Lecture Notes
Thanatochemistry
Week 1
Introduction
The standard definition of chemistry is the study of:
1. The nature of matter
2. The changes that matter undergoes
To understand this definition we must first define matter. MATTER is anything
that occupies space and possesses mass. The word mass is used here instead
of weight. Mass is the amount of "stuff" a substance possesses. Weight is a
measure of gravitational forces.
The nature of matter can mean two things:
1. The composition of that matter
2. The forces holding that matter together.
For example: Water is composed of Hydrogen and Oxygen. The oxygen and
hydrogen are held together by a chemical bond. The chemical bond is the result
of interactions between the nuclei of the two elements.
The changes that matter undergoes can be classified as:
1. Physical
2. Chemical
A PHYSICAL CHANGE is one which does not alter the chemical composition of
the material. The melting of ice is a good example of a physical change.
The chemical composition of both ice and water is H2O.
A CHEMICAL CHANGE results in the formation of new substance. The
decomposition of water when an electric current is passed through it is
an example. The composition of water is H2O. After the current is passed
through it we now have O2 and H2.
Accompanying physical and chemical changes are energy changes, which are
some of the most important types of changes that matter undergoes.
ENERGY is defined as the ability to do work and can be divided into:
1. POTENTIAL ENERGY
2. KINETIC ENERGY
POTENTIAL ENERGY is energy which is inherent in a system. Batteries
have potential energy. They have energy in them which has the
"potential" to make the toy run. Chemical substances have
chemical energy which is a form of potential energy. This energy
is released during chemical reactions.
KINETIC ENERGY is energy of motion. The energy released as a ball
rolls across the floor is a form of kinetic energy.
DIVISIONS OF CHEMISTRY
The three major divisions of chemistry are:
1. Organic
2. Inorganic
3. Biochemistry
We will also be studying embalming chemistry.
Let us first start by defining ORGANIC CHEMISTRY. Originally organic
chemistry was the study of compounds that could be produced only by living
organisms. This definition was found to be in error in 1828 when Wohler
synthesized urea, a compound normally produced by animals. He did this by
heating a nonliving compound called ammonium cyanate.
Heat + NH4+NCOAmmonium Urea
Cyanate
Since the time of Wohler, ORGANIC CHEMISTRY has been defined as the
study of certain carbon containing compounds. BIOCHEMISTRY is the term
used for the study of substances produced by living organisms. INORGANIC
CHEMISTRY is the study of minerals and other inanimate materials commonly
found in the earth. The study of Inorganic chemistry includes carbon monoxide,
carbon dioxide, the carbonates and the bicarbonates even though they contain
carbon.
EMBALMING CHEMISTRY is the study of those types of matter and changes in
matter related to the disinfection and preservation of a human remains.
CHEMICAL MEASUREMENTS
Chemists are involved in making measurements of physical quantities, of which
we will consider four: length, volume, mass, and heat. Each quantity has a
standard unit in the metric system and divisions and multiples of the standard
that are based on graduations of ten.
Table of prefixes used in measurements
deci 1/10 = 0.1
centi 1/100 =0.01
milli 1/1000=0.001
micro 1/1,000,000 =0.000001
deca 10
hecto 100
kilo 1000
mega 1,000,000
LENGTH
The standard unit of length is the meter(m). 1 meter(m) = 10 decimeter(dm) =
100centimeters(cm) = 1000 millimeters (mm).
1000meters(m) = 1 kilometers(km).
(The letters in parenthesis represent the appropriate abbreviations for that
measurement.)
VOLUME
The standard unit of volume is the liter(l). One other important volume unit is
the milliliter(ml). There are l000 ml in one liter. The milliliter is sometimes called
a cubic centimeter (cc). A cube having a length, width, and height each equal to
one centimeter has a volume of one cubic centimeter. Since one milliliter of
water will fill this cube at 4o
centigrade, it is consistent to say that one milliliter equals one cubic centimeter.
1ml = 1cc.
MASS
The standard unit of mass is the kilogram (kg). Smaller units of mass are the
gram (g) and the milligram (mg). 1kg = 1000g and 1g = 1000mg.
HEAT
The standard unit of measurement for heat is the calorie (cal). The calorie is
defined as the quantity of heat necessary to raise the temperature on one gram
of water 1o centigrade at 15o centigrade. In metabolic processes the calorie is
often too small a unit, the kilocalorie(Kcal) is used. The kilocalorie is equal to
1000 calories. The kilocalorie is also symbolized as Cal. 1Kcal = 1Cal =
1000cal.
CONVERTING BETWEEN MEASUREMENTS
Sometimes in the chemistry lab we are given measurements that need to be
converted to other measurements before we can proceed with our experiments.
The stairs below are an easy way to do this.
First example: I have 10.0 liters of a liquid, and I need to determine how many
milliliters I have.
