Excerpts from Living in the Environment, G. Tyler Miller, Chapter 3, 8th Ed.
Science is an attempt to discover order in nature and then use that knowledge to make predictions or projections about what will happen in nature. In this search for order scientists try to answer two basic questions: (1) What events happen in nature over and over with the same results? and (2) How or why do things happen this way?
WHAT DO SCIENTISTS DO?
Scientists collect scientific data, or facts, by making observations and taking measurements, but this is not the main purpose of science. As French scientist Henri Poincare put it, “Science is built up of facts, but a collection of facts is no more science than a heap of stones is a house.”
Scientists try to describe what is happening by organizing data into a generalization or scientific law. Thus scientific data are stepping stones to a scientific law, a description of the orderly behavior observed in nature ‑ a summary of what we find happening in nature over and over in the same way. For example, after making thousands of measurements involving changes in matter, chemists concluded that in any physical change (such as converting liquid water to water vapor) or any chemical change (such as burning coal) no matter is created or destroyed. This summary of what we always observe in nature is called the law of conservation of matter, as discussed in more detail later in this chapter.
Scientists then try to explain how or why things happen the way a scientific law describes. For example, why does the law of conservation of matter work? To answer such questions, investigators develop a scientific hypothesis, an educated guess that explains a scientific law or certain scientific facts. More than 2,400 years ago Greek philosophers proposed that all matter is composed of tiny particles called atoms, but they had no experimental evidence to back up their atomic hypothesis.
If many experiments by different scientists support the hypothesis, it becomes a scientific theory – a well-tested and widely accepted scientific hypothesis. During the last two centuries scientists have done experiments that elevated the atomic hypothesis to the atomic theory of matter. This theory, in turn, explains the law of conservation of matter with the idea that in any physical or chemical change no atoms can be created or destroyed.
ARE SCIENTIFIC THEORIES AND LAWS TRUE?
A favorite debating and advertising trick is to claim that something “has not been scientifically proved.” But scientists can’t establish absolute proof or truth. They are concerned only with how useful a theory or a law is in describing, explaining, and predicting what happens in nature.
Science can disprove things, but it can never prove anything. Scientific laws and theories are based on statistical probabilities, not on certainties. Science gives us information in the following form: If we do so‑and‑ (say, add certain chemicals to the atmosphere at particular rates), there is a certain chance that we will cause various effects (such as change the climate or deplete ozone in the stratosphere). Scientific hypotheses and theories are also dynamic ideas that are constantly tested and challenged. Often they may be modified, or even discarded, because of new data or more useful explanations of current data.
Science advances by debate, argument, speculation, and controversy. Disputes among scientists are what the media usually report. Such disagreements make juicier stories, but what’s really important is the consensus among scientists about various scientific ideas and issues. This substantial agreement–the real knowledge of science‑-rarely gets reported, giving the public a false idea of the nature of science and of scientific knowledge.
The ways scientists gather data and formulate and test scientific hypotheses, laws, and theories are called scientific methods. A scientific method is a set of questions with no particular rules for answering them. The questions a scientist attempts to answer are these:
- What questions about nature should I try to answer?
- What relevant facts are already known, and what new data should I collect?
- How should I collect these data?
- How can I organize and analyze the data I have collected to develop a pattern of order or scientific law?
- How can I come up with a hypothesis to explain the law and use it to predict some new facts?
- Is this the simplest and only reasonable hypothesis?
- What new experiments should I run to test the hypothesis (and modify it if necessary) so it can become a scientific theory?
New discoveries happen in many ways. Some follow a data ‑ law ‑ hypothesis ‑ theory sequence. Other times scientists simply follow a hunch or a bias and then do experiments to test it. Some discoveries occur when an experiment gives totally unexpected results and the scientist insists on finding out what happened. So, in reality, there are many methods of science rather than one scientific method.
Trying to discover order in nature requires logical reasoning, but it also requires imagination and intuition. As Albert Einstein once said, “Imagination is more important than knowledge, and there is no completely logical way to a new scientific idea.”
Intuition and creativity are as important in science as they are in poetry, art, music, and other great adventures of the human spirit that awaken us to the wonder, mystery, and beauty of the universe, the earth, and life.
IS SCIENCE ALWAYS OBJECTIVE? Science is often held up as being value‑free and neutral, with scientists not allowing their personal beliefs and biases or outside pressures to influence their work. But scientists are ordinary human beings, with conscious and unconscious biases, values, opinions, and financial and other needs that can influence what questions they ask of nature, how they design experiments, and how they interpret the results. Open publishing of results and mutual criticism among scientists help correct for biases more than in other professions, but they do not remove them.
Doing most science today is so expensive that few scientists can finance their own research. This explains why about half the world’s scientists work on military related research and development and more than a third work directly or indirectly for large corporations. Much of this work is not published and thus is not open to evaluation and correction. If these scientists challenge or decline to publicly support the positions of organizations they depend on for a living, they may face unemployment or loss of research grants.
WHAT IS TECHNOLOGY? Technology is the creation of new products and processes that are supposed to improve our chances for survival, our comfort level, and our quality of life. In many cases technology develops from known scientific laws and theories. Scientists invented the laser, for example, by applying knowledge about the internal structure of atoms. Applied scientific knowledge about chemistry has given us nylon, pesticides, laundry detergents, pollution control devices, and countless other products.
Some technologies arose long before anyone understood the underlying scientific principles. For example, aspirin, extracted from the bark of a willow tree, relieved pain and fever long before anyone found out how it did so. Similarly, photography was invented by people who had no inkling of its chemistry. And farmers crossbred new strains of livestock and crops long before biologists understood the principles of genetics.
