Science, Matter, Energy, and Systems

Science, Matter, Energy, and Systems Chapter 2

Figure 2.1Controlled field experiment to measure the effects of deforestation on the loss of water and soil nutrients from a forest. V–notched dams were built into the impenetrable bedrock at the bottoms of several forested valleys (left) so that all water and nutrients flowing from each valley could be collected and measured for volume and mineral content. These measurements were recorded for the forested valley (left), which acted as the control site. Then all the trees in another valley (the experimental site) were cut (right) and the flows of water and soil nutrients from this experimental valley were measured for 3 years.

Core Case Study: Carrying Out a Controlled Scientific Experiment • F. Herbert Bormann, Gene Likens, et al.: Hubbard Brook Experimental Forest in NH (U.S.) • Compared the loss of water and nutrients from an uncut forest (control site) with one that had been stripped (experimental site) • Deforested area: 30-40% increase in water flowing out of forest, eroded soil, and lost 6 to 8 times more nutrients

2-1 What Is Science? • Concept 2-1 Scientists collect data and develop theories, models, and laws about how nature works. • Science – endeavor to discover how nature works and to use that knowledge to make predictions about what is likely to happen in nature. • Based on the assumption that events in the natural world follow orderly cause-and-effect patterns that can be understood through careful observation, measurements, experimentation, and modeling.

Science Is a Search for Order in Nature (1) Figure 2.2 What scientists do. The essence of science is this process for testing ideas about how nature works. Scientists do not necessarily follow the exact order of steps shown here. For example, sometimes a scientist might start by formulating a hypothesis to answer the initial question and then run experiments to test the hypothesis.

Science Is a Search for Order in Nature (2) • Some terms • Data – information needed to answer a question; collected with senses or extensions of the senses. • Experiments – procedures carried out under controlled conditions to gather information and test ideas. • Scientific hypothesis – a possible and testable explanation of what is observed in nature or in the results of their experiments. • Model – an approximate representation or simulation of a system being studied. • Scientific theory – well-tested hypothesis or group of hypotheses; and explanation that has broad predictive power. • Peer review

Science Is a Search for Order in Nature (3) • Important features of the scientific process • Curiosity • Skepticism • Peer review • Reproducibility • Openness to new ideas

Science Focus: Easter Island: Revisions to a Popular Environmental Story • Original thoughts: • Polynesians arrived 2,900 years ago • Populations up to 15,000 • Only 100 native islanders left by 1870’s because of overuse of trees and supplies • Some revisions in a popular environmental story • Polynesians arrived about 800 years ago • Population may have reached 3000 • Used trees in an unsustainable manner, but rats may have multiplied and eaten the seeds of the trees

Scientists Use Reasoning, Imagination, and Creativity to Learn How Nature Works • Important scientific tools • Inductive reasoning – uses specific observations and measurements to arrive at a general conclusion or hypothesis. • Deductive reasoning – uses logic to arrive at a specific conclusion based on a generalization or premise. • Scientists also use • Intuition • Imagination • Creativity

Scientific Theories and Laws Are the Most Important Results of Science • Scientific theory – and explanation for natural phenomena. • Widely tested • Supported by extensive evidence • Accepted by most scientists in a particular area • Scientific law, or law of nature – a well-tested and widely accepted description of what we find happening over and over again in the same way in nature. • Paradigm shift – when new discoveries and new ideas overthrow a well-accepted theory; occurs when majority of scientist in the related fields a new paradigm.

Science Focus: The Scientific Consensus over Global Warming (1) • Greenhouse effect, one of the most widely accepted theories in atmospheric science. • Since 1980, many climatologist have been focused on these questions: • How much has the earth’s atmosphere warmed during the last 50 years? • How much of this warming is due to human activity? • How much is the atmosphere likely to warm in the future and will this affect climate? • The UN and the World Meteorological Organization established the IPCC • Studies how climate systems work, document past climate changes, and project future changes.

Science Focus: The Scientific Consensus over Global Warming (2) • The 4th IPCC report, 2007 • Very likely (90-99% probability) that the troposphere is getting warmer. • Very likely (90-99% probability) that human activities have been the cause. • Very likely (90-99% probability) that temperatures will increase by at least 3 oC between 2005 and 2100. • Report is considered reliable science. • Some individual scientist disagree. • Media coverage causes bias by providing balanced coverage.

