Worldview: what the world means to me (and my kind) Religion Resource abundance Standard of living Interaction with outgroups Government Education Personal background And.? Religion (2000) 84% of the world is religious (5 billion people). 2/3 belong to the big three Christian: 33%, (2 billion) Islam: 20%, 1.2 billion Hindu: 14 %, 800 million Quality of life indicators GDP (Gross Domestic Product) Life expectancy Infant mortality Drinking water Female Literacy Birthrate (fertility rates) 1-6 1
Haiti and Costa Rica: a case study History Religion Occupation Government Status today How we think, what we believe, how we are governed, all influence how we behave, including our behavior towards our environment What s a system Network of interdependent components and processes with materials and energy flowing from one component to another. These processes are biological, physical and chemical. Ultimately, the amount of energy and matter in vrs. what goes out, affects what can be supported in a system: open vrs. closed systems Let s take a look at these components Systems cont. Open systems most are to some degree. Some inputs are also output Closed systems exchange no matter or energy with surroundings (rare) Some systems (eg. Large ones) can absorb large inputs without altering much. But most have a threshold that can be difficult to measure/predict Feedback loops: ecological, physiological Positive feedback: positive change in a state variable (eg. Nutrient input) leads to a positive response (higher growth etc.). These can run away if not controlled. Eutrophication. Negative feedback: Increase leads to decrease too many predators=few prey=lower population of predators. These can lead to stability (homeostasis) What is an ecosystem in balance? Resilience Phase (state) shifts Stability? 2
What does this have to do with chemistry: matter and energy? Chemistry is how the world works, part I It occurs at a level we can t really see, but its effects can be very tangible The behavior of matter and energy is NOT dependent on worldview How you interpret this behavior IS How you act IS What is Energy then? The ability to do work, or cause a temperature change (heat transfer) Kinetic energy: energy of mass and motion. Temperature is a measure of KE of a molecule Potential energy: stored energy. Energy in chemical bonds for example Let s try and understand the basics Thermodynamics First Law: Energy in = Energy out Energy cannot be created or destroyed it just changes form Second Law: As energy changes form, some of it degrades Higher energy form to a lower one Law of conservation of matter: Matter is not created or destroyed, it just changes physically or chemically Trophic levels energy flow through ecosystems Autotrophs: primary producers Heterotrophs: consumers Primary, secondary, tertiary Decomposers Food webs depict complex relationships: omnivores? Many cross trophic levels Energy exchange in ecosystem Figure 2.11 Trophic levels Figure 2.14 2-10 2-12 3
Figure 54.5 An idealized pyramid of net productivity Trophic pyramid Figure 2.17 2-15 Energy pyramid/biomass period Figure 2.16 Matter quality (as a resource) What is matter? Atoms, molecules and compounds High quality matter is organized, concentrated and easy to access Low quality is dilute and disorganized 2-14 Law of conservation of matter Matter is recycled Matter is not created or destroyed, just changes form Sometimes the forms can change to be more or less toxic Some forms change more quickly due to chemical reactions Phases of matter: heat and pressure change states Solid: dense and organized. Gold ore vrs. Panning in a river Liquid: Atoms hit each other often, but less dense Gas: Atoms vibrate in their own space: even less dense 4
But water is different Solid: less dense! It floats Liquid: Gas: least dense Water doesn t behave like most substances Movement of atoms/ molecules Biological Chemistry Inorganic Molecules Organic Molecules: carbon - creating large, complex, diverse molecules Carbohydrates Lipids Proteins Nucleic Acids Inorganic molecules Organic compounds Sodium Chloride Water Nitrous oxide Ammonia Hydrogen sulfide No carbon 2-7 Organic molecules Figure 2.6 Chemical forms of matter Elements: building blocks Atoms: The smallest units Molecules: atoms as a single unit Compounds: Mixtures: compounds and elements: air 2-6 5
Molecules and compounds Figure 2.4 Elements and compounds 2-4 2-2 Matter: Elements and Atoms Matter is made of Elements An element is a substance that cannot be broken down. Elements are made up of atoms Protons (+) Neutrons (----) Electrons (-) smallest The nature of the atom determines its reactivity. Mercury (Hg) is an element It can combine with organic or inorganic molecules too Bacteria and chemical reactions can change mercury into methylmercury (toxic) [CH 3 Hg] + Fish can become toxic by eating smaller organisms that have absorbed it: biomagnification Law of conservation of matter and systems Elemental mercury (Hg) and [CH 3 Hg] + methylmercury Biomagnification Salt HgCl 2 Mercury in tons (1998) EPA (total 81 tons in 2002) e 6
Electrons occupy shells 8 in the outermost shell is ideal! How do they get there? Share. Matter: Atoms Protons and neutrons are in the center of an atom = nucleus Electrons move around the nucleus in orbitals (2 per) Orbitals are grouped in shells Movement of electrons between shells either requires or releases energy Atomic Structure Elements combine to form Compounds -Compound = NaCl Elements = Na and Cl Each element is made of one kind of atom which is different from every other Atoms are made of protons, electrons and neutrons Atomic numbers Orbitals and electron shells Atoms of the four elements most common in life Bonds and reactivity Bonds can form spontaneously to create stability in atoms Bonds can also form when molecules are dissociated, such as in water, or by some other chemical process, and the atoms come into contact with other atoms to which they bond. Some persistent environmental chemicals do this Or, bonds can be made by using an energy source (eg. Photosynthesis, and the synthesis of sugar Some molecules and compounds persist, and behave based on solubility and hydrophobic or hydrophilic tendencies 7