Science and technology differ in the way the information and ideas they produce are shared. Many of the results of scientific research are published and passed around freely to be tested, challenged, verified, or modified, a process that strengthens the validity of scientific knowledge and helps expose cheaters. In contrast, technological discoveries are often kept secret until the new process or product is patented.
ENVIRONMENTAL SCIENCE: HOLISTIC SCIENCE
For the past 250 years scientists have studied nature mostly by examining successively lower levels of organization of matter. This approach is called reductionism. It is based on the belief that if we can understand subatomic particles, atoms, and molecules, then we can work our way up the ladder of organizational levels of matter to understand organisms (distinct forms of life classified as species), populations (individuals of the same species living in a particular place or habitat), communities (populations of all species living in a particular habitat), ecosystems (a community of different species interacting with one another and their nonliving environment), the ecosphere (the collection of all of Earth’s ecosystems), and eventually the universe.
The reductionist approach has taught us much about nature, but it provides an incomplete picture. Each higher level of organization of matter has properties that cannot be predicted or understood merely by understanding the lower levels that make up its structure. Even if you learn all there is to know about a particular tree, for example, you will know only a small part of how a forest works, and even less about the interactions between the forest and other living and nonliving parts of the environment.
The science of ecology has shown the need for combining reductionism with holism (sometimes spelled “wholism”) – an attempt to describe all properties of a level of organization, not merely those based on the lower levels of organization that make up its underlying structure. This approach also attempts to understand and describe how the various levels of organization interact with one another and with their constantly changing environments. This challenging and incredibly complex task requires research and cooperation among disciplines. Unfortunately such research is rare, because most of the jobs and grants in scientific disciplines reward those who do specialized research in their disciplines.
Environmental science is the study of how we and other species interact with one another and with the nonliving environment of matter and energy. It is a holistic physical and social science that uses and integrates knowledge from physics, chemistry, biology (especially ecology), geology, geography, resource technology and engineering, resource conservation and management, demography (the study of population dynamics), economics, politics, and ethics. In other words, it is a study of how everything works and interacts – a study of connections in the common home of all living things.
SCIENCE, TECHNOLOGY, AND THE FUTURE Advances in science and technology have clearly improved the lives of many people. This progress, however, has also produced unforeseen effects, such as pollution, that diminish the quality of our lives and threaten some of Earth’s life support systems.
Our challenge as a society is to learn how to use scientific knowledge and technology to sustain the earth for humans and other species, and to improve the quality of life for all people-not to plunder the planet for short-term economic gain. This means that scientists and technologists need to consider the possible short- and long-range implications of their research, air these thoughts, and engage the public and decision makers in an ongoing debate about the ends that science should serve. To help achieve this goal, the education of all scientists and engineers should include courses on holistic and integrative thinking and on Earth ethics.
It’s also important for non-scientists to have a basic knowledge of how nature works, because most decisions about how to use science and technology are made by non-scientists, usually with advice from scientists. Decision makers in business and government must have enough general knowledge of science and technology to ask tough questions of scientists and engineers, evaluate the answers, and make difficult decisions, usually with incomplete information.
Matter: Forms, Structure, and Quality
NATURE’S BUILDING BLOCKS: CHEMICAL AND PHYSICAL FORMS OF MATTER
Matter is anything that has mass (the amount of material in an object) and takes up space. It includes the solids, liquids, and gases around you and within your body. Matter is found in three chemical forms: elements (the distinctive building blocks of matter that make up every material substance), compounds (two or more different elements held together in fixed proportions by attractive forces called chemical bonds), and mixtures (combinations of elements, compounds, or both).
All matter is built from the 109 known chemical elements. Ninety‑two of them occur naturally, and the other 17 have been synthesized in laboratories. Each of these elements has a size, an internal structure, and other properties that make it unique, just as each of the 26 letters in the English alphabet is different from all the others. To simplify things, chemists represent each element by a one‑ or two‑letter symbol, for example, hydrogen (H), carbon (C), oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), chlorine (CI), fluorine (F), bromine (Br), sodium (Na), calcium (Ca), and uranium (U).
If you had a super microscope to look at elements and compounds, you would discover that they are made up of three types of building blocks: atoms (the smallest unit of matter that is unique to a particular element), ions (electrically charged atoms), and molecules (combinations of atoms of the same or different elements held together by chemical bonds). Since ions and molecules are formed from atoms, atoms are the ultimate building blocks for all matter.
Some elements are found in nature as molecules. Examples are nitrogen and oxygen, which make up about 99% of the volume of the air we breathe. Two atoms of nitrogen (N) combine to form a nitrogen gas molecule with the shorthand formula N2 (read as “N- two”). The subscript after the symbol of the element gives the number of atoms of that element in a molecule. Similarly most of the oxygen in the atmosphere exists as O2 (read as “O‑two”) molecules. A small amount of oxygen, found mostly in the second layer of the atmosphere (stratosphere), exists as 03 (read as “O-three”) molecules; this type of oxygen is called ozone.
Elements can combine to form an almost limitless number of compounds, just as the letters of our alphabet have been combined to form almost a million English words. So far, chemists have identified more than 10 million compounds.
Matter is also found in three physical states: solid, liquid, and gas. Water, for example, exists as ice, liquid water, and water vapor depending on its temperature and pressure. The differences among the three physical states of a sample of matter are in the relative orderliness of its atoms, ions, or molecules, with solids having the most orderly arrangement and gases the least orderly.
