Science, Matter, and Energy Chapter 2

Key Concepts Science is a process for understanding The universe and environment are composed of matter and run with energy Scientific laws govern matter and energy * This chapter is a review of the basic interdisciplinary sciences that support study of environmental science.

W HAT D O SCIENTISTS DO ? Section 2-1

The Scientific Process/Method: Case study

Scientific Process: an experimental search for order in nature Hypothesis (idea) v. Theory (widely tested and accepted) vs. Law (widely tested fact) Need creativity, skepticism, reproducibility, and peer review.

The results of science can be tentative, reliable, or unreliable Tentative or frontier science = disagreement among scientists, results that have not been widely tested or are not widely accepted Reliable science = widely accepted by all or most expert scientists: consensus science Unreliable science = not been rigorously peer reviewed or that has been discarded as a result of peer review. EX: Junk science - Untested ideas presented as sound science- can be used to mislead for political gain

Questions to ask to determine if scientific findings are reliable or unreliable Was the experiment well designed? Did it involve a control group? Have other scientists reproduced the results? Does the proposed hypothesis explain the data? Are there no other, more reasonable explanations of the data? NOTE: Science has limitations! -error, human bias, unknown variables, etc.

W HAT IS MATTER AND WHAT HAPPENS WHEN IT UNDERGOES CHANGE ? Section 2-2

Matter What is matter? = anything with mass, takes up space. Physical forms: solid, liquid or gas. Chemical forms: 1. Elements = made of one type of atom = smallest unit of matter 2. Compounds/ Molecules = 2 or more elements bonded chemically (formulas)

Levels of Organization of Matter

Atoms Subatomic particles Protons Neutrons Electrons Atomic number = # of protons Mass number = # neutrons + # protons Isotopes = elements w/ same atomic number, but different mass number (different # neutrons)

Case study: Loss of Nitrate Ions from a Deforested Watershed

Chemistry Compounds = 2 or more bonded atoms ion = charged atom(s) pH = measure of acidity based on the amount of hydrogen ions (H + ) and hydroxide ions (OH - ) in a solution. A neutral solution has a pH of 7. A pH below 7 is an acidic solution, or acid. A pH above 7 is a basic solution, or base.

Organic compounds are the chemicals of life Organic compounds contain at least two carbon atoms combined with various other atoms. Methane (CH 4 ) is an exception; it is considered an organic compound although it has only one carbon atom. All other compounds are called inorganic compounds.

Organic Compounds contain at least 2 or more C atoms combined with each other + atoms of 1 or more other elements. Hydrocarbons: ex. CH 4 Chlorinated hydrocarbons: ex. DDT Monomers: Simple carbohydrates (simple sugars) ex. C 6 H 12 O 6 Polymers/Macromolecules = monomers linked together; 3 types 1. Complex carbohydrates 2. Proteins 3. Nucleic acids (DNA and RNA) 4. Lipids Organic

Matter comes to life through genes, chromosomes, and cells All living organisms are made of cells. Cells are fundamental structural and functional units of life. DNA contains sequences of nucleotides that form genes that code for traits. Thousands of genes make up chromosomes, which are composed of DNA and proteins

Matter Quality High-quality matter- concentrated, found near earth’s surface, useful Low-quality matter - dilute, not easily accessible, not useful Material efficiency (resource productivity) = total amount of material needed to produce each unit of good or service - Area for improvement

Matter undergoes physical, chemical, and nuclear changes Physical change is not chemical composition change but a change in states, such as ice melting or water freezing. Chemical change or chemical reaction is a change in the chemical composition.

Law of Conservation of Matter Matter is not destroyed Matter only changes form There is no “throwing away”

Matter and Pollution Harm Caused by Pollution Dependent on 3 factors: 1. Chemical nature of pollutants 2. Concentration 3. Persistence = length of time pollutant stays in air, water or body Degradable (nonpersistent) pollutants - broken down by natural processes :) Biodegradable pollutants - :) broken down by decomposers (sewage) Slowly degradable (persistent) pollutants - take decades or longer to degrade (plastics, DDT) :( Non-degradable pollutants - not broken down by natural processes (Pb, Hg, As) :(

Types of Nuclear Changes Matter can change form--into energy: E=mc2 Radioactive Decay: occurs naturally Fission: used for electrical generation: U- 235, persistent environmental impacts! Critical Mass = amount of fissionable nuclei needed to sustain a chain reaction Chain Reaction = releases an enormous amount of energy Fusion: used for modern bombs Uncontrolled - thermonuclear weapons Controlled - produce heat for electricity still experimental FOR A RADIOACTIVE ISOTOPE TO BE CONSIDERED SAFE, IT MUST HAVE DECAYED FOR AT LEAST 10 HALF LIVES !

