is waste vegetable oil (WVO). The feedstock used is an important consideration when determining the viability of biodiesel since obviously, by producing more crops for biodiesel, we are competing for the same resources used to produce food, inherently increasing the cost of our own food supply. Studies have shown that if we planted every available acre in the United States, we could not actually produce enough biodiesel to meet our demand for supply (8). However, if biodiesel is produced from WVO gathered locally (from restaurants, schools, and hospitals) and produced in small quantities, referred to as microproduction, then biodiesel can become a very viable option that adds to the sustainability of a community (9).

Whatever the feedstock used, it is combined with an alcohol and a catalyst to produce biodiesel fuel (a methyl ester compound). This process is called transesterification. During transesterification, when the fatty acids in the vegetable oil are separated, glycerol is produced as the byproduct (See Appendix A, Biodiesel Production Process). Glycerol can be further utilized to make many products including detergents, soaps, lotions, and fertilizers (10). The table below explains the process using a skeleton reaction:

The conceptual process for producing biodiesel from WVO in a classroom environment is simple. Essentially, WVO is collected, allowed to settle, and filtered. For larger quantities, a sample of the WVO is then combined with a solvent mixture (50% isopropyl alcohol, 50% toluene) and titrated with a 0.1% sodium hydroxide solution. The amount of solution needed to complete the titration determines the amount of potassium hydroxide that needs to be added as a catalyst. For beginning Chemistry classes creating microscale amounts of biodiesel, a simple chart can determine the amount of catalyst needed.

The WVO is heated, and the methanol is added (in a 5:1 ratio) along with the catalyst (usually potassium hydroxide or sodium hydroxide). The mixture is stirred and then allowed to settle for the next step. After the mixture is settled, there will be two insoluble layers (biodiesel and glycerol) which need to be separated; since the glycerol is heavier, it will settle and separate below the biodiesel. The glycerol can be drained so that the biodiesel (top layer) is ready to 'wash'. Washing is a term used to describe the final portion of the process that removes any remaining contaminants in the biodiesel. The most common method of washing the biodiesel is called water washing, where water is mixed with the biodiesel and allowed to separate. When this portion is complete, the water (now the bottom layer) is drained, and the biodiesel's pH is tested to ensure that it falls within the tolerable range (5). The washing process is repeated until the desired pH is attained (See Appendix A), at which time the biodiesel is ready for use.

Water Purification, Filtration, and Distillation – The Science and The Process

The topic of clean water (or lack thereof) is a well researched issue that is critical for our survival. Although the social issues caused by lack of clean drinking water are beyond the scope of this unit, the overarching problem must be addressed with students who are most likely unaware that a problem even exists. As one panel with the National Science Foundation put it,

"One of the most pervasive problems afflicting people throughout the world is inadequate access to clean water and sanitation… 1.2 billion people lack access to safe drinking water, 2.6 billion have little or no sanitation, millions of people die annually – 3,900 children a day – from diseases transmitted through unsafe water… Problems with water are expected to grow worse in the coming decades, with water scarcity occurring globally, even in regions currently considered water rich. Addressing these problems calls out for a tremendous amount of research to be conducted to identify robust new methods of purifying water at lower cost and with less energy, while at the same time minimizing the… impact on the environment." (11)

Even with this urgency, most students are not aware of the differences of water purification, filtration, and distillation. If put in the context of a natural disaster, most citizens are helpless to acquire the basic necessity of life – clean drinking water.

Clean drinking water is usually understood to mean water that is free of pathogens, particulates, waterborne bacteria, enteric viruses, and is generally clear and transparent (4). However, just because water is clear (free from particulates) does not mean that it is safe. Water purification is generally accepted as the multi-step process to remove contaminants from surface or groundwater so that humans can consume it without getting sick. Water filtration is usually understood to mean the process that separates the solids (particulates) from the water. Water distillation is the process of purification of water through vaporization, condensation, and collection of pure water distillate. In a natural disaster, all three processes should be used in conjunction to ensure that water is drinkable (11).

Water purification processes have evolved as technology has progressed. India used the Ultra-Violet (UV) rays from the sun 2000 years ago to purify the water, while today we use UV Lamps to simulate the same effect (12). UV light has been proven effective in the removal of many bacterial pathogens. The germs proven effective to kill with UV light include: bacteria - Escherichia coli, vibrio cholera, salmonella, shigella flexneri, campylobacter jejuni, yersinia enterocolitica, virus – rotavirus, and parasites – giardia, and cryptosporidium (13). Even though UV light can kill these germs, it is important to note that UV light is ineffective at killing viral pathogens. There is, however, currently promising research in using photons combined with engineered nanostructures to catalyze materials that inactivate viruses (13). In analyzing the processes of the past while looking to the processes of the future, better decisions can be made as to water systems that are viable to implement.