ATOMS AND IONS If you increased the magnification of your super microscope, you would find that each different type of atom is composed of a certain number of subatomic particles. The main building blocks of an atom are positively charged protons (represented by the symbol p), uncharged neutrons (n), and negatively charged electrons (e). Many other subatomic particles have been identified in recent years, but they need not concern us here.
Each atom consists of a relatively small center, or nucleus, containing protons and neutrons, and one or more electrons in rapid motion somewhere around the nucleus. We can describe electrons only in terms of the probability that they might be at various locations outside the nucleus.
The distinguishing feature of an atom of any given element is the number of protons in its nucleus, called its atomic number. The simplest element, hydrogen (H), has only 1 proton in its nucleus, so its atomic number is 1. Carbon (C), with 6 protons, has an atomic number of 6; uranium (U), a much larger atom, has 92 protons and an atomic number of 92.
Atoms normally have the same number of positively charged protons and negatively charged electrons and thus do not carry an electrical charge. For example, an uncharged atom of hydrogen has one positively charged proton in its nucleus and one negatively charged electron outside its nucleus. Similarly, each atom of uranium has 92 protons in its nucleus and 92 electrons outside.
Protons and neutrons have essentially the same mass and are assigned a relative mass of 1. Each electron is assigned a relative mass of 0 because its mass is almost negligible compared with the mass of a proton or a neutron. This means that the approximate relative mass of an atom is determined by the number of neutrons plus the number of protons in its nucleus. This number is called its mass number. An atom of hydrogen with 1 proton and no neutrons has a mass number of 1, and an atom of uranium with 92 protons and 143 neutrons has a mass number of 235.
Although all atoms of an element have the same number of protons in their nuclei, they may have different numbers of uncharged neutrons in their nuclei and thus different mass numbers. These different forms of an element with the same atomic number but a different mass number are called isotopes of that element. Isotopes are identified by attaching their mass numbers to the name or symbol of the element. Hydrogen, for example, has three isotopes: hydrogen-1, or H-1; hydrogen-2, or H-2 (common name, deuterium); and hydrogen-3, or H-3 (common name, tritium). A natural sample of an element contains a mixture of its isotopes in a fixed proportion or percent abundance by weight (Figure 3-3).
Atoms of some elements can lose or gain one or more electrons to form ions: atoms or groups of atoms with one or more net positive (+) or negative (-) electrical charges. For example, an atom of sodium (Na) can lose one of its electrons and become a sodium ion with a positive charge of one (Na+). An atom of chlorine (CI) can gain an electron and become a chlorine ion with a negative charge of one (CI—). The number of positive or negative charges on an ion is shown as a superscript after the symbol for an atom or a group of atoms. Examples of other positive ions are calcium ions (Ca2+) and ammonium ions (NH4+). Other common negative ions are nitrate ions (N03–), sulfate ions (S042-), and phosphate ions (PO43-).
COMPOUNDS Most matter exists as compounds–previously defined as combinations of different atoms or ions, of two or more different elements held together by chemical bonds. Chemists use a shorthand chemical formula to show the number of atoms (or ions) of each type found in the basic structural unit of a compound. The formula contains the symbols for each of the elements present and uses subscripts to show the number of atoms (or ions) of each element in the compound’s basic structural unit.
Water, for example, is a molecular compound; each molecule consists of two hydrogen atoms chemically bonded to an oxygen atom, giving H20 (read as “H-two-O”) molecules. Sodium chloride, or table salt, is an ionic compound, consisting of a network of oppositely charged ions (Na+ and C1-) held together by the forces of attraction between opposite electric charges.
Table sugar, vitamins, plastics, aspirin, penicillin, and many other materials important to you and your lifestyle have one thing in common. They are organic compounds, containing atoms of the element carbon, usually combined with each other and with atoms of other elements such as hydrogen, oxygen, nitrogen, sulfur, phosphorus, chlorine, and fluorine.
Among the millions of known organic (carbon-based) compounds are:
- Hydrocarbons–compounds of carbon and hydrogen atoms. An example is methane (CH4), the main component of natural gas.
- Chlorinated hydrocarbons–compounds of carbon, hydrogen, and chlorine atoms. Examples are DDT (C14H9Cl5) an insecticide, and PCBs (such as C12H5Cl5), oily compounds used as insulating materials in electric transformers.
- Chlorofluorocarbons (CFCs)–compounds of carbon, chlorine, and fluorine atoms. An example is Freon‑12 (CCl2F2), used as a coolant in refrigerators and air conditioners, as an aerosol propellant, and as a foaming agent for making some plastics.
- Simple carbohydrates (simple sugars)–certain types of compounds of carbon, hydrogen, and oxygen atoms. An example is glucose (C6H12O6), which most plants and animals break down in their cells to obtain energy.
Larger and more complex organic compounds, called polymers, consist of a number of basic structural or molecular units (monomers) linked together by chemical bonds. Some important types of organic polymers are:
- Complex carbohydrates–made up by linking together a number of simple‑sugar molecules such as glucose. Examples are the complex starches in rice and potato plants.
- Proteins–produced in cells by linking together different numbers and sequences of about 20 different monomers, known as amino acids. Each amino acid contains carbon, hydrogen, oxygen, and nitrogen atoms, and a few also contain sulfur. Most animals, including humans, can make about 10 of these amino acids in their cells. Sufficient quantities of the other 10, known as essential amino acids, must be obtained from food intake to prevent protein deficiency diseases.
