Chapter # 4
Environnemental Science.
Interrelated Scientifique Principales : Mater, Energy and Environnent.
Out line
Intro to the concepts of matter and energy; how changes in the nature of
Matter and in the use of energy affect living things and human societies.
Early thinking – Superstitious/ Supernatural
The Nature of Science
Scientific Method
Method
Cause and Effect Relationships
Pitfalls/ Limitations
Pseudoscience
Structure of Matter
Definition
Atoms- Nucleus/ Electrons/ Isotopes/ Ions.
Molecules
Bonding – molecules
Compounds
Mixtures
Water
Compounds – Characteristics determined by types of bonds
ACIDS/BASES
PH scale
Organic – Carbon atoms; manufactured from inorganic; chemical
energy released
Inorganic matter- few
Bonds holding atoms: Broken/ Formed = Chemical Reactions
Energy released = Exothermic
Stored = Endothermic
Reaction started = Activation – controlled by catalyst
Catalyst = Enzymes.
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Examples: Water + CO2 + Light = Sugar + Oxygen (Photosynthesis)
Organic molecules+ O2 = CO2 + Energy (Respiration)
Chemistry in the Environment.
Energy Principles
Types of Energy
States of Matter
Sensible heat transfer (Temp changes)
Latent heat transfer
Laws of Thermodynamics (2) / Implications of Energy Flow.
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NATURE OF SCIENCE
Environmental Science is a relatively new discipline that includes:
1. Applied and theoretical science (The social, Economic and Political
aspects).
Science – how knowledge is acquired, rather than what is studied.
How data are collected and analyzed
A process used to solve problems or to develop an understanding of
nature. It involves testing possible answers.
In order to make responsible environmental related decisions and to
appreciate the ecological concepts, it is necessary therefore to understand
some chemical and Physical principles.
.
Basic assumptions in science
Scientific Method is a way of getting info by forming possible solutions to
questions followed by rigorous testing to determine if the solutions are valid
One assumes that the fundamental rules of nature apply regardless of where
and when they occur.
Cause and Effect Relationships
Many events happen at the same time, but not all show a cause and effect
relationship.
Knowing that a cause and effect relationship exist, enables us to predict what
will happen should that same set of circumstances occur in the future
Elements of the Scientific Method .
1. Make observations, accurate and unbiased. Question literature.
2. Develop a hypothesis based on observations and information, a
logical best guess to explain the observations.
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3. Test hypothesis by making additional observations or experiment;
must be testable to prove a fact.
4. Modify the hypothesis if necessary
5. Prove hypothesis by repeating experiment. Publishing is most
important
6. Theory, a broad concept – published. Later a Law, a constant or
uniform fact of nature that describes what happens in nature.
These steps are not inflexible
Theories are broadly written statements. (The word is not always used in the
strict scientific sense).
Possible Pitfalls
Problem definition
Data collection
Development of a hypothesis.
LIMITS to the METHOD
Applicable only to science
Results are not always correct due to faulty or inadequate data
Not suitable for over generalization
Not suitable for predictions
Conclusions can be used to support both valid and invalid
conclusions.
PSEUDOSCIENCE.
Facts are selected to support a specific point of view.
STRUCTURE of MATTER
Matter is anything that takes up space and has weight.
The best way to describe matter is by using the KINETIC MOLECULAR
THEORY, which is that all mater is composed of tiny particles (ATOMS)
that are in constant motion.
Atomic Structure
Atoms are the fundamental subunits composed of PROTONS, NEUTRONS
and ELECTRONS.
Each atom has a central region, a NUCLEUS. The nucleus consists of 2
types of heavy particles PROTONS (+) and NEUTRONS
Clouds of light-weight, fast moving (-) charged ELECTRONS surround the
nucleus.
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The Number of protons, neutrons and electrons in an atom is the difference
between elements (92 in all). All atoms of the same element may not have
the same number of neutrons, in which case those are ISOTOPES, which
have the same # of protons and electrons.
Molecular Nature of Matter
Atoms bonded together into a stable unit is a molecule, but when different
atoms are bonded, a COMPOUND is formed. There are many ways atoms
can be combined to form compounds.
Mixtures are a combination of atoms or molecules
An atom or molecule that has lost or gained one or more electrons is an ION.
A Word about Water
It covers about 72% of the earth’s surface, influences weather and climate.
