What is the Scale of Chemistry?
Chemistry is the study of matter and its transformations. Everything that you can taste, touch, see or smell is composed of chemicals. All the chemicals around you are made from various combinations of the elements on the periodic table. These elements can range considerably in size; specifically, atoms at the top of the periodic table are smaller than those near the bottom. The study of atoms and the reasons for the trend in their sizes will be covered in class later this semester.
Many of the chemicals we encounter everyday are molecular in structure. Molecules are specific combinations of atoms. The oxygen we breathe in and the carbon dioxide we breathe out are both molecular in their structure. The DNA and proteins that combine to make us are molecular compounds. The wood in the lab bench is mostly cellulose, a large organic molecule.
When choosing what unit to employ in a scientific measurement, it is important to consider both the size and type of measurement being made. For example, if one wants to discuss the length of a chemical bond in a molecule, one would use a distance unit. Since atoms are very small, it is convenient to use units such as pm (1 pm = 10−12 m) and Å (1 Å = 10−10 m). On the other hand, if one wishes to discuss the distance from Atlanta to New York, it may be more useful to use units such as m or km. If one wishes to describe the distance from earth to the sun, Mm (1 Mm = 106 m) or Gm (1 Gm = 109 m) may be more reasonable. Two scientists may choose to use different units to describe the same measurement; it is therefore important to be able to convert between different units in order to compare measurements. It is much easier to compare the relative sizes of two objects when they are described using the same units.
In this experiment, we will start our study of the scale of chemistry by using some standard tools to measure the dimensions of several small objects around the lab. We will then acquire some knowledge about the size of the chemicals around us by examining pictures and models of both familiar and unfamiliar chemical compounds. We will measure several dimensions of these molecules using computer generated models. Afterwards, we will compare the relative scales of the “small” objects found in the laboratory with the molecules we measured. Finally, we will complete a worksheet to review some basic math skills.
There are three objectives to this activity:
1. to become familiar with chemical models,
2. to emphasize how small chemicals are, and
3. to become more practiced using the metric system of units (especially distance units) and to practice using dimensional analysis in unit transformations.
Why Should I Care?
In this experiment we will become familiar with some computer-based chemical models and practice metric unit conversions. Why should we care about these topics?
The article below is a press report following the crash of NASA’s Mars Climate Orbiter in 1999. Read it and see why unit conversions are important in science! For a more positive view of NASA’s efforts to explore Mars go http://phoenix.lpl.arizona.edu/index.php. At this official site, read the news about Mars explorer Phoenix, which landed near the north pole of Mars in the summer of 2008 and sent back data about Martian soil until May of 2010. __________________________________________________________________________ Article 1: Unit Conversions
This is one of many press reports about the Mars Orbiter crash:
Contractor takes blame for math goof that crashed Mars probe
Make sure you have entries in your lab notebook for every item highlighted like this. These are the items your instructor will grade in your lab notebook.
Part 1: Small things
Create a table (a sample is provided below) in your lab notebook with the title “Table 1: Small Things Measurements”. (Tables should always have titles to specify their...
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