CHAPTER 2 Science, Matter, Energy, and Systems

Core Case Study: A Story About a Forest Hubbard Brook Experimental Forest in New Hampshire Compared the loss of water and nutrients from an uncut forest (control site) with one that had been stripped (experimental site) Stripped site: 30-40% more runoff More dissolved nutrients More soil erosion

The Effects of Deforestation on the Loss of Water and Soil Nutrients Figure 2.1: This controlled field experiment measured the effects of deforestation on the loss of water and soil nutrients from a forest. V–notched dams were built at the bottoms of two forested valleys 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, and for the other valley, which acted as the experimental site (right). Then all the trees in the experimental valley were cut and, for 3 years, the flows of water and soil nutrients from both valleys were measured and compared. Fig. 2-1, p. 31

2-1 What Do Scientists Do? Concept 2-1 Scientists collect data and develop theories, models, and laws about how nature works.

Science Is a Search for Order in Nature (1) Identify a problem Find out what is known about the problem Ask a question to be investigated Gather data through experiments Propose a scientific hypothesis

Science Is a Search for Order in Nature (2) Make testable predictions Keep testing and making observations Accept or reject the hypothesis Scientific theory: well-tested and widely accepted hypothesis

The Scientific Process Figure 2.2: This diagram illustrates what scientists do. Scientists use this overall process for testing ideas about how the natural world works. However, they do not necessarily follow the order of steps shown here. For example, sometimes a scientist might start by coming up with a hypothesis to answer the initial question and then run experiments to test the hypothesis. Fig. 2-2, p. 33

Ask a question to be investigated Identify a problem Find out what is known about the problem (literature search) Ask a question to be investigated Perform an experiment to answer the question and collect data Scientific law Well-accepted pattern in data Analyze data (check for patterns) Propose a hypothesis to explain data Use hypothesis to make testable projections Figure 2.2: This diagram illustrates what scientists do. Scientists use this overall process for testing ideas about how the natural world works. However, they do not necessarily follow the order of steps shown here. For example, sometimes a scientist might start by coming up with a hypothesis to answer the initial question and then run experiments to test the hypothesis. Perform an experiment to test projections Accept hypothesis Revise hypothesis Make testable projections Test projections Scientific theory Well-tested and widely accepted hypothesis Fig. 2-2, p. 33

Testing a Hypothesis Figure 2.3: We can use the scientific process to understand and deal with an everyday problem. Fig. 2-3, p. 33

Nothing happens when I try to turn on my flashlight. Observation: Nothing happens when I try to turn on my flashlight. Question: Why didn’t the light come on? Hypothesis: Maybe the batteries are dead. Test hypothesis with an experiment: Put in new batteries and try to turn on the flashlight. Result: Flashlight still does not work. New hypothesis: Maybe the bulb is burned out. Figure 2.3: We can use the scientific process to understand and deal with an everyday problem. Experiment: Put in a new bulb. Result: Flashlight works. Conclusion: New hypothesis is verified. Fig. 2-3, p. 33

Characteristics of Science…and Scientists Curiosity Skepticism Reproducibility Peer review Openness to new ideas Critical thinking Creativity

Science Focus: Easter Island: Revisions to a Popular Environmental Story Some revisions to 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

Stone Statues on Easter Island Figure 2.A: These and many other massive stone figures once lined the coasts of Easter Island and are the remains of the technology created on the island by an ancient civilization of Polynesians. Some of these statues are taller than an average five-story building and can weigh as much as 89 metric tons (98 tons). Fig. 2-A, p. 35

Scientific Theories and Laws Are the Most Important Results of Science Scientific theory Widely tested Supported by extensive evidence Accepted by most scientists in a particular area Scientific law, law of nature

The Results of Science Can Be Tentative, Reliable, or Unreliable Tentative science, frontier science Reliable science Unreliable science

Science Has Some Limitations Particular hypotheses, theories, or laws have a high probability of being true while not being absolute Bias can be minimized by scientists Environmental phenomena involve interacting variables and complex interactions Statistical methods may be used to estimate very large or very small numbers Scientific process is limited to the natural world