Currently, a patented water purifying unit (14) developed by Rolf Engelhard offers a viable purification system that takes weaknesses of other systems into account. This unit will have students recreating the model using everyday parts, and testing the model before placing it in the distillation unit. Essentially, there is a cylindrical column in which water that needs to be cleaned passes through. As the water enters the cylinder, the water is exposed to UV light as the water is forced into a swirling pattern. This allows for germs to be killed before entering the filtering portion of the column. The water then goes through an activated charcoal filtration system that is mounted 'about' the UV light. (14) The inventor noted in his patent that other systems release the water after the charcoal filter, assuming that the water is clean. However, if there are accumulated particulates which themselves had grown bacteria on the exit portion of the activated charcoal, then the system would be rendered useless. Thus, to prevent accumulated germs from recontaminating the water, the water is exposed (for the second time) to a UV light before exiting the purification filter to be prepped for the distillation unit. Once the water is in the distillation system, it can be distilled until the end result is clean, purified, filtered, distilled water.

Bioethanol – The Science and The Process

Ethanol is an alcohol that consists of two single bonded carbon atoms that have a hydroxyl group at the end of the chain. Bioethanol simply refers to ethanol that was produced from a renewable feedstock, and thus for the purposes of this unit, the terms will be used interchangeably. Ethanol is produced when the feedstock is fermented with yeast in an oxygen deprived environment. The fermentation process converts the sugars (usually glucose) from the feedstock into ethanol. The byproduct of this fermentation process is carbon dioxide (15). Thus, the formula looks like this:

Bioethanol is a biodegradable, clear, colorless, extremely flammable liquid that can be produced from corn, sugar cane, and even grapes (16). Due to cost, bioethanol in the U.S. is most commonly produced from corn, while Brazil uses mostly sugar cane. Unfortunately, the entire corn plant cannot be easily fermented, and thus only the corn kernels are used to produce bioethanol. Cellulosic bioethanol is ethanol produced from plant stocks, trees, grass, and other biomass. As opposed to sugar cane and corn whose sugars ferment into glucose, cellulosic biomasses need to have their cell wall components broken down so that the cellulose is exposed. Only then can the enzymes break the cellulose further down into glucose or some other form of sugar so that they can ferment into cellulosic ethanol. Also, cellulosic ethanol needs to be distilled since other biofuels can sometimes form as byproducts (17). Even with all of these drawbacks, however, cellulosic bioethanol deserves further study, since using corn is competing with the nation's food supply. In fact, as with biodiesel, if every available acre of land in the United States planted corn, we could not produce enough ethanol to meet our demand for supply (6). Further, cellulosic feedstock is much more available and can be grown using less water and pesticides than is necessary for growing corn. Waste product cellulosic feedstock that can also be used to produce ethanol include grasses, forest excess growth, city waste, and even some forms of fast growing trees (18).

Bioethanol is already in gas stations across the country, since gasoline now commonly includes ethanol in the mix. Although this works well to increase the octane rating and efficiency in unmodified gasoline engines, ethanol does not have the same energy output as gasoline (10). Although bioethanol produces CO ₂ as a byproduct, the net effect is negligible since the CO ₂ that ethanol forms when burned was absorbed by the plant as it was maturing. Thus, it is said that ethanol is CO ₂ neutral (18).

The process of making bioethanol is complex for larger quantities, but relatively simple for a classroom laboratory. In a sterilized container that can be covered with a flexible top, place water, corn meal, sugar, and yeast into it, and then cover. The cover should be flexible like a balloon or finger portion of a latex glove (allowing one glove to cover 5 containers). Allow the mixture to sit in a warm location for several days, or until the flexible cover stops reacting. If the top comes off, you must start over, as the feedstock needs to ferment in an oxygen deprived container. Decant the solution above the precipitate matter into a container suitable for distillation. Distill the liquid using a condensation column, making sure that you have a thermometer in the boiling flask, being careful to not use open flames as the solution is very flammable. The distillate that condenses at a boiling temperature of 78 C (173 F) is ethanol ready for use as fuel (19).