Liter is three steps to the right of the Milli. Therefore, I move my decimal point
three steps to the right. My 10.0 liters becomes
10,000 ml.
Second example: I have 1000.0 ml, and I need to determine how many kiloliters
I have.
Milli is six steps to the left of kilo. Therefore I move my decimal point six steps
to the left. My 1000.0 ml becomes .001 kl.
WEEK 1
PHYSICAL AND CHEMICAL CHANGES
PHYSICAL PROPERTIES
PHYSICAL PROPERTIES are characteristics that can be observed without
altering the chemical composition of a substance.
Typical physical properties are:
1. Odor
2. Color
3. Taste
These all describe what a substance IS. For example: A lemon is yellow and is
sour.
Another common physical property is the STATE in which a type of matter
exists at a given temperature and pressure.
We are familiar with the three states of water: ice, liquid water and water vapor
or steam. In each state water’s chemical composition is the same,
but the physical characteristics are different.
Some other examples of physical properties include a substance’s MELTING
POINT and BOILING POINT, its SOLUBILITY in other substances, and its
DENSITY and SPECIFIC GRAVITY.
The melting point of a substance is that temperature at a given pressure at
which a substance changes from the solid state to the liquid state. For pure
water themelting point is 32oF or 0oC.
The Freezing point of a substance is the same as the melting point, since the
process of freezing is the opposite of melting.
The boiling point is defined as that temperature at which a substance changes
from the liquid state to the gaseous state. This property is also pressure
dependent. For pure water at a pressure of one atmosphere the boiling point is
212oF or 100oC. If the atmospheric pressure is decreased such as on a
mountain top, water will boil at a lower temperature.
All substances have their own characteristic melting and boiling points as
measurable physical properties which can be used to identify them.
Another physical property of a substance is its Solubility. We can measure the
amount of salt that will dissolve in a given amount of water. If we do this we are
measuring the physical property of solubility. The salt and water do not
chemically react. The salt is simply dissolved in the water.
Density is another quantitative physical property. Density expresses the
relationship between mass and volume and can be mathematically defined as:
D=M/V.
The normal density units for solids and liquids are grams/milliliter and the units
for gases are usually grams/liter. In the lab densities are determined by a
procedure known as displacement of water. The technique can not be used
with solids that dissolve in water. All substances have a specific density by
which they can be identified. Pure water has a density of 1g/ml because one
gram of purewater occupies a volume of 1ml at 4oC.
Examples: If 10 grams of a substance occupies a volume of 2ml, what is the
density of the substance?
D= 10g/2ml=5g/ml
A test tube has 10ml of water in it. After placing 30g of our substance in the test
tube, the new water level reads 20ml. What is the density?
We first need to determine the volume that the substance occupies.
Volume = 20ml - 10ml = 10ml
So Density = 30g/10ml = 3g/ml
A physical property that is closely related to density is Specific gravity. For
liquids and solids, this property is the ratio of the mass of the substance to the
mass of an equal volume of water at the same temperature.
Specific Gravity = mass of the solid or liquid
mass of an equal volume of water
Specific gravity is a ratio and has no units.
CHEMICAL PROPERTIES
CHEMICAL PROPERTIES are characteristics which can be observed when the
substance is interacting with other forms of matter. Chemical properties tend to
define what a substance does. The interaction results in an alteration of the
chemical composition of the substance. When iron is exposed to the air it
chemically reacts with the oxygen to form iron oxide (rust). This is a chemical
change because we now have different chemical substances than those which
we started with. Not all substances simply dissolve in water. Some substances
such as sodium will chemically react with the water.
2Na + 2H2O
2NaOH + H2
Notice that we end up with completely different substances than those with
which we started.
PHYSICAL AND CHEMICAL CHANGES
A PHYSICAL or a CHEMICAL CHANGE is a process that manifests either a
physical or chemical property.
Common physical changes are changes in state. For example, when ice melts
we can observe water’s physical properties. Another common physical change
is dissolving one substance in another such as salt in water. Evaporation of the
water from the salt demonstrates that dissolving is a physical change, because
the original solid salt is still present after the evaporation of the water.
Chemical changes form new substances with their own chemical and physical
properties. Some examples of chemical changes are rusting of iron, burning of
paper, and souring of milk. Chemical changes of importance to the embalmer
are cremation of remains, decomposition, and embalming of remains.
When iron rusts, it unites with oxygen in the air, forming iron oxide. An OXIDE is
a substance containing two elements, one of which is oxygen. Whenever
matter is burned in the presence of oxygen oxides are produced. Another name
for this chemical change is COMBUSTION. This also occurs when remains are
cremated.
The breakdown of biochemical compounds into smaller, units is initiated by a
process called HYDROLYSIS. This process involves water reacting with the
substance and is also a chemical change. The embalming process attempts to
disinfect and preserve human remains, thereby slowing the rate of this chemical
change.
Lecture Notes