Nucleic acids–made by linking together hundreds to thousands of four different types of monomers, called nucleotides, in different numbers and sequences. Nucleic acids contain carbon, hydrogen, oxygen, nitrogen, and phosphorus. Examples are various types of DNA and RNA in the cells of living organisms. A human cell contains 23 pairs of chromosomes, which together make up an individual’s entire genetic endowment. Genetic information coded in the structure of DNA molecules found in your chromosomes is what makes you different from an oak leaf, an alligator, or a flea and from your mother and father. This information is contained in various sequences of nucleotides in parts of various cellular DNA molecules. These distinctive DNA segments are called genes. DNA molecules can replicate themselves and contain the instructions for assembling each new cell from a few kinds of “lifeless” molecules and for assembling the proteins each cell needs to survive and reproduce.
RNA molecules help carry instructions provided by DNA molecules to parts of cells to produce proteins. DNA molecules can be viewed as a cell’s administrators, proteins as its workforce, and RNA molecules as middle‑level employees who carry and translate instructions from the administrator molecules needed to form the workforce molecules.
All other compounds are called inorganic com-pounds. Some of the inorganic compounds you will encounter in this book are sodium chloride (NaCI), water (H20), nitrous oxide (N2O), nitric oxide (NO), carbon monoxide (CO), carbon dioxide (C02),* nitrogen dioxide (NO2), sulfur dioxide (SO2), ammonia (NH3), sulfuric acid (H2SO4), and nitric acid (HNO3).
MATTER QUALITY Matter quality is a measure of how useful a matter resource is, based on its availability and concentration. High‑quality matter is organized and concentrated, and is usually found near the earth’s surface. It has great potential for use as a matter resource. Low‑quality matter is disorganized, dilute, or dispersed, and is often found deep underground or dispersed in the ocean or in the atmosphere. It usually has little potential for use as a matter resource (Figure 3‑4).
An aluminum can is a more concentrated, higher-quality form of aluminum than aluminum ore with the same amount of aluminum. That’s why it takes less energy, water, and money to recycle an aluminum can than to make a new can from aluminum ore.
Entropy is a measure of the disorder or randomness of a system. The greater the disorder of a sample of matter, the higher its entropy; the greater its order, the lower its entropy. Thus an aluminum can has a lower entropy (more order) than aluminum ore with the same amount of aluminum mixed with other materials. Similarly a piece of ice in which the water molecules are held in an ordered solid structure has a lower entropy (more order) than the highly dispersed water molecules in water vapor.
Energy: Types, Forms, and Quality
TYPES Like matter, energy affects every part of your life. You need it to keep your heart beating, to think, to breathe, to cook food, to travel by any method, and to warm or cool the buildings in which you live or work. Energy powers the factories, cars, bulldozers, airplanes, chain saws, giant power shovels, and electric motors and lights we use to improve our lives. Large amounts of energy are also used to extract metals from ores and to manufacture fertilizers, pesticides, plastics, CFCs, and other products.
Energy is the capacity to do work. You cannot pick up or touch energy, but you can use it to do work. You do work when you move matter, such as your arm or this book. Work or matter movement also is needed to boil liquid water and change it into steam or to burn natural gas to heat a house or cook food. Energy is also the heat that flows automatically from a hot object to a cold object. Touch a hot stove and you experience this energy flow in a painful way.
Energy comes in many forms: light; heat; electricity; chemical energy stored in the chemical bonds in coal, sugar, and other materials; moving matter such as water, wind (air masses), and joggers; and nuclear energy emitted from the nuclei of certain isotopes.
Scientists classify energy as either kinetic or potential. Kinetic energy is the energy that matter has because of its motion and mass. Wind (a moving mass of air), flowing streams, falling rocks, heat, electricity (flowing charged particles), and moving cars have kinetic energy.
Heat refers to the total kinetic energy of all the randomly moving atoms, ions, or molecules within a given substance, excluding the overall motion of the whole object. Temperature is a measure of the average speed of motion of the atoms, ions, or molecules in a sample of matter at a given moment. A substance can have a high heat content (much mass and many moving atoms, ions, or molecules) but a low temperature (low average molecular speed). For example, the total heat content of a lake is enormous, but its average temperature is low. On the other hand, a cup of hot coffee has a much lower heat content than a lake, but its temperature is much higher.
Radio waves, TV waves, microwaves, infrared radiation, visible light (the colors we see), ultraviolet radiation, X rays, gamma rays, and cosmic rays are forms of radiant energy traveling as waves and known as electromagnetic radiation. These forms of energy make up a wide band or spectrum of electromagnetic waves that differ in their wavelength (distance between two consecutive peaks or troughs) and energy content (Figure 3-5).
Cosmic rays, gamma rays, X rays, and ultraviolet radiation have enough energy to knock electrons from atoms and change them to positively charged ions. The resulting highly reactive electrons and ions can disrupt living cells, interfere with body processes, and cause many types of sickness, including various cancers. These potentially harmful forms of electromagnetic radiation are called ionizing radiation.
The other forms of electromagnetic radiation do not contain enough energy to form ions and are called nonionizing radiation. Some controversial evidence now suggests that long-term exposure to nonionizing radiation emitted by radios, TV sets, the video display terminals of computers, overhead electric power lines, electrically heated water beds, electric blankets, motors, and other electrical devices may also damage living cells.
Potential energy is stored energy that is potentially available for use. A rock held in your hand, an unlit stick of dynamite, still water behind a dam, and nuclear energy stored in the nuclei of atoms all have potential energy because of their position or the position of their parts. When you drop a rock held in your hand, its potential energy changes into kinetic energy. The chemical energy stored in molecules of gasoline and in the carbohydrates, proteins, and fats of food is also potential energy. When you burn gasoline in a car engine, the potential energy stored in the chemical bonds of its molecules changes into heat, light, and mechanical (kinetic) energy that propels the car.