Science Focus: Statistics and Probability Collect, organize, and interpret numerical data Probability The chance that something will happen or be valid Need large enough sample size

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 Has mass and takes up space Elements Unique properties Cannot be broken down chemically into other substances Compounds Two or more different elements bonded together in fixed proportions

Gold and Mercury Are Chemical Elements Figure 2.4: Gold (left) and mercury (right) are chemical elements; each has a unique set of properties and it cannot be broken down into simpler substances. Fig. 2-4a, p. 38

Chemical Elements Used in The Book Table 2-1, p. 38

Atoms, Ions, and Molecules Are the Building Blocks of Matter (1) Atomic theory All elements are made of atoms Subatomic particles Protons with positive charge and neutrons with no charge in nucleus Negatively charged electrons orbit the nucleus Atomic number Number of protons in nucleus Mass number Number of protons plus neutrons in nucleus

Model of a Carbon-12 Atom Figure 2.5: This is a greatly simplified model of a carbon-12 atom. It consists of a nucleus containing six protons, each with a positive electrical charge, and six neutrons with no electrical charge. Six negatively charged electrons are found outside its nucleus. We cannot determine the exact locations of the electrons. Instead, we can estimate the probability that they will be found at various locations outside the nucleus—sometimes called an electron probability cloud. This is somewhat like saying that there are six airplanes flying around inside a cloud. We do not know their exact location, but the cloud represents an area in which we can probably find them. Fig. 2-5, p. 39

6 protons 6 neutrons 6 electrons Figure 2.5: This is a greatly simplified model of a carbon-12 atom. It consists of a nucleus containing six protons, each with a positive electrical charge, and six neutrons with no electrical charge. Six negatively charged electrons are found outside its nucleus. We cannot determine the exact locations of the electrons. Instead, we can estimate the probability that they will be found at various locations outside the nucleus—sometimes called an electron probability cloud. This is somewhat like saying that there are six airplanes flying around inside a cloud. We do not know their exact location, but the cloud represents an area in which we can probably find them. 6 electrons Fig. 2-5, p. 39

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

Chemical Ions Used in This Book TABLE 2-2 Table 2-2, p. 40

pH Scale Figure 5 The pH scale, representing the concentration of hydrogen ions (H+) in one liter of solution is shown on the right-hand side. On the left side, are the approximate pH values for solutions of some common substances. A solution with a pH less than 7 is acidic, one with a pH of 7 is neutral, and one with a pH greater than 7 is basic. A change of 1 on the pH scale means a tenfold increase or decrease in H+ concentration. (Modified from Cecie Starr, Biology: Today and Tomorrow. Pacific Grove, CA: Brooks/Cole, © 2005) Supplement 5, Figure 4

Loss of NO3− from a Deforested Watershed Figure 2.6: This graph shows the loss of nitrate ions (NO3–) from a deforested watershed in the Hubbard Brook Experimental Forest (Figure 2-1, right). The average concentration of nitrate ions in runoff from the experimental deforested watershed was about 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) Fig. 2-6, p. 40

Nitrate (NO3–) concentration (milligrams per liter) 60 Nitrate (NO3–) concentration (milligrams per liter) 40 Disturbed (experimental) watershed Undisturbed (control) watershed 20 Figure 2.6: This graph shows the loss of nitrate ions (NO3–) from a deforested watershed in the Hubbard Brook Experimental Forest (Figure 2-1, right). The average concentration of nitrate ions in runoff from the experimental deforested watershed was about 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) 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 Year Fig. 2-6, p. 40

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

Compounds Used in This Book Table 2-3, p. 40

Organic Compounds Are the Chemicals of Life Hydrocarbons and chlorinated hydrocarbons Simple carbohydrates Macromolecules: complex organic molecules Complex carbohydrates Proteins Nucleic acids Lipids Inorganic compounds

Glucose Structure Figure 7 Straight-chain and ring structural formulas of glucose, a simple sugar that can be used to build long chains of complex carbohydrates such as starch and cellulose. Supplement 4, Fig. 4

Amino Acids and Proteins Figure 8 This model illustrates both the general structural formula of amino acids and a specific structural formula of one of the 20 different amino acid molecules that can be linked together in chains to form proteins that fold up into more complex shapes. Supplement 4, Fig. 8

