THE CHEMICAL WORLD MEASUREMENT PROBLEM SOLVING AND MATTER ENERGY chemistry assignment help

 

 

Part 1: The Science of Chemistry, Measurement, Problem Solving, and Matter

 

So, What is Chemistry, and Why Does It “Matter”?

  “The most incomprehensible thing about the universe is that it is comprehensible.”

  —Albert Einstein (1879-1955)

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So, what is chemistry? What do chemists do? Science is a way of merely looking at and trying to understand the natural world that surrounds us. Have you ever wondered why you need oxygen to survive? Why, when you throw a match into a puddle of gasoline, does it burst into flames? Why, when you mixed together baking soda and vinegar in elementary school to make a volcano, it “erupted”? One particular branch of science, chemistry, seeks to answer questions related to all of these examples, and more. Chemistry is the study of matter [anything that has mass and takes up space, thus it is pretty much everything that “is”]—what it is, and how it interacts with itself to produce all the things that exist in our universe.

Chemists, then, are scientists who study matter, the basic building blocks of which are atoms and molecules. Atoms and molecules behave a certain and predictable way, and they possess certain properties that govern this behavior, and that’s what you will be studying. So, in chemistry, you focus on these atoms and molecules in an effort to understand the properties of the matter that they compose.

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The Scientific Method

The way that chemists, as well as all scientists, approach such study and investigate our natural world is via an approach known as the scientific method. In its simplest form, this method begins with some sort of observation that leads to a question. For example, you notice that a tree limb burns when placed on a fire, but a metal coin does not. Why? You then formulate a hypothesis (a tentative explanation) about what you’ve observed or a problem you’ve noticed. For example, do only items made of wood burn, and not items made of metal? A hypothesis might then be that anything made of wood will burn on a fire, while anything made of metal will not. Then, you may devise a test or experiment for this question or hypothesis. You may take several samples of different types of wood and several samples of metal items and place them on a fire to see if they burn. You would then record and analyze your data, and draw conclusions or formulate a model that explains the results you obtained, and ultimately, answer your starting question.

If you or others make a lot of similarly related observations, you may be able to summarize them all in the form a scientific law. If one or more similar hypotheses stand the test of time and become firmly accepted amongst scientists, they may lead to the development of a scientific theory. Hypotheses, laws, and theories result in the ability to make testable predictions—testable via experimentation. Such tests require very controlled procedures that ultimately yield new and important observations. If such predictions are not verifiable, or if they cannot be confirmed, the model (theory), hypothesis, or law must be modified accordingly. It is thus a dynamic, self-updating way of understanding the universe.

Definitions:

Law. A scientific law is a generalization or statement that describes some aspect of the universe, and that seems to always apply under the same conditions in a causal relationship.

Theory. A scientific theory is a model that describes or explains the reasons behind certain observations and laws. A scientific theory is not to be taken lightly—it is not just a “guess” or an idea as would be implied by the use of the term in the general public. In science, a theory carries a lot of evidence-based weight, and offers a very strong explanation for the phenomena it explains.

Units of Measurement

When measuring all of these observations related to matter, scientists use the International System of Units (SI), which is based on the metric system (i.e. meters, kilograms, centimeters, etc.). Actually, the U.S. is the only developed country in the world that does not use the metric system in everyday life; though our scientists use SI units, our citizens still use the English system of measurement (inches, yards, pounds, etc.). But you must use the SI system to solve chemical problems and perform dimensional analysis. Dimensional analysis involves using equivalencies to perform such operations as conversions, predictions, etc. The base units for the SI system include the meter (m) for length, Kelvin (K) for temperature, second (s) for time, and kilogram (kg) for mass. We can combine these units with other units to derive other commonly used units of measurement of which you may have heard: cubic centimeters (cc or cm³) or cubic meters (m³) to measure volume, grams along with cubic centimeters to measure mass and density (g/cm³), and many others. But when we actually measure amounts with laboratory instrumentation, we can never achieve a perfect value because of the inherent limitations of the tools with which we are working. So, when we report our measured values, we do so in way that reflects our measurement uncertainty. We adjust the number of digits accordingly, and any digits that we use when reporting our measurements that are not simply holding place are termed “significant” figures.

