Transcript ch 2 power point

Science, Matter, Energy, and Systems
Chapter 2
Core Case Study: Carrying Out a
Controlled Scientific Experiment
 Problem: How does deforestation affect the loss
of water and soil nutrients?
 1963 - 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)
2-1 What Is Science?
 Concept 2-1 Scientists collect data and develop
theories, models, and laws about how nature
works.
Science Is a Search for Order
in Nature (1)
 Identify a problem
 Find out what is known about the problem
 Ask a question to be investigated (can only have
1 variable to be tested)
 Gather data
 Hypothesize
 Make testable predictions
 Keep testing and making observations
 Accept or reject the hypothesis
Scientific Method
 You want to design an experiment to determine
how soil pollution affects elderberry bushes.
1) chose 2 variables
• Independent (manipulated)
• Dependent (responding) – must be measurable
 concentration of salt vs # elderberries on each
bush
2) Write your hypothesis (needs a prediction for
both variables)
 Increased salt concentrations in soil result in a
decrease in the number of berries produced by
elderberry bushes.
Scientific Method
 In addition to your IV and DV, you must include
a control. A control is the exact duplicate of the
experiment with no manipulation of the IV.
An elderberry bush with no salt added
3) Collect and analyze data
Present in data tables and graphs (remember
graphing rules!)
4) Draw conclusions that are supported by the
data.
Science Is a Search for Order
in Nature (2)
 Important features of the scientific process
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Curiosity
Skepticism
Peer review
Reproducibility
Openness to new ideas
Easter Island – do we know
what really happened?
 Island is located in the S. Pacific, 2,200 miles (3,600 km)
off the coast of Chile
 Polynesians used canoes to colonize island and then
fish.
 Islanders thrived and the population increased
 Started cutting trees at an unsustainable rate
 Used trees for canoes, fires, erecting statues
 Once the large trees were gone, no canoes could be
made and no one could leave the island.
 With trees gone, spring and streams dried up, soil
eroded, crops failed and famine occurred.
 The islanders started to fight and the population
sharply decreased. By the late 1870s, only about
100 people remained.
Science Focus: Easter Island: Revisions
to a Popular Environmental Story
 New scientific data and reevaluation of old data can
revise hypotheses.
 Some revisions with the Easter Island tragedy
• Polynesians arrived about 800 years ago, not
2,900 years ago
• Population may have reached 3000, not 15,000
• Determined that the trees were used in an
unsustainable manner, but rats may have
multiplied and eaten the seeds of the trees
• Population may have also declined due to contact
with visitors/invaders and many were taken to be
sold as slaves.
Scientists Use Reasoning, Imagination,
and Creativity to Learn How Nature Works
 Important scientific tools
• Inductive reasoning- using specific
observations to form general conclusions
• Deductive reasoning – using general
observations to form specific conclusions.
 Scientists also use
• Intuition
• Imagination
• Creativity
Scientific Theories and Laws Are the
Most Important Results of Science
 Scientific theory
• Widely tested
• Supported by extensive evidence
• Accepted by most scientists in a particular area
 Scientific law, law of nature – no exceptions
 Paradigm shift – a change in thinking when a
majority of scientists accept a new framework for
theories and laws.
Environmental Science Has Some
Limitations
 Particular hypotheses, theories, or laws have a
high probability of being true while not being
absolute
 Bias can be minimized by scientists
 Statistical methods may be used to estimate
very large or very small numbers
 Environmental phenomena involve interacting
variables and complex interactions
 Scientific process is limited to the natural world
Science Focus: Statistics and Probability
 Statistics
• Collect, organize, and interpret numerical data
 Probability
• The chance that something will happen or be
valid
2-2 What Is Matter?
 Concept 2-2 Matter consists of elements and
compounds, which are in turn made up of atoms,
ions, or molecules.
Matter Consists of Elements and
Compounds
 Matter
• Has mass and takes up space
 Elements
• Unique properties
• Cannot be broken down chemically into other
substances
 Compounds
• Two or more different elements bonded together
in fixed proportions
Atoms, Ions, and Molecules Are the
Building Blocks of Matter (1)
 Atomic theory – all elements are made of atoms
 Subatomic particles
• Protons (p) with positive charge and neutrons (0) with
no charge in nucleus
 Negatively charged electrons (e) orbit the nucleus
 Atomic number – number of protons in an atom
 Mass number
• Protons plus neutrons
EX: Oxygen has 8 p, 8 n and 8 e- What is the mass?
Atoms, Ions, and Molecules Are the
Building Blocks of Matter (2)
 Isotopes – when a particular atom has different
numbers of neutrons and therefore different
masses Ex: C-12, C-13, C-14
 Ions – have electrical charges
• Gain or lose electrons
• Form ionic compounds
Ex: NaCl, Li2S
 pH
• Measure of acidity
• H+ and OH-
pH Scale
Atoms, Ions, and Molecules Are the
Building Blocks of Matter (3)
 Molecule
• Two or more atoms of the same or different
elements held together by chemical bonds
Ex: H20, CO, O3
 Chemical formula
Organic Compounds Are the
Chemicals of Life
 Inorganic compounds- contain 1 atom of C or
no atoms of C (except methane CH4)
 Organic compounds
• Hydrocarbons and chlorinated hydrocarbons
• Simple carbohydrates
• Macromolecules: complex organic molecules
• Complex carbohydrates
• Proteins (formed from amino acids)
• Nucleic acids (DNA, RNA – formed from
nucleotides)
• Lipids
Matter Comes to Life through Genes,
Chromosomes, and Cells
 Cells: fundamental units of life
 Genes: sequences of
nucleotides within the DNA
 Chromosomes: composed
of many genes
Matter Occurs in Various Physical Forms
 Solid
 Liquid
 Gas
Some Forms of Matter Are More
Useful than Others
 Matter quality is a measure of the usefulness of
matter as a resource based on its availability
and concentration
 High-quality matter- is highly concentrated,
found near the earth’s surface and has the
potential to be used as a resource. Ex: coal,
aluminum can, salt
 Low-quality matter- coal fired power plant
emissions, aluminum ore, salt water solution
2-3 How Can Matter Change?