Nucleotide Structure in DNA and RNA Figure 9 This diagram shows the generalized structures of the nucleotide molecules linked in various numbers and sequences to form large nucleic acid molecules such as various types of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). In DNA, the five-carbon sugar in each nucleotide is deoxyribose; in RNA it is ribose. The four basic nucleotides used to make various forms of DNA molecules differ in the types of nucleotide bases they contain—guanine (G), cytosine (C), adenine (A), and thymine (T). (Uracil, labeled U, occurs instead of thymine in RNA.) Supplement 4, Fig. 9

DNA Double Helix Structure and Bonding Figure 10 Portion of the double helix of a DNA molecule. The double helix is composed of two spiral (helical) strands of nucleotides. Each nucleotide contains a unit of phosphate (P), deoxyribose (S), and one of four nucleotide bases: guanine (G), cytosine (C), adenine (A), and thymine (T). The two strands are held together by hydrogen bonds formed between various pairs of the nucleotide bases. Guanine (G) bonds with cytosine (C), and adenine (A) with thymine (T). Supplement 4, Fig. 10

Fatty Acid Structure and Trigyceride Figure 11 The structural formula of fatty acid that is one form of lipid (left) is shown here. Fatty acids are converted into more complex fat molecules (center) that are stored in adipose cells (right). Supplement 4, Fig. 11

Matter Comes to Life through Genes, Chromosomes, and Cells Cells: fundamental units of life; all organisms are composed of one or more cells Genes Sequences of nucleotides within DNA Instructions for proteins Create inheritable traits Chromosomes: composed of many genes

Cells, Nuclei, Chromosomes, DNA, and Genes Figure 2.7: This diagram shows the relationships among cells, nuclei, chromosomes, DNA, and genes. Fig. 2-7, p. 42

Each human cell (except for red blood cells) contains a nucleus. A human body contains trillions of cells, each with an identical set of genes. Each human cell (except for red blood cells) contains a nucleus. Each cell nucleus has an identical set of chromosomes, which are found in pairs. A specific pair of chromosomes contains one chromosome from each parent. Figure 2.7: This diagram shows the relationships among cells, nuclei, chromosomes, DNA, and genes. Each chromosome contains a long DNA molecule in the form of a coiled double helix. Genes are segments of DNA on chromosomes that contain instructions to make proteins—the building blocks of life. Fig. 2-7, p. 42

Some Forms of Matter Are More Useful than Others High-quality matter Highly concentrated Near earth’s surface High potential as a resource Low-quality matter Not highly concentrated Deep underground or widely dispersed Low potential as a resource

Examples of Differences in Matter Quality Figure 2.8: These examples illustrate the 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. Fig. 2-8, p. 42

Solution of salt in water High Quality Low Quality Solid Gas Salt Solution of salt in water Coal Coal-fired power plant emissions Figure 2.8: These examples illustrate the 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. Gasoline Automobile emissions Aluminum can Aluminum ore Fig. 2-8, p. 42

2-3 What Happens When Matter Undergoes Change? Concept 2-3 Whenever 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 No change in chemical composition Chemical change, chemical reaction Change in chemical composition Reactants and products Nuclear change Natural radioactive decay Radioisotopes: unstable Nuclear fission Nuclear fusion

Types of Nuclear Changes Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Fig. 2-9, p. 43

Beta particle (electron) Radioactive decay Alpha particle (helium-4 nucleus) Radioactive isotope Gamma rays Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Beta particle (electron) Radioactive decay occurs when nuclei of unstable isotopes spontaneously emit fast-moving chunks of matter (alpha particles or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. A particular radioactive isotope may emit any one or a combination of the three items shown in the diagram. Fig. 2-9a, p. 43

Nuclear fission Uranium-235 Energy Fission fragment n n Neutron n n Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Radioactive isotope Radioactive decay occurs when nuclei of unstable isotopes spontaneously emit fast-moving chunks of matter (alpha particles or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. A particular radioactive isotope may emit any one or a combination of the three items shown in the diagram. Fig. 2-9b, p. 43

