Science, Systems, Matter, and Energy Chapter 2 Science, Systems, Matter, and Energy

THE NATURE OF SCIENCE What do scientists do? Collect data. Form hypotheses. Develop theories, models and laws about how nature works. Figure 2-2

Scientific Theories and Laws: The Most Important Results of Science Scientific Theory Widely tested and accepted hypothesis. Scientific Law What we find happening over and over again in nature. Figure 2-3

Testing Hypotheses Scientists test hypotheses using controlled experiments and constructing mathematical models. Variables or factors influence natural processes Single-variable experiments involve a control and an experimental group. Most environmental phenomena are multivariable and are hard to control in an experiment. Models are used to analyze interactions of variables.

Scientific Reasoning and Creativity Inductive reasoning Involves using specific observations and measurements to arrive at a general conclusion or hypothesis. Bottom-up reasoning going from specific to general. Deductive reasoning Uses logic to arrive at a specific conclusion. Top-down approach that goes from general to specific.

Frontier Science, Sound Science, and Junk Science Frontier science has not been widely tested (starting point of peer-review). Sound science consists of data, theories and laws that are widely accepted by experts. Junk science is presented as sound science without going through the rigors of peer-review.

Limitations of Environmental Science Inadequate data and scientific understanding can limit and make some results controversial. Scientific testing is based on disproving rather than proving a hypothesis. Based on statistical probabilities.

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 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) 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. 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.

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 oxide, 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.

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

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. 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

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 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

Source of Energy Energy Tasks Relative Energy Quality (usefulness) Electricity Very high temperature heat (greater than 2,500°C) Nuclear fission (uranium) Nuclear fusion (deuterium) Concentrated sunlight High-velocity wind Very high-temperature heat (greater than 2,500°C) for industrial processes and producing electricity to run electrical devices (lights, motors) High-temperature heat (1,000–2,500°C) Hydrogen gas Natural gas Gasoline Coal Food Mechanical motion to move vehicles and other things) High-temperature heat (1,000–2,500°C) for industrial processes and producing electricity Normal sunlight Moderate-velocity wind High-velocity water flow Concentrated geothermal energy Moderate-temperature heat (100–1,000°C) Wood and crop wastes Moderate-temperature heat (100–1,000°C) for industrial processes, cooking, producing steam, electricity, and hot water Figure 2.13 Natural capital: categories of the qualities of different sources of energy. High-quality energy is concentrated and has great ability to perform useful work. Low-quality energy is dispersed and has little ability to do useful work. To avoid unnecessary energy waste, you should match the quality of an energy source with the quality of energy needed to perform a task. Dispersed geothermal energy Low-temperature heat (100°C or lower) Low-temperature heat (100°C or less) for space heating Fig. 2-13, p. 44

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. 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. Energy efficiency is a measure of how much useful work is accomplished before it changes to its next form.

Mechanical energy (moving, thinking, living) Chemical energy (photosynthesis) Chemical energy (food) Solar energy Waste Heat Waste Heat Waste Heat Waste Heat Figure 2.14 The second law of thermodynamics in action in living systems. Each time energy changes from one form to another, some of the initial input of high-quality energy is degraded, usually to low-quality heat that is dispersed into the environment. Fig. 2-14, p. 45

SUSTAINABILITY AND MATTER AND ENERGY LAWS Unsustainable High-Throughput Economies: Working in Straight Lines Converts resources to goods in a manner that promotes waste and pollution. Figure 2-15

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. It is not sustainable for growing populations.

Sustainable low-waste economy Matter Feedback Energy Feedback Inputs (from environment) System Throughputs Outputs (into environment) Energy conservation Low-quality Energy (heat) Energy Sustainable low-waste economy Waste and pollution Waste and pollution Pollution control Matter Recycle and reuse Figure 2.16 Solutions: lessons from nature. A low-throughput economy, based on energy flow and matter recycling, works with nature to reduce the throughput of matter and energy resources (items shown in green). This is done by (1) reusing and recycling most nonrenewable matter resources, (2) using renewable resources no faster than they are replenished, (3) using matter and energy resources efficiently, (4) reducing unnecessary consumption, (5) emphasizing pollution prevention and waste reduction, and (6) controlling population growth. Matter Feedback Energy Feedback Fig. 2-16, p. 47