Archive for the ‘MSTQE’ Category

Science Makes Sense Week 3: Organic Chemistry-Nomenclature,hydrocarbons, alkanes, whales and petroleum

September 7, 2015

Man has always been in need of energy sources; starting with the discovery of fire. From the middle of the 17th century till the late 19th century , whale hunting was prevalent to such an extent, that certain kinds of whales, like the blue whale, the sperm whale ,were hunted for their oil till they almost became extinct. Whale oil was a necessary source of fuel and heat including whale oil for lighting, as well as for candle waxes and even in the processing of textiles and soap. An unexpected gush of oil discovery in Pennsylvania, USA,  is considered the beginnings of the use of fossil fuels for Western energy sources in the 19th century. In China and Iran, seep oil as it was called,  was used for fuel from early times. (4th century through 16th century)

What are fossil fuels and why do we call them that? Basically it is animal remains under great pressure and temperature over years and years that converts to crude petroleum. The distillation of petroleum leads to myriad products that literally fuels our every day life.(Distillation is a chemical process that starts with heating crude petroleum obtained from oil rigs and separated into several solids, liquids and gases used for fuel and other purposes.)

Every third week we will study organic chemistry. If you look at  the Periodic Table, you find that the 6th element is carbon. Carbon is such a busy element because it can combine with other elements to form hundreds of carbon compounds. The study of these compounds has been named Organic Chemistry to distinguish it from Inorganic Chemistry, which is the study of the rest of the elements in the Periodic Table!

Today we will look at one of the combinations of carbon and hydrogen or compounds comprising hydrogen and carbon; these are called hydrocarbons. ( A compound is a chemical combination of two or more elements.) The first series of hydrocarbons have the general formula shown below and are called alkanes or paraffins.

CnH2n+2

The first alkane in the series has n=1 which makes 1 carbon atom combine with 2×1+2=4 hydrogen atoms to give :

C1Hor CH4

as we commonly write it (when there is only one atom of any element you do not need the subscript 1 for it)

This hydrocarbon compound is named methane. Methane is also called ‘marsh gas’.  As the second name suggests,  it  is a gas and is also highly flammable. Methane is the main component of natural gas used at homes and other places for cooking purposes:IMG_2239IMG_2237

Now let us make n= 2 and  we get the second compound in the series called ethane;  (n=2, so there are 2 carbon atoms and 2×2+2=6 hydrogen atoms) and the formula is   C2H6 for ethane.

The next compound in the series (n=3) will be three carbon atoms combined with 2×3+2 =8 hydrogen atoms called propane

written like this/ chemical formula : C3H8

When n=4, we have 4 carbon atoms combined with 2×4+2=10 hydrogen atoms called butane and written like this/ chemical formula: C4H10         

So far we have seen methane, ethane, propane and butane; all four are gases at room temperature. Notice all end in ‘ane’ and are all called alkanes.

When n=5 we have 5 carbon atoms combined with 2×5+2=12 hydrogen atoms and the name is pentane. From now on the names will be the latin word for the number so 6 carbon atoms will be called hexane and 7, heptane. 8, octane, and so on. As you notice the formula for pentane will be  C5H12 , for hexane : C6H14, for heptane; C7H16 , and for octane: C8H18.

The first four alkanes were named before the nomenclature (a fancy word that means ‘naming process’)was decided.

Ethane is also used along with methane as natural gas for cooking purposes. Propane is used in propane tanks for outdoor grills. Butane is the fuel used in cigarette lighters and butane torches. Pentane is a low-boiling liquid used as a solvent and in the creation of plastic foams, hexane( liquid) is used in gasoline, and in industry as a solvent. Heptane has 0 octane rating and is not used as a fuel for gasoline since it causes high engine knock., it is used as a solvent in industry. Octane has good octane rating ( obviously) and is a major component of gasoline.

We have looked at the formula and uses of at least 8 alkanes, but it is important to picture how the arrangements of atoms or structure of these compounds looks like. Using simple materials like toothpicks and marshmallows or raisins one can construct these compounds. Here is a picture of the first three alkane compounds: methane, ethane and propane. As you can see, they are three-dimensional structures; for methane, one can see the tetrahedral structure of the compound.(The carbon atom is depicted by a tomato, and the hydrogen atom is depicted as a marshmallow here. The toothpicks are supposed to indicate the bond between the atoms; distances between the atoms, sizes of the atoms here are not accurate, but these models help understand structure.)

IMG_2243

Next time (Week 6) we might be able to look at structure a little more closely and learn more about structural differences.Most of the alkanes studied today are the by-products in the distillation of crude petroleum. As you can see they are invaluable in our everyday life. However, next week as we look at Chemistry and Social Justice, we will talk about the problems in our society as a result of our over-dependence on petroleum/ fossil fuels.Careening from the near extinction of whales we are now at the point of near exhaustion of our fossil fuel energy resources.

Activities for middle school teachers: Let students figure out the structures of nonane, (9 carbon), decane etc till , say n=20. Students can also draw a graph using graph paper, making the number of carbon atoms on the x-axis, and the number of hydrogen atoms on the y-axis and plot a graph.(For example the x point for methane will be 1 unit and the y point will be 4 units.) What will be the shape of the plotted points? Why? Can the student now predict the structure of any alkane from that plotted graph? How will they do it?