Nuclear fusion occurs when two isotopes of light elements, such Reaction conditions Fuel Products Proton Neutron Helium-4 nucleus Hydrogen-2 (deuterium nucleus) 100 million °C Energy Figure 2.9: There are three types of nuclear changes: natural radioactive decay (top), nuclear fission (middle), and nuclear fusion (bottom). Hydrogen-3 (tritium nucleus) Neutron Nuclear fusion occurs when two isotopes of light elements, such as hydrogen, are forced together at extremely high temperatures until they fuse to form a heavier nucleus and release a tremendous amount of energy. Fig. 2-9c, p. 43

We Cannot Create or Destroy Matter Law of conservation of matter Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed

2-4 What is Energy and What Happens When It Undergoes Change? 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 in a physical or chemical change, we end up with lower-quality or less usable energy than we started with (second law of thermodynamics).

Energy Comes in Many Forms (1) Kinetic energy Flowing water Wind Heat Transferred by radiation, conduction, or convection Electromagnetic radiation Potential energy Stored energy Can be changed into kinetic energy

Wind’s Kinetic Energy Moves This Turbine Figure 2.10: Kinetic energy, created by the gaseous molecules in a mass of moving air, turns the blades of this wind turbine. The turbine then converts this kinetic energy to electrical energy, which is another form of kinetic energy. Fig. 2-10, p. 44

The Electromagnetic Spectrum Figure 2.11: The electromagnetic spectrum consists of a range of electromagnetic waves, which differ in wavelength (the distance between successive peaks or troughs) and energy content. Fig. 2-11, p. 45

Shorter wavelengths and higher energy Visible light Shorter wavelengths and higher energy Infrared radiation Longer wavelengths and lower energy Gamma rays UV radiation X rays Microwaves TV, Radio waves 0.001 0.01 0.1 1 10 0.1 10 100 0.1 1 10 1 10 100 Wavelengths (not to scale) Figure 2.11: The electromagnetic spectrum consists of a range of electromagnetic waves, which differ in wavelength (the distance between successive peaks or troughs) and energy content. Nanometers Micrometers Centimeters Meters Fig. 2-11, p. 45

Potential Energy Figure 2.12: The water stored in this reservoir behind a dam in the U.S. state of Tennessee has potential energy, which becomes kinetic energy when the water flows through channels built into the dam where it spins a turbine and produces electricity—another form of kinetic energy. Fig. 2-12, p. 45

Energy Comes in Many Forms (2) Sun provides 99% of earth’s energy Warms earth to comfortable temperature Plant photosynthesis Winds Hydropower Biomass Fossil fuels: oil, coal, natural gas

Nuclear Energy to Electromagnetic Radiation Figure 2.13: Energy from the sun supports life and human economies. This energy is produced far away from the earth by nuclear fusion (Figure 2-9, bottom). In this process, nuclei of light elements such as hydrogen are forced together at extremely high temperatures until they fuse to form a heavier nucleus. This results in the release of a massive amount of energy that is radiated out through space. Fig. 2-13, p. 46

Fossil fuels Figure 2.14: Fossil fuels: Oil, coal, and natural gas (left, center, and right, respectively) supply most of the commercial energy that we use to supplement energy from the sun. Burning fossil fuels provides us with many benefits such as heat, electricity, air conditioning, manufacturing, and mobility. But when we burn these fuels, we automatically add carbon dioxide and various other pollutants to the atmosphere. Fig. 2-14a, p. 46

Some Types of Energy Are More Useful Than Others High-quality energy High capacity to do work Concentrated High-temperature heat Strong winds Fossil fuels Low-quality energy Low capacity to do work Dispersed

Ocean Heat Is Low-Quality Energy Figure 2.15: A huge amount of the sun’s energy is stored as heat in the world’s oceans. But the temperature of this widely dispersed energy is so low that we cannot use it to heat matter to a high temperature. Thus, the ocean’s stored heat is low-quality energy. Question: Why is direct solar energy a higher-quality form of energy than the ocean’s heat is? Fig. 2-15, p. 47

Energy Changes Are Governed by Two Scientific Laws First Law of Thermodynamics Law of conservation of energy Energy is neither created nor destroyed in physical and chemical changes Second Law of Thermodynamics Energy always goes from a more useful to a less useful form when it changes from one form to another Light bulbs and combustion engines are very inefficient: produce wasted heat