An electric power plant burns fuel to make heat that is used to boil water into steam. The steam expands through turbines where its thermal energy (the energy of heat) is converted into kinetic energy. The turbines turn generators, and electromagnetic energy–electricity–comes out and is transmitted by wire to factories and buildings. When you flip a light switch you are at the end of the following energy chain: fuel ‑ heat ‑ steam ‑ kinetic energy ‑ electricity.
ENERGY RESOURCES USED BY PEOPLE Some 99% of the energy used to heat Earth and all our buildings comes directly from the sun. Without this direct input of solar energy Earth’s average temperature would be ‑240°C (‑400°F), and life as we know it would not have arisen. Solar energy also helps recycle the carbon, oxygen, water, and other chemicals we and other organisms need to stay alive and healthy.
Broadly defined, solar energy includes both perpetual direct energy from the sun and several forms of energy produced indirectly by the sun’s energy. These include wind, falling and flowing water (hydropower), and biomass (solar energy converted to chemical energy stored in the chemical bonds of organic compounds in trees and other plants). We use wind turbines and hydroelectric power plants to convert the indirect solar energy of wind and falling or flowing water into electricity.
Passive solar energy systems capture and store direct solar energy and use it to heat buildings and water without the use of mechanical devices. Examples are a well‑insulated, fairly airtight house with large insulating windows that face the sun and the use of rock, concrete, or water to store and release heat slowly.
Direct solar energy can also be captured by active solar energy systems. For example, specially designed roof‑mounted collectors concentrate direct solar energy; pumps then transfer this heat to water, to the interior of a building, or to insulated stone or water tanks that store and release heat slowly. Solar cells convert solar energy directly into electricity in one simple, nonpolluting step.
The 99% of energy that comes directly from the sun is not sold in the marketplace. The remaining 1%, the portion we generate to supplement the solar input, is commercial energy sold in the marketplace and noncommercial energy used by people who gather fuel wood, dung, and crop wastes for their own use. Most commercial energy comes from extracting and burning mineral resources in the earth’s crust (Figure 3‑6), primarily fossil fuels. Most sources of noncommercial energy are potentially renewable biomass such as wood, but they may not be harvested sustainably.
ENERGY QUALITY Energy varies in its ability to do useful work. Energy quality is a measure of usefulness (Figure 3‑9). High‑quality energy is organized or concentrated and has great ability to perform useful work. That is, it has low entropy. Examples of these useful sources of energy are electricity, coal, gasoline, concentrated sunlight, nuclei of uranium‑235, and heat concentrated in fairly small amounts of matter so that its temperature is high.
By contrast, low‑quality energy is disorganized or dispersed and has little ability to do useful work. That is, it has high entropy. An example is heat dispersed in the moving molecules of a large amount of matter, such as the atmosphere or a large body of water, so that its temperature is relatively low. For instance, the total amount of heat stored in the Atlantic Ocean is greater than the amount of high‑quality chemical energy stored in all the oil deposits of Saudi Arabia. However, the ocean’s heat is so widely dispersed that it can’t be used to move things or to heat things to high temperatures.
We use energy to accomplish certain tasks, each requiring a certain minimum energy quality. Electrical energy, which is very high-quality energy, is needed to run lights, electric motors, & electronic devices. We need high-quality mechanical energy to move a car, but we need only low-temperature air (less than 100C) to heat homes and other buildings.
It makes sense to match the quality of an energy source to the quality of energy needed to perform a particular task – this saves energy, and usually money.
Physical and Chemical Changes and the Law of Conservation of Matter
PHYSICAL AND CHEMICAL CHANGES A physical change is one that involves no change in chemical composition. For example, cutting a piece of aluminum foil into small pieces is a physical change – each cut piece is still aluminum. Changing a substance from one physical state to another is also a physical change. For example, when solid water, or ice, is melted or liquid water is boiled, none of the H20 molecules involved are altered; instead, the molecules are organized in different spatial patterns.
In a chemical change, or chemical reaction, there is a change in the chemical composition of the elements or compounds involved. Chemists use shorthand chemical equations to represent what happens in a chemical reaction. A chemical equation shows the chemical formulas for the reactants (starting chemicals) and the products (chemicals produced) with an arrow placed between them. For example, when coal burns completely, the solid carbon (C) it contains combines with oxygen gas (O2) from the atmosphere to term the gaseous compound carbon dioxide (CO2):
Energy is given off in this reaction, making coal a useful fuel. The reaction also shows how the burning of coal or any carbon containing compounds, such as those in wood, natural gas, oil, and gasoline, adds carbon dioxide gas to the atmosphere.
THE LAW OF CONSERVATION Of MATTER: THERE IS NO AWAY
Earth loses some gaseous molecules to space, and it gains small amounts of matter from space, mostly in the form of occasional meteorite and cosmic dust. These losses and gains of matter are minute compared with Earth’s total mass.
This means that Earth has essentially all the matter it will ever have. Fortunately over billions of years natural processes have evolved for continuously cycling key chemicals back and forth between the nonliving environment (soil, air, and water) and the living environment.
You, like most people, probably talk about consuming or using up material resources, but the truth is that we don’t consume matter. We only use some of Earth’s resources for a while. We take materials from the earth, carry them to another part of the globe, and process them into products. These products are used and then discarded, reused, or recycled.
We may change various elements and compound from one physical or chemical form to another, but in all physical and chemical changes we can’t create or destroy any of the atoms involved. All we can do is rearrange them into different spatial patterns (physical changes) or different combinations (chemical changes). This fact, based on many thousands of measurements of matter undergoing physical and chemical changes, is known as the law of conservation of matter. In describing chemical reactions chemists use a shorthand bookkeeping system to make sure no atoms are created or destroyed, as required by the law of conservation of matter.