If the language arts teacher is reading “Moby Dick” by Herman Melville, students will have an idea about the hunting of whales for whale oil two centuries back.

Nuggets of Information:The word ‘petroleum’ comes from 2 Greek words,’petra’ for rock and ‘oleum’ for oil.

Only the Inuit people have the legal rights to hunt whales today.

In 1859,workers in USA discovered petroleum jelly as a by-product in the oil rigs . They were not too happy with the sticky product, but found it was effective in the treatment of minor scratches and bruises. Today it is sold as Vaseline.

References:

http://www.scienceclarified.com/everyday/Real-Life-Chemistry-Vol-3-Physics-Vol-1/Organic-Chemistry-Real-life-applications.html

http://sjvgeology.org/history/index.html

http://io9.com/5930414/1846-the-year-we-hit-peak-sperm-whale-oil

http://www.petroleum.co.uk/alkane-chemistry

http://historicaltidbits.blogspot.com/2012/05/petroleum-jelly.html

http://www.newworldencyclopedia.org/entry/Petroleum

Science makes sense Week1: On Inductive, deductive reasoning, Ernie and Bert and other things

August 24, 2015

A big hello and welcome to all my science, math students, especially to the MSTQE group! Anybody who is intrigued by/ enjoys / wants to know more about science are also welcome here. Please comment and share your ideas. I am just a facilitator who wants passion and energy to flow here. I will make connections with different branches of science, include social justice issues, activities for teachers and nuggets of information. I hope teachers of science in middle school gain confidence and love for science to impart it to their students.

I am reading a very informative book called ” The Story of Science” by Susan Wise Bauer, which she says she is writing for people who are not into science. Personally I think all of us in the scientific field can enjoy her historical travels. She traces the history of science (when she says science she definitely includes math which I consider to be the queen of sciences) from several centuries BC to the present century. I will focus on her discussion of deductive and inductive methodology.

From the time of Aristotle ( 300 BC) deductive reasoning was well known.Deductive reasoning starts from general statements to specific conclusions. You start with a premise and come to a conclusion.   No experimentation was done to get to the conclusions.  The Aristotelean method survived for centuries. (This is similar to the hypothesis that students start with in a science fair experiment.) Many centuries later,( almost nineteen centuries later)  during the time of Queen Elizabeth I (1612), Francis Bacon who had served in her court started thinking a little differently. He felt that deductive reasoning could distort evidence. You could play around with the evidence to suit your hypothesis. He was of the opinion that inductive reasoning would lead to more useful information. You start from specifics, work on experimentation and then come to a general conclusion. So you may have a hypothesis at the beginning ( not at the end like Aristotle) do some experiments and then come to a conclusion. This is what we call a scientific method.  The concept of experimentation  to prove something started in the Western world with Francis Bacon.

This was continued by William Harvey who, through dissection of the human and animal bodies proved how blood circulated in the body. Again, Copernicus proved through his mathematical observations that the sun, not the earth was the center of our universe. Deductive reasoning was being replaced slowly by inductive reasoning.Remember, all these pioneers had to fight against popularly held ideas that followed deductive reasoning and were ridiculed  for their innovations.

Think about the invention of the wheel by early man( or woman?). Perhaps a piece of stone with corners was used first. Perhaps with more and more corners, the movement of the stone along a pathway improved and with time people realized that a structure with no corners or infinite corners , in other words a circular object, works best as a wheel. ( There used to be a remarkable episode with Ernie of Sesame Street philosophizing about the shape of a circle. Ernie says to Bert, ”  You think a circle has no corners or maybe, just maybe it has infinite corners?!”) Another amazing early case of inductive reasoning.

Following Francis Bacon’s inductive reasoning, we have Robert Boyle in England,  a little later in the seventeenth century, who started working with elaborate pieces of equipment to find relationships between pressure and volume of gases . So the place where he did his experiments was called elaboratories. The word laboratory, or short form ‘lab’ is derived from this word just  four centuries ago.

It is important to note that deductive reasoning is still applied in philosophy, social sciences and even sometimes in science,especially in mathematics, but inductive reasoning is a valuable additional tool for scientists.

Activity for middle school teachers: Check what the language arts teacher/ social studies teacher is covering in his/her class. If the subject is Shakespeare, or anything to do with Queen Elizabeth the first, then bring in seventeenth century Francis Bacon etc to compare inductive and deductive reasoning.

Nuggets of information: On August 17,1835, the tool we use a lot, a wrench, was patented.

The Chemist Hazel Gladys Bishop was born on August 17, 1906. She designed the first long lasting lipstick!

lab in 17th centurylab1

Here is a picture of a laboratory or elaboratory from the seventeenth century; the picture next to it is from the Chemistry Department of Northeastern Illinois University, showing present day laboratory equipment.

References:

Bauer, Susan Wise, The Story of Science, ( W. W. Norton and Company 2015)

https://duckduckgo.com/?q=images+of+laboratories+from+the+seventeenth+century&ia=images

http://www.science20.com/the_science_of_motherhood/this_day_in_science_history_august_17th