Week 3 Notes
Week 3 Notes ENVT 0845-005
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This 9 page Class Notes was uploaded by Katrina Salamon on Friday January 29, 2016. The Class Notes belongs to ENVT 0845-005 at Temple University taught by Dr. Udoeyo in Winter 2016. Since its upload, it has received 51 views. For similar materials see The Environment in Professional Education Services at Temple University.
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Date Created: 01/29/16
Chapter 3: The Physical Science of the Environment Searching for life elsewhere Looking for life o Probes sent to space o Mars: new focus Viking ½ Evidence of water encouraging because all organisms require water to live Martian soil samples—carbon dioxide was released in abundance in one of the samples Debate continues Our focus in this chapter is to explore the basic principles of chemistry and energy transfer that characterizes life on earth o Mendeleev (Russian chemist) created the periodic table Chemicals are the raw materials that make up our bodies, the bodies of other organisms, and the physical environment. Life’s chemistry is tied to water o Life first evolved in the water o All living organisms require water o Cells consist of about 75% water Atoms o Each element consists of one kind of atom o An atom is the smallest unit of matter that still retains the properties of an element o Atoms are composed of o Protons (the number you see on the element) Positively charged particles Located in the nucleus o Neutrons Neutral particles Located in the nucleus o Electrons Negatively charged particles Found in orbitals surrounding the nucleus The negative charge of electrons and the positive charge of protons keep electrons near the nucleus The number of protons is the atoms atomic number An atoms mass number is the sum of the number of protons and neutrons Elements are made up of one type of atom An element is a substance that cannot be broken down to other substances by ordinary chemical means Number of protons determine characteristics and name 92 naturally occurring elements Represented by a symbol o C: carbon o O: oxygen o N: nitrogen o H: hydrogen Theses 4 element play important roles in ecosystems These make up a human being or any other organism Isotopes: element with different numbers of neutrons Different isotopes of an element have the same number of protons but different numbers of neutrons Some isotopes have nuclei that are unstable and break apart (radioactive) In radioactive isotopes, the nucleus decays spontaneously, giving off particles and high energy protons, neutrons, electrons and radiation Half life: time it takes for one half of the atoms in a sample to decay Isotopes can form radiation, change to other things. Radioactive Isotopes: radioactive tracers are frequently used in medical diagnosis o An imaging instrument that uses positronemission tomography (PET) detects the location of injected radioactive materials o PET is useful for diagnosing heart disorders and cancer and in brain research o In addition to benefits, there are dangers associated with using radioactive substances Uncontrolled exposure can cause damage to some molecules in a living cell, especially DNA Chemical bonds are broken by the emitted energy, which causes abnormal bonds to form The radiation exposure in the Ukraine caused those exposed to have children with birth defects. Molecules: tw or more atoms held together by covalent bonds. o Oxygen (O2, Nitrogen (N2) Compounds o Molecules made from more than one element o Carbon dioxide (CO2), water, H2O) Chemical bonds hold molecules together o Covalent bonds: the sharing of a pair of outer shell electrons by two atoms. It is a strong bond. Some molecules share electrons equally Molecule nonpolar (nonopolar bond) o Example: O2 Atoms in a molecule do not always share electrons equally. Oxygen is much more electronegative than hydrogen, meaning that it attracts electrons more strongly. o Molecule polar, resulting in partial charges (polar bond) Example: H2O A molecule of oxygen gas is held together by a double covalent bond—two shared pairs of electrons equally Water is one of the simplest molecules. It is made of three linked atoms, (H2O) Ionic Bond: two ions with opposite charges attract each other. o When the attraction holds the ions together, it is called an ionic bond. o Salt is a synonym for an ionic compound. Strong bond Electron transferred between atoms Termed ionic compound or salts Sodium donating electron has a net (+) charge Chlorine receiving electron has a net () charge Dipole Bonds: weaker bonds as a consequence of shifts in electrical charge The