The law of conservation of matter means that there is no “away”: Everything we think we have thrown away is still here with us in one form or another. We can collect dust and soot from the smokestacks of industrial plants, but these solid wastes must then be put somewhere. We can remove substances from polluted water at a sewage treatment plant, but the gooey sludge must either be burned (producing some air pollution), buried (possibly contaminating underground water supplies), or cleaned up and applied to the land as fertilizer (dangerous if the sludge contains non-degradable toxic metals, such as lead and mercury). Tall smokestacks can reduce some types of local air pollution but can increase air pollution in distant downwind areas. Banning DDT in the United States but still selling it abroad means that it can come back to us as DDT residues in imported coffee, fruit, fish, and other foods.
We can make the environment cleaner and convert some potentially harmful chemicals into less harmful, or even harmless, physical or chemical forms. Nevertheless, the law of conservation of matter means that we will always be faced with the problem of what to do with some quantity of wastes. By placing much greater emphasis on pollution prevention and waste reduction, however, we can greatly reduce the amount of wastes we add to the environment.
The First and Second Laws of Energy
FIRST LAW OF ENERGY: YOU CAN’T GET SOMETHING FOR NOTHING
After making millions of measurements, scientists have observed energy being changed from one form to another in physical and chemical changes, but they have never been able to detect any energy being created or destroyed. This summary of what happens in nature is called the law of conservation of energy, also known as the first law of energy or first law of thermodynamics. This law does not apply to nuclear changes, however, where energy can be produced from small amounts of matter. This law means that when one form of energy is converted to another form in any physical or chemical change, energy input always equals energy output: We can’t get something for nothing in terms of energy quantity.
SECOND LAW OF ENERGY: YOU CAN’T BREAK EVEN Because the first law of energy states that energy can be neither created nor destroyed, you might think that there will always be enough energy; yet, if you fill a car’s tank with gasoline and drive around, or if you use a flashlight battery until it is dead, you have lost something. If it isn’t energy, what is it? The answer is energy quality.
Countless experiments have shown that in any conversion of energy from one form to another, there is always a decrease in energy quality (the amount of useful energy). These findings are expressed in the second law of energy, or the second law of thermodynamics: When energy is changed from one form to another, some of the useful energy is always degraded to lower‑quality, more dispersed (higher‑entropy), less useful energy. This degraded energy is usually in the form of heat, which flows into the environment and is dispersed by the random motion of air or water molecules. In other words we can’t break even in terms of energy quality because energy always goes from a more useful to a less useful form. The more energy we use, the more low‑grade energy (heat), or entropy, we add to the environment. No one has ever found a violation of this fundamental scientific law.
Consider three examples of the second energy law in action. First, when a car is driven, only about 10% of the high‑quality chemical energy available in its gasoline fuel is converted into mechanical energy to propel the vehicle and into electrical energy to run its electrical systems. The remaining 90% is degraded heat that is released into the environment and eventually lost into space. Second, when electrical energy flows through filament wires in an incandescent light bulb, it is changed into about 5% useful light and 95% low‑quality heat that flows into the environment. What we call a light bulb is really a heat bulb.
The second energy law also means that we can never recycle or reuse high‑quality energy to perform useful work. Once the concentrated energy in a piece of food, a liter of gasoline, a lump of coal, or a chunk of uranium is released, it is degraded to low‑quality heat that becomes dispersed in the environment. We can heat air or water at a low temperature and upgrade it to high‑quality energy, but the second energy law tells us that it will take more high‑quality energy to do this than we get in return.
LIFE AND THE SECOND ENERGY LAW Life represents a creation and maintenance of ordered structures. Thus you might be tempted to think that life is not governed by the second law of thermodynamics.
However, to form and preserve the highly ordered arrangement of molecules and the organized network of chemical changes in your body, you must continually get and use high‑quality matter and energy resources from your surroundings. As you use these resources, you add low‑quality (high‑entropy) heat and waste matter to your surroundings. For example, your body continuously gives off heat equal to that of a 100-watt light bulb; this is the reason a closed room full of people gets warm. You also continuously give off molecules of carbon dioxide gas and water vapor, which become dispersed in the atmosphere.
Planting, growing, processing, and cooking food all require high-quality energy and matter resources that add low-quality (high-entropy) heat and waste materials to the environment. In addition, enormous amounts of low-quality heat and waste matter are added to the environment when concentrated deposits of minerals and fuels are extracted from the earth’s crust, processed, and used to make roads, clothes, shelter, and other items or burned to heat or cool buildings or to transport you. All forms of life are tiny pockets of order (low entropy) maintained by creating a sea of disorder (high entropy) in their environment.
Because of the second energy law, the more energy we use (and waste), the more disorder (entropy) we create in the biosphere. The second law of energy tells us that we can’t avoid this entropy trap, but we can reduce or minimize our production of entropy. This is the reason that reducing energy waste and switching from harmful nonrenewable energy resources to less harmful renewable and perpetual energy resources are the keys to a sustainable future for us and many other species.
Energy Efficiency and Net Useful Energy
INCREASING ENERGY EFFICIENCY You may be surprised to learn that only 16% of all commercially produced energy that flows through the U.S. economy performs useful work or is used to make petrochemicals, which in turn are used to produce plastics, medicines, and many other products. This means that 84% of all commercial energy used in the United States is wasted. About 41 % of this energy is wasted automatically because of the degradation of energy quality imposed by the second energy law. However, about 43% is wasted unnecessarily mostly by using fuel-wasting motor vehicles, furnaces, and other devices and by living and working in leaky, poorly insulated buildings.
