chapter 2 science, systems, matter, and energy. models and behavior of systems usefulness of models...
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Chapter 2
Science, Systems, Matter, and Energy
MODELS AND BEHAVIOR OF SYSTEMS
Usefulness of models Complex systems are predicted by developing a
model of its inputs, throughputs (flows), and outputs of matter, energy and information.
Models are simplifications of “real-life”. Models can be used to predict if-then scenarios.
Feedback Loops: How Systems Respond to Change
Positive feedback loop causes a system to change further in the same direction (e.g. erosion)• the ice-albedo positive feedback loop whereby melting
snow exposes more dark ground which in turn absorbs heat and causes more snow to melt.
Negative (corrective) feedback loop causes a system to change in the opposite direction • predator-prey relationships in ecosystems.
Examples
Positive feedback – change continues in
one direction
Negative feedback – before one population grows exponentiallya feedback to reverse growth occurs
Time Delays
Corrective action of the negative feedback loop takes too long
TYPES AND STRUCTURE OF MATTER
Elements and Compounds Matter exists in chemical forms as elements and
compounds.• Elements (represented on the periodic table) are the
distinctive building blocks of matter.• Compounds: two or more different elements held
together in fixed proportions by chemical bonds.
Atoms
Figure 2-4
Ions
An ion is an atom or group of atoms with one or more net positive or negative electrical charges.
The number of positive or negative charges on an ion is shown as a superscript after the symbol for an atom or group of atoms Hydrogen ions (H+), Hydroxide ions (OH-) Sodium ions (Na+), Chloride ions (Cl-)
The pH (potential of Hydrogen) is the concentration of hydrogen ions in one liter of solution.
Figure 2-5
Compounds and Chemical Formulas
Chemical formulas are shorthand ways to show the atoms and ions in a chemical compound. Combining Hydrogen ions (H+) and Hydroxide
ions (OH-) makes the compound H2O (dihydrogen monooxide, a.k.a. water).
Combining Sodium ions (Na+) and Chloride ions (Cl-) makes the compound NaCl (sodium chloride a.k.a. salt).
Organic Compounds: Carbon Rules
Organic compounds contain carbon atoms combined with one another and with various other atoms such as H+, N+, or Cl-.
Contain at least two carbon atoms combined with each other and with atoms. Methane (CH4) is the only exception. All other compounds are inorganic.
Organic Compounds: Carbon Rules
Hydrocarbons: compounds of carbon and hydrogen atoms (e.g. methane (CH4)).
Chlorinated hydrocarbons: compounds of carbon, hydrogen, and chlorine atoms (e.g. DDT (C14H9Cl5)).
Simple carbohydrates: certain types of compounds of carbon, hydrogen, and oxygen (e.g. glucose (C6H12O6)).
Cells: The Fundamental Units of Life
Cells are the basic structural and functional units of all forms of life. Prokaryotic cells
(bacteria) lack a distinct nucleus.
Eukaryotic cells (plants and animals) have a distinct nucleus.
Figure 2-6
Macromolecules, DNA, Genes and Chromosomes
Large, complex organic molecules (macromolecules) make up the basic molecular units found in living organisms. Complex carbohydrates Proteins Nucleic acids Lipids
Figure 2-7
States of Matter
The atoms, ions, and molecules that make up matter are found in three physical states: solid, liquid, gaseous.
A fourth state, plasma, is a high energy mixture of positively charged ions and negatively charged electrons. The sun and stars consist mostly of plasma. Scientists have made artificial plasma (used in
TV screens, gas discharge lasers, florescent light).
Matter Quality
Matter can be classified as having high or low quality depending on how useful it is to us as a resource. High quality matter is
concentrated and easily extracted.
low quality matter is more widely dispersed and more difficult to extract.
Figure 2-8
CHANGES IN MATTER Matter can change from one physical form to
another or change its chemical composition. When a physical or chemical change occurs, no
atoms are created or destroyed.• Law of conservation of matter.
Physical change maintains original chemical composition.
Chemical change involves a chemical reaction which changes the arrangement of the elements or compounds involved.• Chemical equations are used to represent the
reaction.
Chemical Change
Energy is given off during the reaction as a product.
p. 39
Reactant(s) Product(s)
carbon + oxygen carbon dioxide + energy
C + O2 CO2 energy+
energy+
black solid colorless gas colorless gas
+
Types of Pollutants
Factors that determine the severity of a pollutant’s effects: chemical nature, concentration, and persistence.
Pollutants are classified based on their persistence: Degradable pollutants Biodegradable pollutants Slowly degradable pollutants Nondegradable pollutants
ENERGY
Energy is the ability to do work and transfer heat. Kinetic energy – energy in motion
• heat, electromagnetic radiation Potential energy – stored for possible use
• batteries, glucose molecules
Electromagnetic Spectrum
Many different forms of electromagnetic radiation exist, each having a different wavelength and energy content.
Figure 2-11
Electromagnetic Spectrum
Organisms vary in their ability to sense different parts of the spectrum.
Figure 2-12
Fig. 2-13, p. 44
Low-temperature heat (100°C or less) for space heating
Moderate-temperature heat (100–1,000°C) for industrial processes, cooking, producing
steam, electricity, and hot water
Very high-temperature heat (greater than 2,500°C) for industrial processes and producing electricity to run electrical devices (lights, motors)
Mechanical motion to move vehicles and other things) High-temperature heat (1,000–2,500°C) for industrial processes and producing electricity
Dispersed geothermal energyLow-temperature heat (100°C or lower)
Normal sunlightModerate-velocity windHigh-velocity water flowConcentrated geothermal energyModerate-temperature heat
(100–1,000°C)Wood and crop wastes
High-temperature heat (1,000–2,500°C)Hydrogen gasNatural gasGasolineCoalFood
ElectricityVery high temperature heat (greater than 2,500°C)Nuclear fission (uranium)Nuclear fusion (deuterium)Concentrated sunlightHigh-velocity wind
Source of Energy RelativeEnergy Quality
(usefulness)
Energy Tasks
Laws of Thermodynamics
First Law: energy cannot be created or destroyed, but it can be transformed from one form to another
Sunlight chemical energy food(photosynthesis)
Second Law: when energy is transformed, it is degraded to lower quality
Gasoline combustion in car mechanical energy + heat