Energy exists in chemical bonds Energy can be harvested from chemical bonds (ATP) Energy rich molecules can be made using energy (photosynthesis and respiration) Molecules and Bonding Why do atoms bond together to form molecules? Ionic Bonding Ions donating electrons Covalent Bonds Sharing electrons Complex Molecules Polar and Non-polar Covalent Bonds Electronegativity Hydrogen bonds Molecules and Bonding Reactive elements can join together Ionic Bonds Ions donating electrons One becomes + One becomes These now attract each other and bond Molecules and Bonding Reactive elements can join together Ionic Bonds Donating electrons Covalent Bonds Sharing electrons Polar/non-polar Hydrogen bonds Polar bonds Polar and Non-polar bonds Polar and Non-polar Covalent Bonds Electronegativity Polar molecules can be weakly attracted to each other and form Hydrogen Bonds Hydrogen Bonds 8
Biological Significance of H-bonds: An environment for the chemistry of life. Solubility - polar molecules can dissolve into solution because of H-bond formation whereas non-polar molecules cannot Stability - Some polar molecules form H- bonds internally. These attractive forces serve to strengthen their internal structure. Water is special The Magic of Water 1. Cohesion and Adhesion Water is attracted to other water and to other polar substances by the charges in the structure. Hydrophilic = water loving. 2. Excellent biological solvent The Magic of Water 3. High heat capacity 4. High thermal conductivity 5. Less dense when frozen The water molecule is polar Some molecules and compounds persist, and behave based on solubility and hydrophobic or hydrophilic tendencies 9
Plastics PCBs and DDT are hydrophobic They do not dissolve in water Hydrophobic molecules tend to stick together PCBs Chemical reactions The making and breaking of chemical bonds - changing the composition of matter Some reactions progress to completion, but MOST are reversible Concentration of reactants can affect the rate of the reaction Chemical equilibrium Activation energy - some need it Catalysts - enhance or speed up the reaction Chemical Reactions Photosynthesis/Respiration 2H 2 + O 2 = 2H 2 0 Photosynthesis: Plants use carbon dioxide and produce starch and oxygen H 2 O + CO 2 = Starch/sugar + O 2 Respiration Animals use starch/ sugar and oxygen, and produce carbon dioxide Starch/sugar + O 2 = H 2 O + CO 2 How do we get to this energy? Cellular Respiration Aerobic (w/ oxygen) need for efficient transfer 6CO 2 + 6H 2 O + = C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + = C 6 H 12 O 6 + 6O 2 10
What you have learned so far Matter has mass, and is conserved, though can change It is comprised of atoms and molecules Energy can do work, and is also conserved, though can change state Energy is stored in chemical bonds Atoms have protons, neutrons and electrons. Electron arrangements are particularly important in determining reactivity. Ions (+ and -) are very reactive Bonding of atoms to others helps stabilize the atoms, and fill their electron shells this makes molecules What you have learned so far Some molecules are persistent in the environment, and can cause health concerns. They can also biomagnify. PCBs are an example. Some molecules are hydrophobic (water hating), some are hydrophilic (water loving). These characteristics can be very important. Chemical reactions move forward in a variety of ways: concentrations, activation energy, catalysts Water is a universal solvent and an excellent medium for chemical reactions, and has a high heat capacity. The water molecule is polar. Acids and bases Acids give up hydrogen ions (H + ) Bases readily bond with these H +. Remember ionic bonds Acids and bases are highly reactive For example H + breaks down CaCO 3 (calcium carbonate). Chemical Dissociation Salts, Acids, and Bases ph Buffers The physics and chemistry of adding acid to the ocean are well known. Gigatons of acid are lowering the ph of the worlds oceans, humans are totally responsible, and the more carbon dioxide we emit, the worse it s going to get Science, June 2010 Unprecedented in Earth s history 11
.1 Ph unit decline in acidity since industrialization (to the current 8.1). This represents a 30% increase in surface ocean acidity. It is lower now than in the past 20 million years, and its falling fast. Predicted to fall to 7.8 by the end of the century, an increase of 150%. What moves chemical reactions forward? High concentrations can drive chemical reactions, such as with acidification. Other things like heat energy, physical force etc. can also drive chemical reactions. Concentrations of solutions # of molecules in a specific volume Diffusion and Osmosis: Diffusion is the net movement of molecules from areas of high to low concentration Passive - requires no energy input Osmosis is the movement of water through a membrane that prevents solutes (large molecules) from passing. Net movement is from high to low concentrations Diffusion Hypertonic Hypotonic Isotonic Diffusion goes in all directions Osmosis- passive transport of water across a membrane 12
Knowledge (scientific) provides us with a basis from which to make decisions and take action. At what point do we have enough knowledge to make those decisions and take that action? Scientific process can move us forward but also be an excuse for inaction Know where your knowledge comes from 13