Much of this unnecessary energy waste can be eliminated by increasing the energy efficiency of the energy conversion devices we use. This is the percentage of total energy input that does useful work and is not converted to low-quality, essentially useless heat in an energy conversion system. The energy conversion devices we use vary considerably in their energy efficiencies.
We can save energy and money by buying the most energy‑efficient home heating systems, water heaters, cars, air conditioners, refrigerators, and other household appliances available. The energy‑efficient models may cost more, but in the long run they usually save money by having a lower life‑cycle cost: initial cost plus lifetime operating costs.
The net efficiency of the entire energy delivery process for a space heater, water heater, or car is determined by finding the efficiency of each step in the energy conversion process. For example, the sequence of energy‑using and energy‑wasting steps involved in using electricity produced from fossil or nuclear fuels is extraction – transportation ‑ processing ‑ transportation to power plant ‑ electric generation – transmission ‑ end use.
Figure 3‑17 shows how net energy efficiency is determined for heating a well‑insulated home (1) with electricity produced at a nuclear power plant, transported by wire to the home, and converted to heat (electric resistance heating), and (2) passively with an input of direct solar energy through windows facing the sun, with heat stored in rocks or water for slow release. This analysis shows that the process of converting the high-quality energy in nuclear fuel to high‑quality heat at several thousand degrees, converting this heat to high-quality electricity, and then using the electricity to provide low‑quality heat for warming a house to only about 20°C (68°F), is extremely wasteful of high-quality energy. Burning coal, or any fossil fuel, at a power plant to supply electricity for space heating is also inefficient. By contrast, it is much less wasteful to use a passive or active solar heating system to obtain low‑quality heat from the environment, store it in stone or water, and – if necessary – raise its temperature slightly to provide space heating or household hot water.
Using high‑quality electrical energy to provide low‑quality heating for living space or household water is like using a chain saw to cut butter or a sledgehammer to kill a fly. As a general rule, we should match energy quality to energy tasks: Don’t use high‑quality energy to do a job that can be done with lower‑quality energy.
Figure 3‑18, p 20 lists the net energy efficiencies for a variety of space‑heating systems. It shows that the most energy‑efficient form of space heating is a superinsulated house. The most wasteful (least efficient) and most expensive way to heat a house is with electricity produced by a coal‑burning power plant or a nuclear power plant. To prevent buildup of indoor air pollutants, any house should be equipped with an air‑to‑air heat exchanger. Use of such a device reduces slightly each of the net energy efficiencies shown in Figure 3‑18.
Heat pumps are useful for space heating in warm climates (where they aren’t needed much), but not in cold climates because they then switch to wasteful, costly electric resistance heating. Also, most heat pumps in their air conditioning mode are much less efficient than many available stand‑alone air conditioning units. Most heat pumps also require expensive repair every few years.
A similar analysis of net energy efficiency shows that the least efficient and most expensive way to heat water for washing and bathing is to use electricity produced by any type of power plant. The most efficient method is to use a tankless instant water heater fired by natural gas or liquefied petroleum gas (LPG). Such heaters are about the size of a bookcase loudspeaker and burn fuel only when the hot‑water faucet is turned on. They heat the water instantly as it flows through a small burner chamber and provide hot water only when, and as long as, it is needed. Tankless heaters are widely used in many parts of Europe and are slowly beginning to appear in the United States. A well-insulated, conventional natural gas or LPG water heater is also fairly efficient, although all conventional natural gas and electric resistance heaters keep a large tank of water hot all day and night and can run out after a long shower or two.
In 1991 the average price of obtaining 250,000 kilocalories (1 million Btus) for heating space or water in the United States was $6.05 using natural gas, $7.56 using kerosene, $9.30 using oil, $9.74 using propane, and $24.15 using electricity. As these numbers suggest, if you like to throw away hard‑earned dollars, use electricity to heat your house and bath water.
Perhaps the three least efficient energy‑using devices in widespread use today are (1) incandescent light bulbs (which waste 95% of the energy input), (2) vehicles with internal combustion engines (which waste 90% of the energy in their fuel), and (3) nuclear power plants producing electricity for space or water heating (which waste 86% of the energy in their nuclear fuel; Figure 3‑17). These devices were developed when energy was cheap and plentiful. To help sustain the earth and ourselves, we will have to replace them or greatly improve their energy efficiency.
USING WASTE HEAT We cannot recycle high‑quality energy, but we can slow the rate at which waste heat flows into the environment when high‑quality energy is degraded.
The best way to do this is to heavily insulate a house and eliminate air leaks; then equip it with an air-to-air heat exchanger to prevent buildup of indoor air pollutants.
In some office buildings and stores waste heat from lights, computers, and other machines is collected and distributed to reduce heating bills during cold weather and is exhausted to reduce cooling bills during hot weather. Waste heat from industrial plants and electrical power plants can be distributed through insulated pipes and used to heat nearby buildings, greenhouses, and fish ponds, as is done in some parts of Europe.
Another way to use waste heat produced by industrial plants is cogeneration, the production of two useful forms of energy such as steam and electricity from the same fuel source. Waste heat from coal-fired and other industrial boilers can be used to produce steam that spins turbines and generates electricity at half the cost of buying it from a utility company. The electricity can be used by the plant or sold to the local power company for general use. Cogeneration is used in many industrial plants throughout Europe. If all large industrial boilers in the United States used cogeneration, there would be no need to build any electric power plants until 2020.
