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Science, Matter, Energy, and Systems Chapter 2 – Part 1 Scientific Process
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Core Case Study: Carrying Out a Controlled Scientific Experiment F. Herbert Bormann, Gene Likens, et al.: Hubbard Brook Experimental Forest in NH (U.S.) Compared the loss of water and nutrients from an uncut forest (control site) with one that had been stripped (experimental site)
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The Effects of Deforestation on the Loss of Water and Soil Nutrients Built v-shaped dams across the creeks at the bottom of forested valleys Measured amounts of water and dissolved plant nutrients
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The Effects of Deforestation on the Loss of Water and Soil Nutrients Investigators cut down all trees and shrubs in one valley Sprayed area with herbicides to prevent regrowth
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The Effects of Deforestation on the Loss of Water and Soil Nutrients Amount of water flowing out of the deforested valley increased by 30-40% Eroded soil Removed 6x more nutrients from soil Conclusions????
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Scientists Use Reasoning, Imagination, and Creativity to Learn How Nature Works Important scientific tools Inductive reasoning – involves using specific observations and measurements Specific General Deductive reasoning – involves using logic to arrive at a specific conclusion based on a generalization or premise General Specific
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Inductive or Deductive? All birds have feathers. Eagles are birds. Eagles have feathers. A meatball falls to the ground when dropped from a height of 10 feet. An olive falls to the ground when dropped from a height of 2 feet. All objects fall to the Earth’s surface when dropped.
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Nature of Science An organized way of using evidence to learn about the natural world Observations Hypothesis Experiment Results Conclusion Repeating Peer Review
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Nature of Science Hypothesis Proposed scientific explanation for a set of observations A good hypothesis must: 1.Be testable. 2.Be a statement, not a question. 3. Predict cause and effect. If… then…
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Nature of Science Null Hypothesis: States that the variable will have no effect on the outcome of the experiment Example: Light intensity has no effect on plant growth. Allows conclusions to be drawn that “reject” or “fail to reject” the null hypothesis If… then…
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Able to Change Variable Every experiment measures two Independent variable -- the variable that the experimenter controls. answers the question "What do I change/control?" Dependent variable -- the variable the experimenter measures (results). answers the question "What do I observe/measure?"
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Scenario A group of students is assigned a populations project in their APES class. They decide to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.
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Independent Variable – What do I control ? A group of students is assigned a populations project in their APES class. They decided to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.
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Dependent Variable – What do I measure? A group of students is assigned a populations project in their APES class. They decided to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.
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Controlled Experiment Experimental group - group that receives treatment in a controlled experiment. Contains Independent Variable Control group - group that does not receive treatment in a controlled experiment. Does not contain Independent Variable
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Experimental Group– Which group has the IV? A group of students is assigned a populations project in their APES class. They decided to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.
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Control – Which group doesn’t have the IV? A group of students is assigned a populations project in their APES class. They decided to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.
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Able to Change Variable Levels – measure of your independent variable Example: Number of seeds in a pot Number of fish in a fish bowl Number of times that an action is repeated
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Levels – how is the IV measured? A group of students is assigned a populations project in their APES class. They decided to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.
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Controlled Experiment Constant What remains constant between experimental groups Trials Number of times you repeat an experiment More tries = more reliable results Sample size The number of objects or events studied
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Constants – What do I keep the same? A group of students is assigned a populations project in their APES class. They decided to determine the effect of sunlight on radish plant height. They set up 3 clay pots, each one containing 12 radish plants, 100g of potting soil, and given 25 mL of water daily. The pots are all 4 inches in diameter. One pot is placed in 24 hours darkness, one in 12 hours sunlight/12 hours darkness, and the last in 24 hours sunlight. After 5 days, they measure the height of all the plants in each pot.
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Not all experiments are created equal… Frontier science – preliminary testing Reliable science – well supported and studied experiments High probability of being true Unreliable – unsupported via peer review Critical Thinking Questions: Was the experiment controlled? Have the data been verified? Have the results been reproduced by other scientists? Are the investigators unbiased? Have the conclusions been verified by impartial peer review? Critical Thinking Questions: Was the experiment controlled? Have the data been verified? Have the results been reproduced by other scientists? Are the investigators unbiased? Have the conclusions been verified by impartial peer review?
