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Science, Matter, Energy, and Systems
Chapter 2 – Part 1Scientific Process
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)
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
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
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????
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
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.
Deductive
Inductive
Nature of Science
An organized way of using evidence to learn about the natural world• Observations• Hypothesis• Experiment• Results• Conclusion• Repeating • Peer Review
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…
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…
Able toChange
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?"
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.
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.
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.
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
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.
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.
Able toChange
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
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.
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
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.
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?
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
Your Turn!
Case of the Ivory Billed Woodpecker http://www.pbs.org/wgbh/nova/nature/ivor
y-billed-woodpecker.html
The Case of the Ivory Billed Woodpecker
Case of the Ivory Billed Woodpecker http://www.pbs.org/wgbh/nova/nature/ivor
y-billed-woodpecker.html
The Case of the Ivory Billed Woodpecker
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
Your Turn: Wisconsin Fast Plant Project!
1. On your paper include the following information:
1. Question 2. Hypothesis3. Null Hypothesis4. Experimental Design
1. Independent and Dependent Variable2. Control and Experimental Groups3. Levels4. Constants5. Sample Size
5. Detailed Procedure
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?
Science, Matter, Energy, and Systems
Chapter 2 – Part 2Chemical Bonding
MatterAny substance that: Occupies space Has mass Is made of atoms
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
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
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 destroyedEverything we think we have thrown away remains
here with us in some form…
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
Organic Compounds Are the Chemicals of Life
Inorganic compounds
Organic compounds• Macromolecules: complex organic
molecules• Carbohydrates• Proteins• Nucleic acids• Lipids
Atomic Composition
No unique substances in living things, just different amounts
“Same ingredients, different recipes.”
Example: Carbon
• Atomic Number = 6• 6 Protons• 6 Electrons
• Atomic Mass = 12• 12 – 6 = 6• 6 Neutrons
Your Turn!
Atomic Mass #...
ELECTRONEGATIVITY The tendency of an atom to attract
electrons to itself when it is bonded to another atom
BONDING OPTIONSCOVALENT BOND By sharing electrons
(small difference in EN)
IONIC BOND By transferring electrons (producing ions)
(big difference in EN)
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
Chemical Bonding
Covalent Bonds
Sharing of electrons• Electrons travel in
the orbitals of both atoms
Each atom fills out the outermost energy level
Water: A Covalent Bond
Ionic Bonds
Transfer of electrons
Ex. NaCl• Sodium has one
electron in outer shell Na +
• Chlorine has seven electrons in its outer shell Cl –
Ionic Bond
Ion = charged particle• Anion = negatively charged• Cation = positively charged
Strong attraction between oppositely charged ions forms the ionic bond
Ionic Bond
Trick to Remember! If an atom GAINS electrons,
its overall charge becomes more negative.
If it LOSES electrons, its charge becomes more positive
Your Turn!
Bonding Practice Covalent: Carbon and Chlorine Ionic: Sodium and Chlorine
Science, Matter, Energy, and Systems
Chapter 2 – Part 3Water
Why is it important?
Covers ¾ of Earth’s surface!• Most abundant compound in most
living things Exceptional substance with many
extraordinary qualities!
Unusual Properties Determine characteristics of:
Atmosphere
Ocean
Land
Water’s Structure…Simple?
Hydrogen• 1 electron…needs 2
Oxygen• 6 electrons (outer
shell)…needs 8 Covalent Bonding
Polar Molecule
Charges are unevenly distributed• Partial positive• Partial negative
Electronegativites of atoms differ
Electronegativity
Electronegativity
Hydrogen Bonds
Attraction between two different molecules
“weak” bond Not “real” bond b/c
no sharing or transferring of electrons • Ex: water, proteins, &
DNA
How many hydrogen bonds can each water molecule form?
As one hydrogen bond is broken another one forms
Each bond lasts trillionths of a second
Substantial percentage bonded to neighbor
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
Surface Tension
Result of cohesion How it “stretches or
resists breaking” Water molecules form
weak elastic membrane• Water to water • Water to air
Adhesion
Attraction between molecules of different substances• Meniscus
Water to Water
Water to Glass
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
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
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
Solubility
Water surrounds the charged ends and separates the molecules
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
Your Turn!