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Types of Matter

The matter that we study in chemistry can exists in different states, i.e. solid, liquid, and gas. The difference here has mostly to do with the space between molecules and the amount of energy they possess in each case. It can also exist in different compositions, i.e. pure substances and mixtures. If it is a pure substance, it can be an element, which is a form of matter that cannot be broken down any further into simpler forms of matter. In other words, it’s the simplest form of matter possible. A compound, on the other hand, is matter that is composed of two or more elements, but in fixed proportions. For example, a block of solid aluminum (Al) is elemental matter. However, a block of table salt (NaCl—sodium chloride) is a compound, because it is made of at least two different elements (sodium and chlorine), and the proportion is always a 1:1 ratio (1 sodium atom present for every 1 chlorine atom present). But it is still a pure substance so long as no other elements are present in any other combinations or proportions. A mixture, however can be separated further into its components—it is not in its simplest form. It can be a homogenous mixture, in which it has the same composition throughout (i.e. salt water), or it can be a heterogenous mixture, in which different regions of the sample will have different composition of its components (i.e. rocky road ice cream—some bites will have  more marshmallow than others). This can be summarized in this flowchart.

Properties of Matter and Energy

The properties that matter possesses (that explain the way different samples of matter behave) can be either chemical or physical in nature. For example, gasoline is flammable. That is a chemical property, since it is a reaction with oxygen that releases energy and heat. It results in a rearrangement of atoms to form a different form of matter that wasn’t there before, in this case carbon dioxide and water (a chemical change). Sulfur is a very brittle solid. Brittleness is a physical property, since broken apart sulfur is still sulfur (a physical change)—the atoms have not rearranged themselves to express a new form of matter. In other words, it has not changed its composition. Another very important phenomenon influences matter, though it is not mater itself. Energy [Energy is the capacity to do work. Work, then, is when a force is applied over a given distance] can influence changes in matter, and in physical and chemical changes, energy is often exchanged with the surroundings. But it is important to keep in mind that energy is never actually created or destroyed—it merely changes form. This is known as the Law of Conservation of Energy. When something changes into something else, all the energy can be accounted for, and it doesn’t appear or disappear—it merely becomes incorporated within another process. All systems in the universe tend to move from a system of higher potential energy toward a system of lower potential energy, which often results in the release of energy into the surroundings. It’s like a ball—it will always roll downhill, and never uphill. Energy always works the same way and will follow the path of least resistance.

Definitions:

Chemical Property. A chemical property of a substance is a property that is displayed only when the substance changes its composition through a chemical change. An example is the flammability of gasoline.

Chemical Change. A chemical change is one that results from a rearrangement of atoms in matter. The original substance becomes a different substance, such as rusting:

(image credit: Pearson)

Physical Property. A physical property of a substance is a property that is displayed without a substance changing its composition. An example is the smell of gasoline:

Physical Change. A physical change is one that results in a change of state (i.e. liquid to gas) but not a change in composition (no rearrangement of atoms to become a new substance):

(image credit: Pearson)

Energy. The total energy is the sum of its kinetic energy (energy of motion) and its potential energy (energy of position or composition). Kinetic energy can be transformed into thermal energy, which is the energy associated with temperature:

(image credit: Pearson)

How Is It Relevant to You?

So, how is any of this relevant to your life? Everything is made of matter—you, the technology on which you are reading these words, the air you are breathing. If you can understand matter, you can better control it and interact with your environment in a more productive way to, for example, develop more and better medicines and technologies to increase the quality of life, develop better fuel and power sources, and myriad other applications. Chemistry helps understand why and under what circumstances reactions occur, why some substances exist as a liquid while others exist as a gas, and many other natural phenomena. Communication of findings is important, and it is extremely important that everyone understands one another’s claims and values, as well as any uncertainty associated with the values due to how the values were measured. Thus, accurate and precise measurement is paramount, and the degree of measurement reliability must be understood, so that others can evaluate the degree of certainty associated with the claims being made. Furthermore, unless a universal an international system of units is agreed upon and used, numbers become meaningless and confusing when many people begin communicating about the same topic. But to advance all of this knowledge, we have to operate through a logical and sequential system of thought, such as the scientific method. Once people started observing and understanding the world through this approach, knowledge began to grow exponentially. Just think about your own daily life…how much has it changed in the last 5-10 years as a result of science and its resulting technology? Finally, and perhaps more importantly, the more we understand how the universe works and is structured at the atomic level, the deeper the appreciation we can have

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