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Scientific Theories and Laws Theory Verified, credible and widely accepted hypothesis Make future predictions Law Mathematical description of what a theory explains Paradigm Shift Majority of scientists in a field accept a new framework for theories and laws
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Your Turn! Case of the Ivory Billed Woodpecker http://www.pbs.org/wgbh/nova/nature/ivory-billed- woodpecker.html http://www.pbs.org/wgbh/nova/nature/ivory-billed- woodpecker.html
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The Case of the Ivory Billed Woodpecker Case of the Ivory Billed Woodpecker http://www.pbs.org/wgbh/nova/nature/ivory-billed- woodpecker.html http://www.pbs.org/wgbh/nova/nature/ivory-billed- woodpecker.html
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The Case of the Ivory Billed Woodpecker
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Wisconsin Fast Plants Laboratory Project 1.Make a list of questions you have about plants. Be creative! 2.Suggested IV: Fertilizer Crowding Acid (vinegar) Soil Glucose
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Your Turn: Wisconsin Fast Plant Project! 1.On your paper include the following information: 1.Question 2.Hypothesis 3.Null Hypothesis 4.Experimental Design 1.Independent and Dependent Variable 2.Control and Experimental Groups 3.Levels 4.Constants 5.Sample Size 5.Detailed Procedure
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Peer Review Is the hypothesis testable, a statement, and does it predict a cause and effect relationship? Will the data be quantitative rather than qualitative? Are there any unaccounted for variables? If so, what are they? Is the procedure logical? Any remaining questions or comments?
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Science, Matter, Energy, and Systems Chapter 2 – Part 2 Chemical Bonding
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Matter Any substance that: Occupies space Has mass Is made of atoms
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Some Forms of Matter Are More Useful than Others Matter quality – measure of how useful a form of matter is to humans as a resource Based on availability and concentration
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Some Forms of Matter Are More Useful than Others High-quality matter highly concentrated Near the Earth’s surface Great potential as a resource Low-quality matter Not highly concentrated Located deep underground or ocean Little potential for use
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We Cannot Create or Destroy Matter Matter consumption Matter is converted from one form to another Law of conservation of matter – matter cannot be created nor destroyed Everything we think we have thrown away remains here with us in some form…
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Matter Consists of Elements and Compounds Elements Unique properties Cannot be broken down chemically into other substances SPONCH Compounds Two or more different elements bonded together in fixed proportions
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Organic Compounds Are the Chemicals of Life Inorganic compounds Organic compounds Macromolecules: complex organic molecules Carbohydrates Proteins Nucleic acids Lipids
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Atomic Composition No unique substances in living things, just different amounts “Same ingredients, different recipes.”
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Example: Carbon Atomic Number = 6 6 Protons 6 Electrons Atomic Mass = 12 12 – 6 = 6 6 Neutrons
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Your Turn! Atomic Mass #...
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ELECTRONEGATIVITY The tendency of an atom to attract electrons to itself when it is bonded to another atom
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Increase
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BONDING OPTIONS COVALENT BOND By sharing electrons (small difference in EN) IONIC BOND By transferring electrons (producing ions) (big difference in EN)
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Chemical Bonding Atoms combine according to certain rules Rules determined by the number of electrons found in the outermost energy level First energy level = 2 electrons Second energy level = 8 electrons Third energy level = 8 electrons
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Chemical Bonding
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Covalent Bonds Sharing of electrons Electrons travel in the orbitals of both atoms Each atom fills out the outermost energy level
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Water: A Covalent Bond
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Ionic Bonds Transfer of electrons Ex. NaCl Sodium has one electron in outer shell Na + Chlorine has seven electrons in its outer shell Cl –
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Ionic Bond Ion = charged particle Anion = negatively charged Cation = positively charged Strong attraction between oppositely charged ions forms the ionic bond
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Ionic Bond
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Trick to Remember! If an atom GAINS electrons, its overall charge becomes more negative. If it LOSES electrons, its charge becomes more positive
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Your Turn! Bonding Practice Covalent: Carbon and Chlorine Ionic: Sodium and Chlorine
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Science, Matter, Energy, and Systems Chapter 2 – Part 3 Water
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Why is it important? Covers ¾ of Earth’s surface! Most abundant compound in most living things Exceptional substance with many extraordinary qualities!
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Unusual Properties Determine characteristics of: Atmosphere Ocean Land
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Water’s Structure…Simple? Hydrogen 1 electron…needs 2 Oxygen 6 electrons (outer shell)…needs 8 Covalent Bonding
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Polar Molecule Charges are unevenly distributed Partial positive Partial negative Electronegativites of atoms differ
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Electronegativity
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Hydrogen Bonds Attraction between two different molecules “weak” bond Not “real” bond b/c no sharing or transferring of electrons Ex: water, proteins, & DNA
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How many hydrogen bonds can each water molecule form?