The Results of Science Can Be Tentative, Reliable, or Unreliable • Tentative science, or frontier science – preliminary results that have not been widely tested and accepted by peer review. • Reliable science – consists of data, hypotheses, theories and laws that are widely accepted by scientists who are considered experts in the field; based on a self-correcting process. • Unreliable science – hypotheses and results that are presented as reliable without having undergone the rigors of peer review, or that have been discarded as a result of peer review. • Questions to ask to help evaluate scientific claims, p. 34

The Results of Science Can Be Tentative, Reliable, or Unreliable • Particular hypotheses, theories, or laws have a high probability of being true while not being absolute. • Can’t “prove” anything; there is always some degree of uncertainty in measurements, observations and models. • Bias can be minimized by scientists. • Statistical methods may be used to estimate very large or very small numbers. • Just because they are estimates, the numbers should not be dismissed. The estimates can indicate important trends. • Environmental phenomena involve interacting variables and complex interactions. • Scientific process is limited to the natural world.

Science Focus: Statistics and Probability • Statistics – mathematical tools used to collect, organize, and interpret numerical data. • Probability - the chance that something will happen or be valid. • Critical Thinking: What does it mean when an international body of the world’s climate experts says that there is a 90-99% chance (probability of 0.90-0.99) that human activities, led by emissions of carbon dioxide from burning fossil fuels, have been the main cause of the observed atmospheric warming during the past 50 years? Why would the probability never be 100%?

2-2 What Is Matter? • Concept 2-2 Matter consists of elements and compounds, which are in turn made up of atoms, ions, or molecules.

Matter Consists of Elements and Compounds • Matter • Has mass and takes up space • The stuff that makes up life and its environments • Elements • Unique properties • Cannot be broken down chemically into other substances • Four elements⎯O, C, H, and N⎯make up about 96% of the mass of most organisms. • Compounds • Two or more different elements bonded together in fixed proportions

Elements Important to the Study of Environmental Science

Atoms, Ions, and Molecules Are the Building Blocks of Matter (1) • Atom – basic building block of matter; smallest unit of matter into which an element can be divided and still retain its chemical properties. • Atomic theory • Subatomic particles • Protons (p) with positive charge and neutrons (0) with no charge in nucleus • Negatively charged electrons (e) orbit the nucleus • Mass number • Protons plus neutrons • Isotopes

Model of a Carbon-12 Atom

Atoms, Ions, and Molecules Are the Building Blocks of Matter (2) • Ions • Gain or lose electrons • Form ionic compounds • pH • Measure of acidity • H+ and OH-

Ions Important to the Study of Environmental Science

Figure 2.4Loss of nitrate ions (NO3−) from a deforested watershed in the Hubbard Brook Experimental Forest in New Hampshire (Figure 2-1, right). The average concentration of nitrate ions in runoff from the deforested experimental watershed was 60 times greater than in a nearby unlogged watershed used as a control (Figure 2-1, left). (Data from F. H. Bormann and Gene Likens)

Atoms, Ions, and Molecules Are the Building Blocks of Matter (3) • Molecule • Two or more atoms of the same or different elements held together by chemical bonds • Chemical formula

Compounds Important to the Study of Environmental Science

Organic Compounds are the Chemicals of Life • Inorganic compounds • Organic compounds • Hydrocarbons (compounds of C and H) like methane • Chlorinated hydrocarbons (compounds of C, H and Cl) like DDT (C14H9Cl5) • Simple carbohydrates like glucose • Macromolecules: complex organic molecules; polymers made of subunit monomers. • Complex carbohydrates (many simple sugars) • Proteins (amino acids) • Nucleic acids (nucleotides) • Lipids (fats, oils and waxes)

Matter Comes to Life through Genes, Chromosomes, and Cells • The bridge between living and nonliving lies somewhere between macromolecules and cells. • Cells – fundamental units of life • Genes – sequences of nucleotides within the DNA • Chromosomes – composed of many genes

Matter Occurs in Various Physical Forms • Solid • Liquid • Gas

Some Forms of Matter Are More Useful than Others • Matter quality – measure of how useful a form of matter is to humans as a resource based on availability and concentration. • High-quality matter • Low-quality matter Figure 2.6 Examples of differences in matter quality. High-quality matter (left column) is fairly easy to extract and is highly concentrated; low-quality matter (right column) is not highly concentrated and is more difficult to extract than high-quality matter.

2-3 How Can Matter Change? • Concept 2-3 When matter undergoes a physical or chemical change, no atoms are created or destroyed (the law of conservation of matter).