Polarity of water molecules causes them to be attracted to each other. o Weaker Bonds: one of the most important types of weak bonds is the hydrogen bond, which is best illustrated with water molecules. o Hydrogen bonds give water high surface tension, making it behave as if it were coated with an invisible film o Many biological functions Water: important to life. Water is a polar molecule, that is, it has an unequal distribution of charges. o Forms dipole bonds with other water molecules o Gives water unique properties, stability An excellent solvent o Many biological functions use water as solvent Water organizes nonpolar molecules o Hydrophilic “waterloving” o Hydrophobic “waterfearing” o Water causes hydrophobic molecules to aggregate or assume specific shapes Water molecules may break apart into hydrogen ions (H+) and Hydroxyl ions (OH) H2O OH (hydroxide ion) + H+ (Hydrogen ion) Water can exist as a gas, liquid, or solid Water is less dense as a solid than a liquid because of hydrogen bonding. When liquid water becomes colder, more hydrogen bonds form—water becomes denser as it cools As liquid water heats, the hydrogen bonds weaken Ice hydrogen bonds are stable Water is important to life o Acids and bases Water dissociates into H+ and OH Chemicals (acid/base) may shift amounts Shift measured by pH scale A substance that donates hydrogen ions to solutions is called an acid A base is a substance that reduces the hydrogen ion concentration of a solution The pH scale describes how acidic or basic a solution is. It is a quantitative representation of the relative amounts of acid and base Chemistry of the Environment A substance that donates hydrogen ions to solutions is called an acid. A base is a substance that reduces the hydrogen ion concentration of a solution. The pH scale describes how acidic or basic a solution is. It is a quantitative representation of the relative amounts of hydrogen and hydroxyl ions in a liquid. The pH scale ranges from 014, with 0 the most acidic and 14 the most basic. Each pH unit represents a 10fold change in the concentration of H in a solution. Organic Molecules Organic molecules are made of carbon molecules. Carbon based molecules are called organic compounds. All organic molecules such as carbohydrates, fats, and proteins, contain the element carbon. o Carbon atom covalently bonded to hydrogen and other atoms o Primary structural and function component of life o Range in size Inorganic molecules not made of carbon and hydrogen. Organic molecules: types o Hydrocarbons Only made of carbon and hydrogen Methane is the simplest hydrocarbon o Carbohydrates: includes sugars and polymers of sugars. These molecules are used as building materials and sources of energy Made of carbon, hydrogen and oxygen Sugars, (CH 2O)n, with the n between 3 and 7 Glucose (C 6 O12 6he basic form of energy for most organisms Sugars known as saccharides. o Lipids: long chains of carbon and hydrogen and a shorter region with one to several oxygen molecules. The membranes around and within cells are made mostly of phospholipids. Cholesterol, a type of lipid called a steroid, is also a component of membranes. o Fats: butter, lard, margarine, and oils o Saturated (Single bonds) and unsaturated fats (double bonds) o Saturated fats in the diet can lead to heart disease, while unsaturated fats are safer o Longer region: nonpolar (not soluble in water), shorter region—polar o Lipids not water soluble o Important energy storage Macromolecules: small organic molecule linked together Polymers: linked together in long chains Polysaccharides o Polymers of simple sugars Starch Cellulose The bonds in cellulose can only be broken by a few kids of microorganisms Macromolecules: o Proteins: Amino group (NH )2 Twenty different amino acids are used to build proteins Carboxylic acid group (COOH) Keratin that makes up fingernails and hair, provide structure. o Proteins made of chains of 100 to 1,000+ amino acids. Macromolecules o Proteins o Fold to particular shapes yielding function o Structural or functional o May act as catalysts Termed enzymes (enzymes make a reaction go faster, it doesn’t actually participate in the reaction) Almost all biological reactions use enzymes. Nucleic Acids o Polymers of nucleotides 5carbon sugar, phosphate group, and nitrogenous base o Deoxyribonucleic acid (DNA) Hereditary material Traits coded in sequence of bases Adenine (A), thymine (T), cytosine (C), and guanine (G) Genes carry the code used to build specific proteins Genome: an organism’s complete set of DNA o Ribonucleic acid (RNA) Structure similar to DNA Protein Synthesis Transcription o DNA code to RNA Translation