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As one hydrogen bond is broken another one forms Each bond lasts trillionths of a second Substantial percentage bonded to neighbor
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Cohesion Attraction between molecules of the same substance Causes molecules on the surface of water to be drawn inward Why water forms beads on smooth surfaces Why insects can walk on water
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Surface Tension Result of cohesion How it “stretches or resists breaking” Water molecules form weak elastic membrane Water to water Water to air
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Adhesion Attraction between molecules of different substances Meniscus Water to WaterWater to Glass
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Capillary Action Forces that draw water out of the roots of a plant and up into its stems and leaves Holds column of water together as it rises Cohesion and adhesion
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Density Less dense as a solid Hydrogen bonds stay connected less energy in system so bonds don’t break More space occurs between water molecules
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Solutions All components are evenly distributed throughout Solute – substance that is dissolved Solvent – the substance in which the solute dissolves Due to water’s polarity Can dissolve ionic compounds and other polar molecules
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Solubility Water surrounds the charged ends and separates the molecules
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Suspensions Mixtures of water and nondissolved material Materials don’t dissolve but separate into pieces so small that they do not settle out Example Blood
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Your Turn! Water Property Lab
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Science, Matter, Energy, and Systems Chapter 2 – Part 4 Isotopes and Nuclear Reactions
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Isotopes Number of neutrons can vary from one atom of an element to another Changes atomic mass, not atomic number Atomic number NEVER changes
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Isotopes H = hydrogen 1 1 H = deuterium H = tritium 1 2 1 3 Identified by mass #
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Isotopes Isotopes have SAME number of protons but DIFFERENT numbers of neutrons Heavier Behave identical in chemical reactions Same # electrons = same chemical properties
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Radioactive Isotopes Diagnose and treat diseases Cardiovascular disease Cancer radiation Sterilize foods Kill bacteria Preserve food Measure the ages of certain rocks Fossils
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Matter Undergoes Physical, Chemical, and Nuclear Changes Nuclear change – changes in the nuclei of atoms Nuclear fission – nucleus splits and releases neutrons plus energy
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Matter Undergoes Physical, Chemical, and Nuclear Changes Nuclear change – changes in the nuclei of atoms Nuclear fission – nucleus splits and releases neutrons plus energy Nuclear fusion – two nuclei fuse together and release energy
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Nuclear Power 6:51
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Light-Water-Moderated and -Cooled Nuclear Power Plant with Water Reactor
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After 3 or 4 Years in a Reactor, Spent Fuel Rods Are Removed and Stored in Water
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Science, Matter, Energy, and Systems Chapter 2 – Part 5 pH
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What do vinegar, lemons, and orange juice have in common?
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Characteristics of Acids Taste Sour React with metals Often produce hydrogen gas Can burn your skin
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What do milk, Comet, and Tums have in common?
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Characteristics of Bases Taste Bitter Feel Slippery Neutralize Acids Antacids Dissolve grease
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But, what exactly are acids and bases?
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Substance that ionizes in water to give hydrogen ions (H + ) Acid
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Examples of Acids HCl H 2 SO 4 HNO 3 HF Juices
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Substance that ionizes in water to give hydroxide ions (OH - ) Base
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Examples of Bases NaOH Ca(OH) 2 KOH Soap, Ammonia, Baking Soda
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The pH Scale Measurement system that indicates the concentration of H + ions in solution. The pH scale ranges from 0 to 14.
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The pH Scale pH = “power of hydrogen” Each step increases by a power of ten
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pH Scale
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pH Calculations Remember: For every one-increment change in pH, the ions change by a factor of 10. Example: What is the difference in H+ concentration between pH 6 and pH 4? pH 6 – pH 4 = pH 2 H+ is 100 times more concentrated in the pH 4 solution
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pH Calculations Remember: Concentration of H+ and OH- always equals 10 -14 M or pH 14 Example: [H+] = 10 -6 M pH is 6: weak acid [OH-] = 10 -8 M
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pH and Water WWhy does water have a pH of 7? Hydronium ions = hydroxide ions (H + ) = (OH - ) H 2 0H + + OH -
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Interesting fact… Water can act as an acid or a base!!!
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Interesting fact… Amphoteric - substance that can act as either an acid or a base.