Energy-Wasting Technologies Figure 2.16: Two widely used technologies waste enormous amounts of energy. In an incandescent lightbulb (right), about 95% of the electrical energy flowing into it becomes heat; just 5% becomes light. By comparison, in a compact fluorescent bulb (left) with the same brightness, about 20% of the energy input becomes light. In the internal combustion engine (right photo) found in most motor vehicles, about 87% of the chemical energy provided in its gasoline fuel flows into the environment as low-quality heat. (Data from U.S. Department of Energy and Amory Lovins; see his Guest Essay at CengageNOW.) Fig. 2-16a, p. 48

2-5 What Are Systems and How Do They Respond to Change? Concept 2-5 Systems have inputs, flows, and outputs of matter and energy, and feedback can affect their behavior.

Systems Have Inputs, Flows, and Outputs Set of components that interact in a regular way Human body, earth, the economy Inputs from the environment Flows, throughputs of matter and energy Outputs to the environment

Inputs, Throughput, and Outputs of an Economic System Figure 2.17: This diagram illustrates a greatly simplified model of a system. Most systems depend on inputs of matter and energy resources, and outputs of wastes, pollutants, and heat to the environment. A system can become unsustainable if the throughputs of matter and energy resources exceed the abilities of the system’s environment to provide the required resource inputs and to absorb or dilute the resulting wastes, pollutants, and heat. Fig. 2-17, p. 48

Inputs (from environment) Outputs (to environment) Throughputs Energy resources Work or products Matter resources System processes Waste and pollution Information Heat Figure 2.17: This diagram illustrates a greatly simplified model of a system. Most systems depend on inputs of matter and energy resources, and outputs of wastes, pollutants, and heat to the environment. A system can become unsustainable if the throughputs of matter and energy resources exceed the abilities of the system’s environment to provide the required resource inputs and to absorb or dilute the resulting wastes, pollutants, and heat. Fig. 2-17, p. 48

Systems Respond to Change through Feedback Loops Positive feedback loop Causes system to change further in the same direction Can cause major environmental problems Negative, or corrective, feedback loop Causes system to change in opposite direction

Positive Feedback Loop Figure 2.18: This diagram represents a positive feedback loop. Decreasing vegetation in a valley causes increasing erosion and nutrient losses that in turn cause more vegetation to die, resulting in more erosion and nutrient losses. Question: Can you think of another positive feedback loop in nature? Fig. 2-18, p. 49

Decreasing vegetation... ... which causes more vegetation to die. ... leads to erosion and nutrient loss... Figure 2.18: This diagram represents a positive feedback loop. Decreasing vegetation in a valley causes increasing erosion and nutrient losses that in turn cause more vegetation to die, resulting in more erosion and nutrient losses. Question: Can you think of another positive feedback loop in nature? Fig. 2-18, p. 49

Negative Feedback Loop Figure 2.19: This diagram illustrates a negative 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 to turn the furnace on until the desired temperature is reached again. Fig. 2-19, p. 50

Temperature reaches desired setting and furnace goes off House warms Temperature reaches desired setting and furnace goes off Furnace on Furnace off Figure 2.19: This diagram illustrates a negative 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 to turn the furnace on until the desired temperature is reached again. House cools Temperature drops below desired setting and furnace goes on Fig. 2-19, p. 50

Time Delays Can Allow a System to Reach a Tipping Point Time delays vary Between the input of a feedback stimulus and the response to it Tipping point, threshold level Causes a shift in the behavior of a system Melting of polar ice Population growth

System Effects Can Be Amplified through Synergy Synergistic interaction, synergy Two or more processes combine in such a way that combined effect is greater than the two separate effects Helpful Studying with a partner Harmful E.g., Smoking and inhaling asbestos particles

The Usefulness of Models for Studying Systems Identify major components of systems and interactions within system, and then write equations Use computer to describe behavior, based on the equations Compare projected behavior with known behavior Can use a good model to answer “if-then“ questions

Three Big Ideas There is no away. You cannot get something for nothing. You cannot break even.