o RNA code to protein o Triplet sequences code for amino acids—START— AUG o STOP—UAG, UGA, UAA Energy: Capacity to do work o Work: force applied to an object over a distance o Potential energy: stored energy o Kinetic energy: energy in motion Laws of Thermodynamics: o First law: energy can be neither created nor destroyed; can be transformed. o Second Law: Energy transformations increase disorder Entropy: disorder Energy is often lost as heat Forms of Energy: four types important for ecosystems o Electromagnetic radiation Energy moves as photons in waves Electromagnetic spectrum—entire range of wavelengths Gamma rays, Xrays, and UV light have short wave length—can break bonds and are harmful Visible light Infrared, microwaves, radio waves with longer wavelength less harmful o Heat: when energy is converted from potential energy to kinetic energy, some of the energy can be used to do work, but some energy ends up as heat. Kinetic energy of molecules Temperature: Measure the average kinetic energy Farenheit scale—water freezes at 32, boils at 212 Celcius scale: sets 0 degree at the freezing point of water and 100 as the boiling point Environmental scientists prefer to express temperature in celcius Heat can move in four ways: Conduction: direct transfer of heat due to collisions of molecules Convection: warm regions become dense casues liquid to circulate Radiation: release of electromagnetic energy Latent Heat Transfer: highest kinetic energy evaporate o Chemical Energy: Our bodies use chemical energy from food to perform work Chemical energy: potential energy Breaking and forming chemical bonds o Photosynthesis assembles carbohydrates o Potential energy in glucose bonds o When needed, energy is released by respiration o Nuclear Energy Energy in the structure of matter Mass contain enormous of energy Transformation of mass to energy occurs by two processes: fission and fusion. o Nuclear fission Nucleus of the atom splits, creating two smaller atoms and releasing vast amounts of kinetic and electromagnetic energy (neutrons striking uranium isotope can cause the atoms to split) o Nuclear Fusion When atoms collide and fuse, forming an atom of a new element Process that powers the sun Units of Energy o Energy is measured in different units: Joule (J): energy to support 1kg mass Calorie (cal): energy to raise 1g of water 1degree Celsius Watthour (Wh): amount of electricity used for an hour at 1 joule per hour SLIDE EARTH’S STRUCTURE o Mantle: above core, 70% of Earth’s volume, rich in elements magnesium and silicon. o Crust Thin surface layer of relatively light rock <1% of earth’s volume only part that directly interacts with living systems o (in order from center of the earth: inner solid core, outer core, lower mantle, upper mantle, oceanic crust, continental crust) o Lithosphere Crust and upper part of mantle that interacts with it. Building and moving continents o Crust is slowly moving o Tectonic plates Pieces of crust that float on mantle o Contents embedded in plates Tectonic plates meet at boundaries Transform Fault Boundaries o Plates slide past o Sites of earthquakes Divergent boundaries o Plates spread apart o Midatlantic plate separates the North American plate from Eurasian plate Convergent boundaries o Plates come together o Collision produced apalachian mountains, Himalayas, etc. Earth has gravity to hold atmosphere Earth’s unique atmosphere supports life o Compsition of gasses: 78% nitrogen 21 oxygen .slide Layers of atmosphere o Troposphere Lowerst layer, life located here, temperature drops with elevation o Stratosphere 1148 km, temperature increases approaching ozone, ozone layer located here (which protects life from ultraviolet radiation) o Mesosphere Above stratosphere, air temperature drops again (173 degrees C) at 90 km. o Thermosphere Extends out to space, above 150 km, gas density so low no friction, international space station orbits here, aurora occurs here. Water in the atmosphere o Water vapor (H 0)21% of molecules, varies predictably o Vapor pressure About 10 millibars (mb) at sea level, ranges 0.01 mb40+mb Saturation Vapor pressure o Temperature dependent Amount of water air can hold raises with temperature o Above saturation vapor pressure, water condenses to liquid forming rain, fog Relative humidity o Extent air is saturated with water o Relative humidity of a mass rises and falls with its temperature o If humidity increases, perspiration evaporates more slowly o Low humidity: perspiration evaporates quickly cooling the body o Expressed as a percentage Dew Point o Temperature where humidity is 100%
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