Chapter 2 Science, Systems, Matter, and Energy

Feedback Loops: How Systems Respond to Change  Outputs of matter, energy, or information fed back into a system can cause the system to do more or less of what it was doing. Positive feedback loop causes a system to change further in the same direction (e.g. erosion) Positive feedback loop causes a system to change further in the same direction (e.g. erosion) Negative (corrective) feedback loop causes a system to change in the opposite direction (e.g. seeking shade from sun to reduce stress). Negative (corrective) feedback loop causes a system to change in the opposite direction (e.g. seeking shade from sun to reduce stress).

Feedback Loops:  Negative feedback can take so long that a system reaches a threshold and changes. Prolonged delays may prevent a negative feedback loop from occurring. Prolonged delays may prevent a negative feedback loop from occurring.  Processes and feedbacks in a system can (synergistically) interact to amplify the results. E.g. smoking exacerbates the effect of asbestos exposure on lung cancer. E.g. smoking exacerbates the effect of asbestos exposure on lung cancer.

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 (CH 4 ) is the only exception. Methane (CH 4 ) is the only exception. All other compounds are inorganic. All other compounds are inorganic.

Organic Compounds: Carbon Rules  Hydrocarbons: compounds of carbon and hydrogen atoms (e.g. methane (CH 4 )).  Chlorinated hydrocarbons: compounds of carbon, hydrogen, and chlorine atoms (e.g. DDT (C 14 H 9 C l5 )).  Simple carbohydrates: certain types of compounds of carbon, hydrogen, and oxygen (e.g. glucose (C 6 H 12 O 6 )).

States of Matter  The atoms, ions, and molecules that make up matter are found in three physical states: solid, liquid, gaseous. 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. The sun and stars consist mostly of plasma. Scientists have made artificial plasma (used in TV screens, gas discharge lasers, florescent light). Scientists have made artificial plasma (used in TV screens, gas discharge lasers, florescent light).

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. When a physical or chemical change occurs, no atoms are created or destroyed. Law of conservation of matter.Law of conservation of matter. Physical change maintains original chemical composition. Physical change maintains original chemical composition. Chemical change involves a chemical reaction which changes the arrangement of the elements or compounds involved. 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 equations are used to represent the reaction.

Chemical Change  Energy is given off during the reaction as a product.

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 Degradable pollutants Biodegradable pollutants Biodegradable pollutants Slowly degradable pollutants Slowly degradable pollutants Nondegradable pollutants Nondegradable pollutants

Nuclear Changes: Radioactive Decay  Natural radioactive decay: unstable isotopes spontaneously emit fast moving chunks of matter (alpha or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. Radiation is commonly used in energy production and medical applications. Radiation is commonly used in energy production and medical applications. The rate of decay is expressed as a half-life (the time needed for one-half of the nuclei to decay to form a different isotope). The rate of decay is expressed as a half-life (the time needed for one-half of the nuclei to decay to form a different isotope).

Nuclear Changes: Fission  Nuclear fission: nuclei of certain isotopes with large mass numbers are split apart into lighter nuclei when struck by neutrons. Figure 2-9

Uranium-235 Fig. 2-6, p. 28 Neutron Uranium-235 Energy Fission fragment Fission fragment n n n n n n Energy Stepped Art

Nuclear Changes: Fusion  Nuclear fusion: two isotopes of light elements are forced together at extremely high temperatures until they fuse to form a heavier nucleus. Figure 2-10

ENERGY  Energy is the ability to do work and transfer heat. Kinetic energy – energy in motion Kinetic energy – energy in motion heat, electromagnetic radiationheat, electromagnetic radiation Potential energy – stored for possible use Potential energy – stored for possible use batteries, glucose moleculesbatteries, glucose molecules

Electromagnetic Spectrum  Many different forms of electromagnetic radiation exist, each having a different wavelength and energy content. Figure 2-11

ENERGY LAWS: TWO RULES WE CANNOT BREAK  The first law of thermodynamics: we cannot create or destroy energy. We can change energy from one form to another. We can change energy from one form to another.  The second law of thermodynamics: energy quality always decreases. When energy changes from one form to another, it is always degraded to a more dispersed form. When energy changes from one form to another, it is always degraded to a more dispersed form. Energy efficiency is a measure of how much useful work is accomplished before it changes to its next form. Energy efficiency is a measure of how much useful work is accomplished before it changes to its next form.

Fig. 2-14, p. 45 Chemical energy (food) Solar energy Waste Heat Waste Heat Waste Heat Waste Heat Mechanical energy (moving, thinking, living) Chemical energy (photosynthesis)

Sustainable Low-Throughput Economies: Learning from Nature  Matter-Recycling-and-Reuse Economies: Working in Circles Mimics nature by recycling and reusing, thus reducing pollutants and waste. Mimics nature by recycling and reusing, thus reducing pollutants and waste. It is not sustainable for growing populations. It is not sustainable for growing populations.