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Your Turn! Review of pH Calculations
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pH Scale
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Your Turn…pH of natural substances Substances: Soil Freshwater Saltwater Rainwater Tools: Soil – capsules Water (use 2 of the following) - pH meter, litmus paper, or microkit
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Your Turn…pH of natural substances CapsulespH MeterLitmus Paper Microkit Soil Freshwater Saltwater Rainwater
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Buffers Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH.
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Buffers are working while you exercise!
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Ocean pH Surface water pH ranges from 8.0 to 8.3 Average 8.1 Ocean water combines with CO 2 Forms weak Carbonic Acid H 2 0 + CO 2 H 2 CO 3 H + + HCO 3 -
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Ocean pH AAverage pH 8.1 BASIC? CCarbonic Acid? Why is the ocean pH slightly basic when CO 2 (an acid ) is added?
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Carbonate Buffering Keeps ocean pH about same (8.1) pH too high, carbonic acid releases H+ pH too low, bicarbonate combines with H+ H 2 CO 3 H + + HCO 3 - HCO 3 - + H + H 2 CO 3
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Carbonate Buffering Marine organisms die and sink into deep ocean Calcium carbonate in shell neutralizes acid through buffering CaCO 3 CO 3 - + H + HCO 3 - + H + H 2 CO 3
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Carbonate Buffering Dead mollusks are the antacids of the sea!
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Carbonate buffering
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Recent Decrease in Ocean Acidity Excess carbon dioxide in atmosphere 33% CO 2 released by burning fossil fuels ends up in ocean Overwhelming oceans natural ability to buffer itself pH has decreased 0.1 since preindustrial times
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Recent Decrease in Ocean Acidity More difficult for certain marine creatures to build hard parts out of calcium carbonate Plankton Corals Alter food chain of ocean!
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Science, Matter, Energy, and Systems Chapter 2 – Part 6 Thermodynamics
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Energy Comes in Many Forms Kinetic energy - energy of motion Mass and velocity! Electromagnetic radiation of waves Short = greater energy
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Kinetic energy Atoms and molecules in any gas, liquid, or solid are always in motion Vibrate around average position Kinetic Energy = ½ (mass)(velocity) 2
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Temperature Measure of the average kinetic energy of the atoms and molecules in the substance Measured in degrees Celsius Fahrenheit Kelvin
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Heat Measure of total kinetic energy of the atoms and molecules in a substance Measured in calories
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Calorie Amount of heat needed to raise the temperature of 1g of water by 1 o C 1 food Calorie (1 kilocalorie) = 1000 calories
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What’s the difference? Which has greater average Kinetic Energy? Higher Temperature? Which has greater total Kinetic Energy? More Heat?
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Energy Comes in Many Forms Potential energy - energy of position Stored energy; can be changed into kinetic energy Examples: rock held in hand, unlit match, gasoline
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Some Types of Energy Are More Useful Than Others Energy quality - measure of an energy source’s capacity to do useful work High-quality energy – concentrated energy that has a high capacity to do useful work High-temperature heat Concentrated sunlight High velocity wind
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Some Types of Energy Are More Useful Than Others Energy quality - measure of an energy source’s capacity to do useful work Low-quality energy – energy that is dispersed and has little capacity to do useful work Low temperatures
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Energy Changes Are Governed by Two Scientific Laws First Law of Thermodynamics Energy input always equals energy output Second Law of Thermodynamics Energy always goes from a more useful to a less useful form when it changes from one form to another Decreased energy efficiency
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Life application 94% of the money you spend for gasoline is not used to transport you anywhere!
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The Second Law of Thermodynamics in Living Systems
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Your Turn! Potential vs. Kinetic worksheet
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Science, Matter, Energy, and Systems Chapter 2 – Part 7 Systems
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Systems Have Inputs, Flows, and Outputs System – set of components that function and interact in some regular way Inputs from the environment Flows, throughputs Outputs
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Systems Respond to Change through Feedback Loops Positive feedback loop - causes a system to change in the same direction
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Systems Respond to Change through Feedback Loops Negative feedback loop – causes a system to change in the opposite direction from which it is moving Opposing process Can promote sustainability! Aluminum mining can recycling
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Video Clip – Planet Earth Forests Cicada Life Cycle 21:00-26:00
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Time Delays Can Allow a System to Reach a Tipping Point Time delays vary Between the input of a feedback stimulus and the response to it Example: Planting trees Tipping point, threshold level Causes a shift in the behavior of a system
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System Effects Can Be Amplified through Synergy Synergistic interaction – two or more processes interact so that the combine effect is greater than the sum of their separate effects Helpful E.g., campaign vs. individual persuasion Harmful E.g., Smoking and inhaling asbestos particles
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