Matter Undergoes Physical, Chemical, and Nuclear Changes • Physical change – chemical composition does not change. • Chemical change, chemical reaction • Nuclear change • Natural radioactive decay • Radioisotopes: unstable • Nuclear fission • Chain reaction – when multiple fissions of a certain mass occurs; releases enormous amounts of energy. • Nuclear fusion

Figure 2-7 a

Figure 2-7 b

Figure 2-7 c

Modeling Radioactive Decay

We Cannot Create or Destroy Matter • Law of conservation of matter • What is meant by matter consumption? • Matter is converted from one form to another. • No such thing as throwing something away

2-4 What is Energy and How Can It Be Changed? • Concept 2-4A When energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed (first law of thermodynamics). • Concept 2-4B Whenever energy is changed from one form to another, we end up with lower- quality or less usable energy than we started with (second law of thermodynamics).

Energy Comes in Many Forms • What is energy? • Work = force x distance • Kinetic energy • Heat (textbook defines incorrectly.) • Transferred by radiation, conduction, or convection • Electromagnetic radiation • Potential energy • Stored energy • Can be changed into kinetic energy

Figure 2.8Solar capital: the spectrum of electromagnetic radiation released by the sun consists mostly of visible light.

Some Types of Energy Are More Useful Than Others • Energy quality – a measure of an energy source’s capacity to do useful work. • High-quality energy – concentrated w/ high capacity to do work. • Examples: fossil fuels, high heat, strong wind, nuclear fission. • Low-quality energy – dispersed and little capacity to do work. • Examples: thermal energy in atmosphere and oceans.

Energy Changes Are Governed by Two Scientific Laws (1) • Thermodynamics is the study of energy transformations. • First Law of Thermodynamics • Energy input always equals energy output

Energy Changes Are Governed by Two Scientific Laws (2) • Second Law of Thermodynamics • Energy always goes from a more useful to a less useful form when it changes from one form to another. • Energy quality is lost. • Examples: 94% of energy in gas is degraded to heat, only 6% gets you to places. Only 5% of electrical energy generates light in an incandescent bulb. Heat bulb? • Energy efficiency, or energy productivity • This is a measure of how much useful work is done by a particular input of energy into a system. • 16% of energy in the US actually does useful work. • 41% is unavoidable. • 43% is unnecessarily wasted. • Lesson: Cheapest and quickest way to get more energy is to stop wasting almost half the energy we use.

Figure 2.9The 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.

2-5 What Are Systems and How Do They Respond to Change? • Concept 2-5A Systems have inputs, flows, and outputs of matter and energy, and their behavior can be affected by feedback. • Concept 2-5B Life, human systems, and the earth’s life support systems must conform to the law of conservation of matter and the two laws of thermodynamics.

Systems Have Inputs, Flows, and Outputs • System – a set of components that function and interact in some regular way. • Most systems have the following key components: • Inputs from the environment • Flows, or throughputs • Outputs to the environment

Figure 2.10Inputs, throughput, and outputs of an economic system. Such systems depend on inputs of matter and energy resources and outputs of waste and heat to the environment. Such a system can become unsustainable if the throughput of matter and energy resources exceeds the ability of the earth’s natural capital to provide the required resource inputs or the ability of the environment to assimilate or dilute the resulting heat, pollution, and environmental degradation.

Systems Respond to Change through Feedback Loops • Feedback – any process that increases (positive feedback) or decreases (negative feedback) a change to a systems. • Feedback loop – occurs when an output of matter, energy or information is fed back into the system as an input and leads to changes in the system. • Positive feedback loop • Negative, or corrective, feedback loop

Figure 2.11Positive feedback loop. Decreasing vegetation in a valley causes increasing erosion and nutrient losses, which in turn causes more vegetation to die, which allows for more erosion and nutrient losses. The system receives feedback that continues the process of deforestation.

Figure 2.12Negative feedback loop. When a house being heated by a furnace gets to a certain temperature, its thermostat is set to turn off the furnace, and the house begins to cool instead of continuing to get warmer. When the house temperature drops below the set point, this information is fed back, and the furnace is turned on and runs until the desired temperature is reached. The system receives feedback that reverses the process of heating or cooling.

Time Delays Can Allow a System to Reach a Tipping Point • Complex system often have time delays between the input of a feedback stimulus and the response to it. • Time delays vary depending on the system. • Time delays can allow and environmental problem to build up to a tipping point, or threshold level. • Causes a shift in the behavior of a system • Examples: clearing vegetation, population growth, leaks from toxic waste dumps, global climate change, degradation of forests from long-term exposure to pollutants.

Science, Matter, Energy, and Systems