Present in all living things. Exist in gas, liquid and solid form on earth. It is
a di-polar molecule, responsible for its property as a universal solvent
Acids, Bases and pH (acetic acid, vinegar, Sulfuric acid)
A class of compounds, whose characteristics are determined by the type of
bonds . Acids in water release H+ ions. The acids attract negatively charged
particles.
Bases are the opposite. They release Hydroxyl ions (OH-) in a solution or
accept H ions. Sodium Hydroxide or oven cleaner is an example of a base –
an alkaline solution.
The acid or base strength is represented by a number called its pH, which
measures H+ concentration. The number 7 represents a balance between H
and OH ions. An increasing number (of H ions) is represented by a smaller
pH. Scale is 1 – 14 (Logarithmic and reciprocal)
Inorganic and Organic matter.
Organic matter contains CARBON atoms, bonded into large molecules
(sugar, protein, fat) each of which contains large amounts of chemical
energy, released when broken down into inorganic molecules.
Inorganic matter composed of small inorganic molecules, are relatively few
types (salt, water, Oxygen, and metals).
Living things can manufacture organic molecules from inorganic molecules
or they can modify organic molecules by consuming organic matter.
Chemical Reactions
When combined in a molecule, Atoms are held together by chemical
BONDS (the interaction between electrons). When the bonds are formed or
broken, a CHEMICAL REACTION occurs, at which time energy is released
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(LOST) as heat or light in an exothermic reaction, or stored in an
endothermic reaction.
To bond or break apart a molecule, it is necessary to put energy into the
system. That energy is ACTIVATION ENERGY.
The amount of activation energy is controlled by CATALYSTS. A catalyst
is a substance that alters the rate of a reaction, but it is not altered.
Chemical reactions in living things
Catalysts (in living things) are enzymes. ENZYMES are proteins, which
serve to reduce the activation energy needed to start a reaction or to lower
the temperature at which the reaction occurs.
Example: Photosynthesis is a process in which inorganic material is
converted to organic using light energy. Water and Carbon Dioxide are
changed to Sugar and Oxygen is released.
In RESPIRATION, oxygen is used to break down organic molecules (sugar)
into inorganic. (Carbon Dioxide and energy is released).
Chlorophyll is responsible for trapping the sunlight energy in the
photosynthesis process.
Chemistry is extremely important in Environmental problems. (Fertilizers
and Pesticides, Smog and Water.
Chemistry in the Environment
Chemicals are common in the environment. Present in insecticides,
(pesticides) and fertilizers. They play a very important role in food
production. Organic molecules in water reduce the Oxygen available to
living things,
ENERGY PRINCIPLES
Energy and matter are inseparable.
Energy is the ability to do work, move matter over a distance.
Kinds of Energy
The energy in moving objects is called KINETIC. eg. In air, the molecules
are in constant motion
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POTENTIAL energy is special. It is the energy in an object resulting from
the position of the object.
Several other types of energy abound. (Heat, light, electrical, chemical). It is
possible to convert one form into another.
States of Matter
The state in which matter occurs depends on the amount of energy in the
matter. If the amount of Kinetic energy is changed, the physical nature of the
matter changes. The CHEMICAL nature stays unchanged. Eg. Water.
Sensible heat transfer: when two objects placed next to each other, the cool
object becomes warm and the hot one gets cooler.
Latent heat transfer: When heat energy is used to change the state of matter,
heat is transferred, but the Temperature of the object does not change.
Laws of Thermodynamics
1. Energy cannot be created or destroyed. It can only be converted from one
form to another.
2. There is no loss in total energy in conversion, but there is some loss in
useful energy.
The energy that cannot be used to do useful work is called entropy. Entropy
increases on converting energy.
ENVIRONMENTAL IMPLICATIONS of ENERGY FLOW.
Energy Entropy : When energy is converted, the lost energy is dissipated
into the universe (entropy)
Energy Quality: Some forms of energy are high quality (electricity) and
others are of low quality. Eg. Heat in Ocean waters.
Biological Systems and Thermodynamics : All organisms are in the process
of converting energy, low to high, but quantity stays the same.
Pollution and Thermodynamics : Chemical energy in food is converted to
be used in growth or to do work- respiration. This is similar to combustion.
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The consequence of energy conversion is POLLUTION.
The heat lost is waste, a pollutant.
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