Water Property Lab
Science, Matter, Energy, and Systems
Chapter 2 – Part 4Isotopes and Nuclear
Reactions
Isotopes
Number of neutrons can vary from one atom of an element to another• Changes atomic mass, not atomic
number Atomic number NEVER changes
Isotopes
H = hydrogen1
1
H = deuterium
H = tritium
1
2
1
3
Identified by mass #
Isotopes
Isotopes have SAME number of protons but DIFFERENT numbers of neutrons• Heavier• Behave identical in chemical reactions
Same # electrons = same chemical properties
Radioactive Isotopes
Diagnose and treat diseases• Cardiovascular
disease• Cancer radiation
Sterilize foods• Kill bacteria • Preserve food
Measure the ages of certain rocks• Fossils
Matter Undergoes Physical, Chemical, and Nuclear Changes
Nuclear change – changes in the nuclei of atoms• Nuclear fission –
nucleus splits and releases neutrons plus energy
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
Nuclear Power 6:51
Light-Water-Moderated and -Cooled Nuclear Power Plant with Water Reactor
After 3 or 4 Years in a Reactor, Spent Fuel Rods Are Removed and Stored in Water
Science, Matter, Energy, and Systems
Chapter 2 – Part 5pH
What do vinegar, lemons, and orange juice have in common?
Characteristics of Acids
Taste Sour React with metals Often produce
hydrogen gas Can burn your skin
What do milk, Comet, and Tums have in common?
Characteristics of Bases
Taste Bitter Feel Slippery Neutralize Acids• Antacids
Dissolve grease
But, what exactly are acids and
bases?
Substance that ionizes in water to give hydrogen ions (H+)
Acid
Examples of Acids HCl H2SO4
HNO3 HF Juices
Substance that ionizes in water to give hydroxide ions (OH-)
Base
Examples of Bases
NaOH Ca(OH)2 KOH Soap, Ammonia,
Baking Soda
The pH Scale
Measurement system that indicates the concentration of H+ ions in solution.• The pH scale ranges from 0 to
14.
The pH Scale
pH = “power of hydrogen”• Each step increases by a power
of ten
pH Scale
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
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
pH and Water
Why does water have a pH of 7?• Hydronium ions = hydroxide ions • (H+) = (OH-)
H20 H+ + OH-
Interesting fact…
Water can act as an acid or a base!!!
Interesting fact…
Amphoteric -substance that can act as either an acid or a base.
Your Turn!
Review of pH Calculations
pH Scale
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
Your Turn…pH of natural substances
Capsules
pH Meter Litmus Paper
Microkit
Soil
Freshwater
Saltwater
Rainwater
Buffers
Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH.
Buffers are working
while you exercise!
Ocean pH Surface water pH ranges from 8.0 to 8.3• Average 8.1
Ocean water combines with CO2 Forms weak Carbonic Acid
H20 + CO2 H2CO3 H+ + HCO3-
Ocean pH
Average pH 8.1• BASIC?
Carbonic Acid?
Why is the ocean pH slightly basic when CO2 (an acid) is
added?
Carbonate Buffering
Keeps ocean pH about same (8.1) pH too high, carbonic acid releases H+
pH too low, bicarbonate combines with H+H2CO3 H+ + HCO3
-
HCO3- + H+ H2CO3
Carbonate Buffering
Marine organisms die and sink into deep ocean• Calcium carbonate in shell neutralizes acid
through buffering
CaCO3 CO3- + H+
HCO3- + H+ H2CO3
Carbonate Buffering
Dead mollusks are the antacids of the sea!
Carbonate buffering
Recent Decrease in Ocean Acidity
Excess carbon dioxide in atmosphere• 33% CO2 released by burning fossil fuels
ends up in ocean Overwhelming oceans natural ability to
buffer itself• pH has decreased 0.1 since preindustrial
times
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!
Science, Matter, Energy, and Systems
Chapter 2 – Part 6Thermodynamics
Energy Comes in Many Forms
Kinetic energy - energy of motion• Mass and velocity!• Electromagnetic
radiation of waves• Short = greater
energy
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
Temperature
Measure of the average kinetic energy of the atoms and molecules in the substance
Measured in degrees• Celsius• Fahrenheit• Kelvin
Heat
Measure of total kinetic energy of the atoms and molecules in a substance
Measured in calories
Calorie
Amount of heat needed to raise the temperature of 1g of water by 1oC
1 food Calorie (1 kilocalorie) = 1000 calories
What’s the difference?
Which has greater average Kinetic Energy?• Higher Temperature?
Which has greater total Kinetic Energy?• More Heat?
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
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
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
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
Life application
94% of the money you spend for gasoline is not used to transport you anywhere!
The Second Law of Thermodynamics in Living Systems
Your Turn!
Potential vs. Kinetic worksheet
Science, Matter, Energy, and Systems
Chapter 2 – Part 7Systems
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
Systems Respond to Change through Feedback Loops
Positive feedback loop - causes a system to change in the same direction
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
Video Clip – Planet Earth Forests
Cicada Life Cycle
21:00-26:00
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
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