Fig. 2-7a, p. 34 Radioactive decay occurs when nuclei of unstable isotopesspontaneously emit fast-moving chunks of matter (alpha particles orbeta particles), high- energy radiation (gamma rays), or both at afixed rate. A particular radioactive isotope may emit any one or acombination of the three items shown in the diagram. Radioactive isotope Radioactive decay Gamma rays Alpha particle Beta particle (electron)

Fig. 2-7b, p. 34 Nuclear fission Uranium-235 Neutron Energy Fission fragment n n n n n n Energy Fission fragment Nuclear fission occurs when the nuclei of certain isotopes with large mass numbers (such as uranium-235) are split apart into lighter nuclei when struck by a neutron and release energy plus two or three more neutrons. Each neutron can trigger an additional fission reaction and lead to a chain reaction, which releases an enormous amount of energy very quickly.

Fig. 2-7c, p. 34 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. Hydrogen-3 (tritium nucleus) 100 million °C Reaction conditions Neutron Energy Products Neutron Nuclear fusion Fuel Hydrogen-2 (deuterium nucleus) Helium-4 nucleus Proton

W HAT IS ENERGY AND WHAT HAPPENS WHEN IT UNDERGOES CHANGE ? Section 2-3

Energy Definition: The ability to do “work” and transfer heat Kinetic- motion, heat, electromagnetic radiation Potential-stored, can become kinetic (gasoline, water behind a dam)

Energy comes in many forms Solar energy is major source of renewable energy. It provides about 99% of the energy that heats the earth and provides living things with food (through photosynthesis by plants). Indirect forms of renewable solar energy include wind, hydropower and biomass. Non-renewable fossil fuels provide the other 1% of the energy used by the earth.

Some types of energy are more useful than others High-quality energy is concentrated and has a high capacity to do useful work. Low-quality energy is dispersed and has little capacity to do useful work.

Very high High Moderate Low Electricity Very high temperature heat (greater than 2,500°C) Nuclear fission (uranium) Nuclear fusion (deuterium) Concentrated sunlight High-velocity wind High-temperature heat (1,000–2,500°C) Hydrogen gas Natural gas Gasoline Coal Food Normal sunlight Moderate-velocity wind High-velocity water flow Concentrated geothermal energy Moderate-temperature heat (100–1,000°C) Wood and crop wastes Dispersed geothermal energy Low-temperature heat (100°C or lower) Very high-temperature heat (greater than 2,500°C) for industrial processes and producing electricity to run electrical devices (lights, motors) Mechanical motion (to move vehicles and other things) High-temperature heat (1,000–2,500°C) for industrial processes and producing electricity Moderate-temperature heat (100–1,000°C) for industrial processes, cooking, producing steam, electricity, and hot water Low-temperature heat (100°C or less) for space heating Relative Energy Quality (usefulness) Source of EnergyEnergy Tasks Fig. 2-10, p. 31 Energy Quality

Energy changes are governed by two scientific laws The first law of thermodynamics, or the law of conservation of energy, states that when energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed. The second law of thermodynamics states that when energy is changed from one form to another, energy quality is depleted.

First Law of Thermodynamics Energy is not created or destroyed Energy only changes form Can’t get something for nothing Energy input = Energy output

Second Law of Thermodynamics In every transformation, some energy quality is lost You can’t break even in terms of energy quality Second Law greatly affects life EXAMPLES: Cars: only 20-25% gasoline produces useful energy Ordinary light bulb: 5% energy is useful light, rest is low- quality heat Living systems: quality energy lost with every conversion

Solar energy Chemical energy (photosynthesis) Chemical energy (food) Mechanical energy (moving, thinking, living) Waste heat Waste heat Waste heat Waste heat Fig. 2-11, p. 32 Second Law of Thermodynamics

Matter and Energy Change: Laws and Sustainability Industrialization: Unsustainable high- throughput (high-waste) economies Recent modernization: Matter-recycling- and-reuse economy Future?: Sustainable low-throughput (low-waste) economies-- Lessons from Nature (sun, biodiversity, cycles)

Three Big Ideas Three scientific laws govern what we can and cannot do with matter and energy There is no “away” (law of conservation of matter). You cannot get something for nothing (1 st law of thermodynamics). You cannot break even (2 nd law of thermodynamics).