Monday, January 7, 2013

The Envelope Please

In the fall term I challenged my students to write an essay about the fundamental concepts of matter.  We did a series of activities in class to learn about the classification of matter such as a POGIL (inquiry based learning activity), separating a mixture, and the classic iron and sulfur lab.  Through these activities and labs, the students built an understanding of elements, compounds, mixtures, physical and chemical properties, and physical and chemical change.  In the past I would end this unit with a test on these concepts, but this year I decided to try the essay challenge as the final assessment.  Using their experiences, they were charged to write a thoughtful and interesting essay about matter.

As an extra incentive, I promised to post the best essay of the class on my blog.  I thought that one essay would stand out as the clear winner, but I was very wrong.  I had several very good essays that exceeded my expectations.  The choice of one winner put me in a complete deadlock.  I just couldn't choose my favorite ONE essay.  So I sat on it for way too long, just stewing and putting off my students inquiries.  Well, tonight I'm going to announce the winners of the essay contest.  In the spirit of the fall term sport assembly, I have chosen two students to be the winners of the matter essay challenge.

And the winners are...

Bailey Mae Bone and Quinn Taylor

Congratulations on your excellent writing.  Both essays are posted on the blog.  Enjoy.

Quinn Taylor

Bailey Bone

Why Does Chemistry “Matter”? by Quinn Taylor

Why Does Chemistry “Matter”?
            Matter. It is what makes up the entire universe, and makes us what we are today. From magnificent glowing stars millions of light years away, to the tiny, dim night light in a child’s room, it consists of matter. This concept of understanding the make-up of everything we know and will know is not a straight forward thing either. It can take on many different shapes and forms, such as compounds, elements, mixtures and much more. Matter can even go through numerous and exciting changes, making it an intriguing topic to study upon. As scientists have been discovering for thousands of years, science is an incredible thing, and can be very fascinating once you delve into its secrets.
            The most basic building block of matter is of course the element. An element is the smallest thing that a substance can be broken down into without splitting atoms. A great example of a common element is the gas Oxygen (O). Another example of elements would be the breaking apart of the compound Sodium Chloride (NaCl), or table salt, as we casually call it. When salt is broken down into its smallest parts, you will have the elements sodium and chlorine left over. These combinations of two or more elements are called a compound. In a compound, the elements are chemically bonded together through a chemical reaction to form something new. As learned in the POGIL activity, the majority of our items that we use and see on a daily basis are compounds. A few examples of these items are water (H2O), Chalk (CaCo3), carbon dioxide (Co2), acetaminophen (C8H9No2), and much more. You would be surprised to know that these reactions are occurring everywhere all the time, even without us knowing it. Not all of these reactions are big, or drastically change the substances interacted with it, but life would be impossible to sustain without them.
            These common changes can come in many ways, shapes, and forms, including physical and chemical changes. A physical change is a change to the substance that does not affect what substance is or its chemical makeup. These changes, such as tearing, cutting, dissolving, freezing, evaporating, condensing, affect the substance without changing it molecular makeup, therefore classifying it as a physical change. Chemical changes, on the other hand, do change the substance and its molecular makeup. Examples of these types of changes can be rotting, rusting, digesting, eroding, burning and reacting with an acid. If a chemical change occurs, you cannot get back the original substances without using some form of a chemical or having a chemical reaction occur. It is easy to know when a chemical reaction is occurring to your substance though. Common side effects from a reaction may be smoking, heat expulsion, smell dispersion, bubbles (creation of a gas), formation of a precipitate, and a change in color. As we saw in the iron and sulfur lab, many of these things will occur at the same time. When our reaction occurred, we observed heat expulsion, smoking, and a change in color, and of course, the nasty smell that this experiment is famous for. During this reaction though, not all of the material was used or fused, leaving a mixture left over in the test tube.
            A mixture is a combination of two or more substances either dry (such as sand) or in a liquid (such as sugar water). Compared to a pure substance, mixtures are fairly easy to spot. A pure substance is a material that has the same concentration of molecules throughout its entirety, while also only consisting of one type of molecule. Examples of a pure substance might be salt, sugar, and the other items listed previously, as all elements and compounds are pure substances. If you were to look at a mixture at a molecular level compared to a pure substance, it would look drastically different. The mixture would have many different molecules, particles and substances within it, while the pure substance would only have one. Even with the naked eye, these differences are as obvious. A pure substance is usually uniform, while a mixture contains clumps, bubbles, different colors, grain sizes, and textures. Even more surprising is that it is actually easier to separate one of these crazy mixtures than to separate a plain compound, as a chemical reaction is needed for the compound’s separation. As we learned in the Separation of a Mixture Lab, this makes sense as a mixture can be separated fairly easily. Ways to separate a mixture could be boiling, evaporating, sifting, magnetism, filtering, and much more. When you actually dig down to the bottom of these many different forms of matter, it is actually easy and fun to tell them apart and to separate them in the lab!
            Chemistry is one of the biggest and fastest growing branches of science out there right now. From searching for cures for diseases such as cancer, HIV, and even the common cold, to just trying to be the discoverer of a new substance, chemistry has brought, and is still bringing joy and learning to millions of people around the globe. As we have learned through our many experiments over the past weeks, matter is the basic building block of everything. Once you get past the nitty gritty, and nuts and bolts of these basic principles (and even these aren’t too difficult), many will discover that this field is fascinating, and has the potential to benefit and affect us as students, and possibly even our society, in the rest of lives soon to come. 

