Category Archives: Chemistry Review

Lecture 17 – Review of Scientific Notation


In preparation for an intense study of bone structure, bone density, and the significance of the body’s minerals, I promised a review of scientific notation.  Scientific notation is a simple way of writing and keeping track of large and small numbers without a lot of zeros.  It also provides a shortcut to recording results and doing calculations.

Example 1- Large Numbers:

100 equals  (10)(10)                                                  or 102                  or one hundred

1,000 equals  (10)(10)(10)                                            or 103                  or one thousand

10,000 equals  (10)(10)(10)(10)                                     or 104                  or ten thousand

100,000 equals  (10)(10) (10)(10)(10)                                 or 105                    or one hundred

thousand

1,000,000 equals  (10)(10)(10)(10)(10)(10)                        or 106                     or one million

1,000,000,000 equals  (10)(10)(10)(10)(10)(10)(10)(10)(10)   or 109                   or one billion

The best technique is to just commit this to memory.  Use Post-It notes attached to your bathroom mirrors if you have to.  I am constantly reviewing as I apply my make-up.  Pick up a hand held recording device and read this information aloud.  Hearing information in your own voice is quite effective.

Example 2 – Small Numbers:

1/10                 equals 10-1                                                                                                   or one tenth

1/100               equals 1/(10)(10)                                                      or 10-2                     or one hundredth

1/1,000            equals 1/(10)(10)(10)(10)                                         or 10-4                   or one ten thousandth

1/1,000,000     equals 1/(10)(10)(10)(10)(10)(10)                            or 10-6               or one millionth

1/100,000,000 equals 1/(10)(10)(10)(10)(10)(10)(10)(10)(10)        or 10-9               one billionth

Here are some everyday metric measurements. Metric measurements can describe different scale objects.

Sample                                                                                               Measurements (Meters)

Diameter of Uranium Nucleus                                                            10-13

H2O Molecule                                                                                          10-10

Protozoa                                                                                                   10-5

Earthworm                                                                                              10-2

Human                                                                                                     2

Mount Everest                                                                                        103

Diameter of the Earth                                                                           107

Distance from Pluto into Sun                                                              1013

Significant Figures

Measurements may not be exact, but as medical scientists, we try to record the answers with the least amount of uncertainty.  The idea of scientific notation was set up to standardize measurements with the least uncertainty.  Significant figures were used in order to write numbers either in whole units or to the highest level of confidence.

Significant figures are the number of digits written after the decimal point to measure quantity.

A counted significant figure cannot be divided into sub-parts.  These are recorded in whole numbers such as 10 tubes of lipstick, 9 containers of eye shadow, or 7 bottles of foundation.  (Does anybody still use Fashion Fair?  I like Warm Honey.  Fashion Fair and Clinique were the most popular department store cosmetics of my teen years.  I think MAC or Prescriptives might hold that title now.)  Bear with us, Gentlemen.  So many careers have been boys’ clubs for so long, I have to make this fun for the girls!

Now, just relax as we do a few examples.  If you know this well, re-read for good measure.  Over-learning is also a good technique.  Your eyes can never look at good information too many times!  If this is a weak area for you, do not rush through it.  Your future patients need you to grasp each intricate concept.  Medication errors do not have to happen!

How many significant figures are in the following?  Check out the bold hints!

  1.  9.107   (4, because zeros in the middle are significant.)
  2. 401       (3, because the zero in the middle is significant.)
  3. 0.006    (1, because leading zeros are never significant.)
  4. 800 km (3, zeros are significant in measurements unless otherwise indicated.  Note: These zeros follow a non-zero number.)
  5. 3.002 m (4, because zeros in the middle of non-zero digits are significant.)

More Tips:

When finding out the number of significant figures, the easiest shortcut is to look at the zeros acting as placeholders.

Leading zeros at the beginning (or the left-hand side) of a number are never significant.  Start at the left and count to the right of the decimal point.  The measurement 0.096 m has two significant figures.  The measurement 13.42 cm has four significant figures.  The mass 0.0027 has two significant figures.  (Remember to leave off the leading zeros.)

Zeros sandwiched in the middle of non-zero numbers are always significant.  The number 26,304 has five significant figures.  The measurement 0.000001002 m has four significant figures.

In summary, scientific notation gets rid of the guessing and helps to keep track of zeros in very large and very small numbers.  If the diameter of Earth is 10,000,000 m, it is more practical to write 1 X 107 m.  Or, if the length of a virus is 0.000000004 m, it is easier to write 4 X 10-8 m.  Remember to ‘go through the hard parts’.  It will get easier.  It is necessary to review measurements before moving on to bone density and other anatomic slides that reference complex measurements.  You will need a command of measurements as you progress in your career.  Do well with this information.  We are building a solid foundation.

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Lecture 12 – Part 2 of Review Power


Chemistry is an experimental science and is divided into two branches, pure chemistry and applied chemistry.  Pure chemistry is theoretical and predicts results of experiments or observations.  Applied chemistry involves the practical applications of materials and reactions.  How does soap made from ashes and fat get clothes clean?  How do computer chips made of silicone (sand) carry information and electricity?

A hypothesis is a statement or idea that describes or attempts to explain observable information.

An experiment is a controlled testing of the properties of a substance or system through carefully recorded measurements.