 Concept 2-3 When matter undergoes a
physical or chemical change, no atoms are
created or destroyed (the law of conservation of
matter).
Matter Undergoes Physical, Chemical,
and Nuclear Changes
 Physical change – no new substance is
formed
 Chemical change, chemical reaction- atoms
or ions rearrange C + O2 → CO2
 Nuclear change
• Natural radioactive decay
• Radioisotopes: unstable U-235
• Types of radiation are alpha, beta and gamma
• Nuclear fission - splitting apart of the nucleus
• Nuclear fusion – light elements fuse to make
heavier elements. Ex: the sun
We Cannot Create or Destroy Matter
 Law of conservation of matter
 Matter consumption
• Matter is converted from one form to another
• So, can we ever really throw something away?
2-4 What is Energy and How Can It
Be Changed?
 Concept 2-4A When energy is converted from
one form to another in a physical or chemical
change, no energy is created or destroyed
(first law of thermodynamics).
 Concept 2-4B Whenever energy is changed
from one form to another, we end up with lowerquality or less usable energy than we started
with (second law of thermodynamics).
Energy Comes in Many Forms
 Energy- the capacity to do work or transfer heat. Work is
done when something is moved. W= fd
 Kinetic energy
• Heat – heat flows from the warmer object to the
cooler
• Transferred by radiation, conduction (when objects
are in contact), or convection (movement of heat
within liquids and gases)
• Electromagnetic
radiation – energy
travels in waves
Potential energy - Stored energy
Ex: unlit match, gasoline in a tank, food in your pantry.
Potential energy can change into kinetic. Ex: burning the
gasoline.
The PE is stored in the bonds.
Energy can be mechanical, chemical, electrical, thermal…
Some Types of Energy Are More
Useful Than Others
 High-quality energy – concentrated energy with
a high capacity to do useful work. Ex: nuclear
fission, burning gasoline
 Low-quality energy – energy is dispersed and
has little capacity to do work. Ex: low
temperatures
Energy Changes Are Governed by Two
Scientific Laws
 First Law of Thermodynamics (law of the
conservation of energy)
• Energy cannot be created or destroyed
• 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
• In all energy conversions, some waste heat is
always produced
Energy efficiency or productivity
 Ex: Only 6% of the energy from burning gasoline
goes into moving the car. The other 94% is
released as heat.
 Ex: Only 5% of energy used in
incandescent lights goes into
producing light. The other 95%
is released as heat. The energy
that becomes light in a CFL is 20%.
 Ex: During each step of the food chain, only 10%
of the energy is transferred to the next.
2-5 What Are Systems and How Do They
Respond to Change?
 One approach to ES is to consider earth to be made
of many environmental systems. Each part of the
system works together to perform a function or set
of functions. By considering each system
individually, the impact humans have on the
environment can by simplified.
 Open system- systems that exchange energy and
matter across their boundaries.
 Closed system- systems that exchange energy but
not matter across their boundaries. EX: water cycle
 Concept 2-5A Systems have inputs, flows, and
outputs of matter and energy, and their behavior
can be affected by feedback.
 Concept 2-5B Life, human systems, and the
earth’s life support systems must conform to the
law of conservation of matter and the two laws of
thermodynamics.
Systems Have Inputs, Flows,
and Outputs
 System
• Inputs from the environment
• Flows, throughputs
• Outputs
Systems Respond to Change through
Feedback Loops
 Positive feedback loop system continues in the
same direction Ex: melting of polar ice amplifies
the melting
 Negative, or corrective, feedback loop –
system changes direction from which it is
moving Ex: The more aluminum is recycled, the
less aluminum needs to be mined
Is the example below a positive or
negative feedback loop?
 You perspire on a hot day.
 This is a negative feedback loop.
 You perspire because your skin gets hot.
Perspiration evaporates from the surface of your
skin and your skin surface temperature
decreases. Evaporation is a cooling process!
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
 Tipping point, threshold level
• Causes a shift in the behavior of a system
System Effects Can Be Amplified
through Synergy
 Synergistic interaction, synergy
(when the combined effect is greater than the
sum of the separate effects)
• Helpful Ex: getting a group of people to write
letters
• Harmful Ex: Smoking (10x more likely to get
lung cancer) and inhaling asbestos particles 5x
more likely to get cancer) But exposure to both
increases the likelihood by 50x!
Human Activities Can Have Unintended
Harmful Results
 Deforested areas turning to desert
 Coral reefs dying
 Glaciers melting
 Sea levels rising