NET USEFUL ENERGY: IT TAKES ENERGY TO GET ENERGY
The usable amount of high-quality energy from a given quantity of an energy resource is its net useful energy. It is the total useful energy available from the resource over its lifetime minus the amount of energy used (the first energy law), automatically wasted (the second energy law), and unnecessarily wasted in finding, processing, concentrating, and transporting it to users. For example, if 9 units of fossil fuel energy are needed to supply 10 units of nuclear, solar, or additional fossil fuel energy (perhaps from a deep well at sea), the net useful energy gain is only 1 unit of energy.
We can express this relationship as the ratio of useful energy produced to the useful energy used to produce it. In the example just given, the net energy ratio would be 10/9, or approximately 1.1. Thus the higher the ratio, or the equivalent real number, the greater the net useful energy yield. When the ratio is less than 1, there is a net energy loss over the lifetime of the system.
Currently oil has a relatively high net useful energy ratio because much of it comes from large, accessible deposits such as those in Saudi Arabia and other parts of the Middle East. When those sources are depleted, however, the net useful energy ratio of oil will decline and prices will rise. Then more money and more high‑quality fossil fuel will be needed to find, process, and deliver new oil from widely dispersed small deposits and deposits buried deep in the earth’s crust or located in remote areas like Alaska, the Arctic, and the North Sea.
Conventional nuclear fission energy has a low net energy ratio because large amounts of energy are required to extract and process uranium ore, to convert it into a usable nuclear fuel, and to build and operate power plants. Energy is also needed to dismantle the plants after their 25‑30 years of useful life and to store the resulting highly radioactive wastes for thousands of years.
Matter and Energy Laws and Environmental and Resource Problems
THROWAWAY SOCIETIES Because of the law of conservation of matter and the second law of energy, resource use by each of us automatically adds some waste heat and waste matter to the environment. Your individual use of matter and energy resources, and your additions of waste heat and matter to the environment, may seem small and insignificant. But you are only one of the 1.2 billion individuals in the MDCs using large quantities of and energy resources at a rapid rate. Meanwhile, 4.3 billion people in less developed countries hope to be able to use more of these resources. And each year there are 94 million more consumers of Earth’s energy and matter resources. Projected population growth alone will lead to a 70% jump in global energy use by 2025, even if per capita energy use stays at current levels. High rates of economic growth could triple energy use by 2025.
Most of today’s advanced industrialized countries are largely one‑way societies, or throwaway societies, sustaining continued economic growth by increasing the flow or throughput of planetary sources of materials and energy, through the economy, to planetary sinks (air, water, soil, organisms) where pollutants and wastes end up. The scientific laws of matter and energy tell us that if more and more people continue to use and waste more and more energy and matter resources at an increasing rate, sooner or later the capacity of the local, regional, and global environments to dilute and degrade waste matter and absorb waste heat will be exceeded.
MATTER‑RECYCLING SOCIETIES A stopgap solution to this problem is to convert from a throwaway society to a matter‑recycling society. The goal of such a shift would be to allow economic growth to continue without depleting matter resources and without producing excessive pollution and environmental degradation. As we have learned, however, there is no free lunch when it comes to energy.
The two laws of energy tell us that recycling matter resources always requires high‑quality energy, which cannot be recycled. In the long run a matter‑recycling society based on continuing economic growth must have an inexhaustible supply of affordable high‑quality energy. The environment must also have an infinite capacity to absorb and disperse waste heat and to dilute and degrade waste matter. Also, there is a physical limit to the number of times some materials, such as paper fiber, can be recycled before they become unusable. Thus shifting from a throwaway society to a matter‑recycling society is only a temporary solution to our problems. Nevertheless, making such a shift is necessary to give us more time to convert to a sustainable‑Earth society.
Suppose that affordable solar cells, nuclear fusion at room temperature, solar‑produced hydrogen, or some other breakthrough were to guarantee an essentially infinite supply of affordable useful energy. Would that solve all our environmental and resource problems? No! The second energy law tells us that the faster we use energy to transform matter into products and to recycle those products, the faster low‑quality heat and waste matter are dumped into the environment. Thus the more we use energy to “conquer” Earth, the more stress we put on the environment. Experts argue over how close we are to environmental overload, but the scientific laws of matter and energy indicate that limits do exist.
SUSTAINABLE EARTH SOCIETIES: The three scientific laws governing matter and energy changes indicate that the best long‑term solution to our environmental problems is to shift from a society based on maximizing matter and energy flow (throughput) to a sustainable‑Earth society.
Using these lessons from nature as guidelines, a sustainable‑Earth society would:
- Reduce the throughput of matter and energy resources to prevent excessive depletion anddegradation of planetary sources and overload of planetary sinks
- Use energy more efficiently, and not use high-quality energy for tasks that require only moderate quality energy
- Shift from exhaustible and potentially polluting fossil & nuclear fuels to less harmful perpetual and renewable energy obtained from the sun and from Earth’s natural cycles and flows
- Not waste potentially renewable resources, and use them no faster than the rate at which they are regenerated
- Not waste nonrenewable resources, and use them no faster than the rate at which a renewable resource, used sustainably, can be substituted for it
- Recycle and reuse at least 80% of the matter we now discard as trash
- Reduce use and waste of matter resources by making things that last longer and are easier to recycle, reuse, and repair
- Add wastes and pollutants to environmental sinks no faster than the rate at which they can be recycled, reused, absorbed, or rendered harmless to us and other species by natural processes
- Emphasize pollution prevention and waste reduction instead of pollution cleanup and waste management
- Bring human population growth to a halt to reduce stress on global life support systems
- Eliminate poverty, which degrades humans and the environment by forcing people to use resources unsustainably to stay alive