Classification of matter essay by Bailey Mae Bone

Classification of matter essay

            “Science ... is organized common sense.” Josepsech Alexander Leighton. Just like Leighton said, science is common sense; so too is the classification of matter. The smallest building block of the classification of matter is, simply, matter. Matter is any substance or material comprised of molecules and atoms. The classification of matter places matter into different categories including elements, compounds, substances, and mixtures, based on its physical and chemical properties.
            The simplest classification of matter is an element. An element is a substance that is composed of one single type of atom that cannot be broken down. Elements are organized on the periodic table and are characterized specifically by their unique atomic number. People come across elements everyday, from the Gold and Silver in our jewelry to the Nitrogen and Oxygen we breathe. There are 118 known elements on the periodic table today, starting with Hydrogen and ending with Ununoctium.  A more complex category in the classification of matter is compounds. A compound is a substance that consists of more than one type of atom chemically bonded together. In a compound every molecule is the same and can only be separated chemically. Compounds are made up of elements. For example, table salt is Sodium and Chloride and water is Hydrogen and Oxygen. What distinguishes compounds from elements is that elements cannot be separated but compounds can. Because of the unlimited combinations of elements, compounds cannot be classified on a simple table like elements. When doing the classification of matter POGIL, I learned that both compounds and elements are pure substances because their composite particles are identical. In the ‘separating-a-mixture’ lab, I worked with my group to separate Iron, salt and sand. This experiment allowed us to appreciate that Iron is a single element while salt is a compound and sand is a mixture.
            Just as an element is a simple category in the classification of matter and a compound is more complex, a pure substance is simpler than a mixture.  A pure substance is a form of matter with uniform molecules. Elements and compounds are pure substances but elements are in their simplest state and compounds can be chemically broken down into their separate components. In contrast, a mixture is formed when more than one type of matter is mixed together. Mixtures can be composed of pure substances and can be separated chemically or physically. Mixtures are described as either heterogeneous or homogeneous. A homogeneous mixture looks the same throughout whereas a heterogeneous has visible differences. For instance, chocolate ice cream is a homogeneous mixture whereas chocolate chip ice cream is a heterogeneous mixture. In class we observed the distillation of cherry coke. This demonstration showed us how the heterogenous mixture of cherry coke was separated into water, carbon dioxide, and flavoring. We also learned about the method of chromatography which separates mixtures using water and chromatographic paper.
            Simple and Complex categories of matter are described using physical and chemical properties. Physical properties can be classified either qualitatively or quantitatively while chemical properties describe how substances react with other atoms or molecules to produce new substances with different properties. Qualitative physical properties are those that can be visually observed about a substance. Shape, texture, color, and state are examples of physical properties. Unlike qualitative physical properties, quantitative physical properties deal with numbers and are labeled as intensive or extensive. An intensive property such as density or boiling point is the same regardless of quantity. In contrast, an extensive property such as volume or mass does change with quantity. As opposed to the physical properties of matter, the chemical properties of matter detail reactions with other particles that produce new substances with different properties. Reactivity to acid, pH, and heat of combustion are chemical properties. Physical and chemical changes are used to accurately observe properties of a substance in a lab. A physical change as it relates to matter does not change the structure of atoms or molecules; it only affects physical properties. Melting, freezing, condensing, and dissolving in water are all physical changes. A reaction to a substance that produces a new substance with unique chemical properties is a chemical change. Burning, oxidizing, or reacting with acid are all chemical changes. Chemical changes may or may not be reversible. One way to tell if there has been a chemical change is to look for a the formation of a precipitate, a color change, a change in temperature, or a production of a gas. During the Evidence of Chemical Change Lab and The Iron and Sulfur Lab our class observed drastic chemical changes that alter both the appearance and properties of a substance.
            In conclusion, science categorizes matter many different ways; into substances, elements, compounds, and mixtures while describing it as having chemical or physical properties, but from the copper pennies in your wallet to the gold ring on your finger, ‘matter’ will always ‘matter.’