INTRODUCTION TO FORENSIC CHEMISTRY

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INTRODUCTION TO FORENSIC CHEMISTRY

• 1.1 Welcome
• 1.2 Chemistry, Crime, the Global Society
• 1.3 Physical Evidence Matter Its Forms
• 1.4 The Periodic Table
• 1.5 Learning the Language of Chemistry
• 1.6 The Most Important Skill of a Forensic
  Scientist Observation
• 1.7 Scientific Method
• 1.8 Case Study Finale Whose Side Are They
  On?

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INTRODUCTION TO FORENSIC CHEMISTRY

• Forensics means of the forum for public
  debates and trials can be introduced into legal
  procedings
• Forensic Science requires knowledge of biology,
  physics, geology, psychology, and chemistry, in
  particular, and more.
• Physical Evidence Matter Its Forms
• Matter exists as solids, liquids, or gases
• Liquids resist being compressed
• Gases are compressible

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The universe is composed of matter and energy.
Matter is composed of mixtures and pure
substances. In matter There are two kinds of
pure substances and two kinds of mixtures.
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1.3 PHYSICAL EVIDENCE MATTER AND ITS FORMS

• Matter is composed of mixtures and pure
  substances.
• Mixtures involve a physical blending of two or
  more pure substances.
• mixtures can be separated into their components
  by physical means such as evaporation or
  filtering
• Homogeneous mixtures have uniform properties and
  composition, for example, solutions (KoolAid).
• Heterogeneous - variable composition, and often
  show visible differences (Chocolate chip
  cookies).

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1.3 PHYSICAL EVIDENCE MATTER AND ITS FORMS

• Pure substances have uniform composition
  (elements and compounds)
• their components cant be separated by physical
  means such as distillation.
• Pure substances are composed of
• Elements. These contain only one type of atom.
  Fe, Na, As, etc.
• Compounds. These contain two or more types of
  atoms. H2O, NaCl, KNO3, etc.
• Compounds are of two types
• Molecular (covalent bonding), such as water,
  alcohol, sugar, or CO2.
• Ionic, such as salt, NaCl, or baking soda, NaHCO3.

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A lead (Pb) bullet, a homogeneous mixture,
contains traces of impurities such as bismuth,
Bi, and antimony, Sb.Add in the dirt here, and
the whole sample becomes a heterogeneous mixture.
Differences are usually visible.
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Can you sort the elements, compounds and mixtures?

• Identify each of these as a pure substance or a
  mixture
• then as either an element or a compound or as a
  homogeneous or heterogeneous mixture.

Pure a, b, d Element b Compound a, d Mixture
c, e Heterogeneous c Homogeneous e Solutions
are homogeneous. H2, Fe, salt water, wet sand
(SiO2), pure baking soda (NaHCO3), gasohol,
ice-water (s l).
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Introduction to the Periodic Table

• Symbols for the chemical elements are usually the
  first letter or the first and second or first and
  third letters.
• Examples include H for hydrogen, C for carbon, Ca
  for calcium, Zn for zinc, He for helium, and Mg
  for magnesium.
• Some elements were named by alchemists using
  Latin
• (These elements were known from antiquity.)
• Na for sodium, K for potassium, Au for gold, and
  Ag for silver, Sb for antimony.
• Hg for mercury, Fe for iron, Pb for lead, Cu for
  copper, Sn for tin, etc.
• Copper, silver, and gold still occur free in
  nature.
• You are responsible for knowing the symbol and
  name for elements 1-95.

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Introduction to the Periodic Table

• The table can be divided into metals, nonmetals,
  and metalloids.
• The metals predominate. They conduct heat and
  electricity well. Mercury is the only liquid at
  room temperature.
• The nonmetals are poor conductors, except for
  graphite, C.
• Metalloids include boron, silicon, germanium,
  arsenic, antimony, tellurium, polonium, and
  astatine. They conduct electricity at high
  temperatures.

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THE MOST IMPORTANT SKILL OF A FORENSIC SCIENTIST
Observation and the Scientific Method

• Observation is the most important skill
• It is the first step in the scientific method.
• It requires good judgment and experience to
  select the key evidence at a crime scene.
  Critical thinking is essential.
• It means being logical, rational, impartial, and
  analytical.

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• 2. How are gases characterized?
• A) By small distances between particles that are
  moving at low speeds
• B) By small distances between particles that are
  moving at high speeds
• C) By large distances between particles that are
  moving at low speeds
• D) By large distances between particles that are
  moving at high speeds
• 4. A molecule is defined as an atom.
•  A)True
•  B) False

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• 6. Sugar in tea is an example of what?
•  A) A complete mixture
•  B) An incomplete mixture
•  C) A heterogeneous mixture
•  D) A homogeneous mixture