Let’s review some key points in the history of science.  Capernicus believed that from the sun outwards, rotated Mercury, Venus, Earth (with the moon rotating around it), Mars, Jupiter, and Saturn.  This strange hypothesis was not received well since everyone knew that the sun revolved around the earth.  In 1609, Galileo used his homemade telescope to test Capernicus’ hypothesis.  Galileo took measurements and recorded data that confirmed Capernicus’ hypothesis.  In doing so he discovered the key to valid research was experimentation.  His scientific curiosity caused him to record observations regarding changing factors, such as time, position of moon, stars, and sun.  These observations and calculations led to the discovery of the four satellites of Jupiter in 1610.  Galileo’s scientific diligence is why we consider him the founder of the scientific method.

Antoine Lavoisier (1743-1794) insisted on accurate measurements and developed a theory of combustion.  He determined that combustion results from a chemical bonding between a burning substance and a component of the air, which he named oxygen.  The bonding of these two forms something new.  Joseph Priestly and Antoine Lavoisier performed experiments together and discovered that the air was composed of several different components, including nitrogen.  Previously it was thought that air was composed of one all-purpose gas.  Lavoisier found that water contained hydrogen and oxygen.  He was the first to arrange chemicals into a family of groups, and the first to attempt to explain why some chemicals form new compounds when mixed.  This is why he is considered the father of modern chemistry.

A theory is the result of thorough testing and confirmation of a hypothesis.  It predicts the outcome of new testing based on previous experimental data.

A law is a hypothesis or theory that is tested time after time with the same resulting data and thought to be without exception.

John Dalton made significant contributions to chemistry by:

Developing the Law of Partial Pressures in 1803;

developing the atomic theory (his most important discovery);

developing the law of multiple proportions;

publishing a list of atomic weights and symbols.  (This gave chemistry its initial formal vocabulary, which we memorize today.)

APPLICATIONS FOR EVERYDAY

In case you are wondering why I am giving such a detailed background in chemistry, I will relieve your mind.  Chemistry is a part of our daily lives, as we cook, clean, breathe, and go about our activities.  NASA, the National Aeronautical and Space Administration is famous for applying basic science in new ways.  NASA uses the scientific method teams with scientists in industry to improve pharmaceuticals, optics, and bioengineering devices.  Dual purpose science and technology brainstorms are called spinoffs.

Examples:

1)      Medical Gas Analyzer – Astronaut physiological monitoring technology; Used to measure operating room anesthetic concentrations, such as oxygen, carbon dioxide, and nitrogen; Ensures precise breathing environments for surgery patients.

2)      Bioreactor-  A cell culture device developed at NASA – Johnson Space Center that brings a new scientific tool to cancer and virus testing without risking harm to patients.  The rotating bioreactor walls allow three-dimensional growth of tissues without limiting pressure points.  It has successfully cultured over 35 cell types.

3)      Low Vision Enhancement System – Provides a video scene via a system of optical mirrors that project video images onto the wearer’s retinas.  The goggle-like headset help counteract the effects of macular degeneration associated with aging, diabetic retinopathy, glaucoma, and tunnel vision.

A wide variety of elements are found in the body.  These elements combine to keep our bodies healthy.

Oxygen                                                 64.6%

Carbon                                                 18%

Hydrogen                                             10%

Nitrogen                                               3.1%

Calcium                                                1.9%

Phosphorus                                          1.1%

Chlorine                                               0.4%

Potassium                                            0.36%

Sulfur                                                    0.25%

Sodium                                                 0.11%

Magnesium                                          0.03%

Iron                                                        0.005%

Copper                                                   0.0004%

Tin                                                          0.0001%

Manganese                                           0.0001%

Iodine                                                  0.0001%

Others Trace Elements Combined        0.14%

Elements Found on Earth

Oxygen (O)                                                   49.2%

Silicon (Si)                                                      25.7%

Aluminum (Al)                                                7.5%

Iron (Fe)                                                           0.005%

Calcium (Ca)                                                    1.9%

Manganese (Mn)                                            0.0001%

Tin (Sn)                                                             0.0001%

Phosphorus (P)                                                1.1%

Chlorine (Cl)                                                     0.4%

Potassium (K)                                                   0.36%

Sulfur (S)                                                           0.25%

Magnesium (Mg)                                             0.03%

Sodium (Na)                                                     0.11%

Iodine                                                                 0.0001%

Zinc (Zn)                                                            0.002%

Copper (Cu)                                                       0.0004%

Others Cumulatively                                        0.47%

So, what do these elements do for us?

Element                                                              Function in the Body

Calcium                                                               Bones, teeth, and body fluids

Phosphorus                                                        Bones and teeth

Magnesium                                                         Bones and body fluids; energy

Sodium                                                                Cellular fluids; transmission of nerve impulses

Chloride                                                               Dissolves salt in extracellular and stomach fluids

Potassium                                                            Cellular fluids and transmission of nerve impulses

Sulfur                                                                    Amino acids and proteins

Iron                                                                       Hemoglobin, muscles, and stored in organs

I hope you are finding the background information helpful.  We all have gaps and inconsistencies in our knowledge.  One of my goals has always been to fill in the educational gaps.  More than ever I am seeing liberal arts majors applying to medical school.  So many have extensive knowledge in other fields.  Intense review of the sciences is extremely important for the student doctor who majored in chemistry as an undergraduate, as well as the English major who decided that medicine is the new art form.  Now we are better equipped to continue our intense survey of human bones.  Make it a great day!

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