Download Science, Matter, Energy, and Systems

Science, Matter, Energy, and
Systems
Chapter 2
Figure 2.1Controlled field experiment to measure the effects of deforestation on the loss
of water and soil nutrients from a forest. V–notched dams were built into the
impenetrable bedrock at the bottoms of several forested valleys (left) so that all water
and nutrients flowing from each valley could be collected and measured for volume and
mineral content. These measurements were recorded for the forested valley (left), which
acted as the control site. Then all the trees in another valley (the experimental site) were
cut (right) and the flows of water and soil nutrients from this experimental valley were
measured for 3 years.
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)
⦿ Deforested area: 30-40% increase in water
flowing out of forest, eroded soil, and lost 6
to 8 times more nutrients
2-1 What Is Science?
⦿ Concept
2-1 Scientists collect data and
develop theories, models, and laws about how
nature works.
– endeavor to discover how nature
works and to use that knowledge to make
predictions about what is likely to happen in
nature.
⦿ Science
• Based on the assumption that events in the natural
world follow orderly cause-and-effect patterns that can
be understood through careful observation,
measurements, experimentation, and modeling.
Science Is a Search for Order
in Nature (1)
Figure 2.2
What scientists do. The essence of
science is this process for testing ideas
about how nature works. Scientists do not
necessarily follow the exact order of
steps shown here. For example,
sometimes a scientist might start by
formulating a hypothesis to answer the
initial question and then run experiments
to test the hypothesis.
Science Is a Search for Order
in Nature (2)
⦿ Some
terms
• Data – information needed to answer a question;
collected with senses or extensions of the senses.
• Experiments – procedures carried out under
controlled conditions to gather information and test
ideas.
• Scientific hypothesis – a possible and testable
explanation of what is observed in nature or in the
results of their experiments.
• Model – an approximate representation or simulation
of a system being studied.
• Scientific theory – well-tested hypothesis or group of
hypotheses; and explanation that has broad predictive
Science Is a Search for Order
in Nature (3)
⦿ Important
features of the scientific process
• Curiosity
• Skepticism
• Peer review
• Reproducibility
• Openness to new ideas
Science Focus: Easter Island: Revisions to
a Popular Environmental Story
⦿ Original
•
•
•
thoughts:
Polynesians arrived 2,900 years ago
Populations up to 15,000
Only 100 native islanders left by 1870’s because of
overuse of trees and supplies
⦿ Some
revisions in a popular environmental
story
• Polynesians arrived about 800 years ago
• Population may have reached 3000
• Used trees in an unsustainable manner, but rats
may have multiplied and eaten the seeds of the
trees
Scientists Use Reasoning, Imagination, and
Creativity to Learn How Nature Works
⦿ Important
scientific tools
• Inductive reasoning – uses specific observations and
measurements to arrive at a general conclusion or
hypothesis.
• Deductive reasoning – uses logic to arrive at a
specific conclusion based on a generalization or
premise.
⦿
Scientists also use
• Intuition
• Imagination
• Creativity
Scientific Theories and Laws Are the Most
Important Results of Science
theory – and explanation for natural
phenomena.
⦿ Scientific
• Widely tested
• Supported by extensive evidence
• Accepted by most scientists in a particular area
law, or law of nature – a well-tested
and widely accepted description of what we find
happening over and over again in the same way in
nature.
⦿ Paradigm shift – when new discoveries and new
ideas overthrow a well-accepted theory; occurs
when majority of scientist in the related fields a
⦿ Scientific
Science Focus: The Scientific
Consensus over Global Warming (1)
⦿ Greenhouse
effect, one of the most widely
accepted theories in atmospheric science.
⦿ Since 1980, many climatologist have been
focused on these questions:
• How much has the earth’s atmosphere warmed during
the last 50 years?
• How much of this warming is due to human activity?
• How much is the atmosphere likely to warm in the
future and will this affect climate?
⦿ The
UN and the World Meteorological
Organization established the IPCC
• Studies how climate systems work, document past
Science Focus: The Scientific
Consensus over Global Warming (2)
⦿ The
4th IPCC report, 2007
• Very likely (90-99% probability) that the troposphere is
getting warmer.
• Very likely (90-99% probability) that human activities
have been the cause.
• Very likely (90-99% probability) that temperatures will
increase by at least 3 oC between 2005 and 2100.
⦿ Report
is considered reliable science.
⦿ Some individual scientist disagree.
⦿ Media coverage causes bias by providing
balanced coverage.
The Results of Science Can Be
Tentative, Reliable, or Unreliable
science, or frontier science –
preliminary results that have not been widely
tested and accepted by peer review.
⦿ Reliable science – consists of data, hypotheses,
theories and laws that are widely accepted by
scientists who are considered experts in the field;
based on a self-correcting process.
⦿ Unreliable science – hypotheses and results that
are presented as reliable without having
undergone the rigors of peer review, or that have
been discarded as a result of peer review.
⦿ Tentative
• Questions to ask to help evaluate scientific claims, p. 34
The Results of Science Can Be
Tentative, Reliable, or Unreliable
⦿ Particular
hypotheses, theories, or laws have a
high probability of being true while not being
absolute.
• Can’t “prove” anything; there is always some degree of
uncertainty in measurements, observations and models.
⦿ Bias can be minimized by scientists.
⦿ Statistical methods may be used to estimate
very
large or very small numbers.
• Just because they are estimates, the numbers should not
be dismissed. The estimates can indicate important trends.
⦿ Environmental
phenomena involve interacting
variables and complex interactions.
⦿ Scientific process is limited to the natural world.
Science Focus: Statistics and
Probability
– mathematical tools used to
collect, organize, and interpret numerical data.
⦿ Statistics
⦿ Probability
- the chance that something will
happen or be valid.
⦿
Critical Thinking: What does it mean when an international body of the
world’s climate experts says that there is a 90-99% chance (probability of
0.90-0.99) that human activities, led by emissions of carbon dioxide from
burning fossil fuels, have been the main cause of the observed
atmospheric warming during the past 50 years? Why would the probability
never be 100%?
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
• The stuff that makes up life and its environments
⦿ Elements
• Unique properties
• Cannot be broken down chemically into other substances
• Four elements⎯O, C, H, and N⎯make up about 96% of the
mass of most organisms.
⦿ Compounds
• Two or more different elements bonded together in fixed
proportions
Elements Important to the Study
of Environmental Science
Atoms, Ions, and Molecules Are
the Building Blocks of Matter (1)
⦿ Atom – basic building block of matter; smallest unit of matter
into which an element can be divided and still retain its
chemical properties.
⦿ Atomic theory
⦿ Subatomic particles
•
•
Protons (p) with positive charge and neutrons (0) with no charge in
nucleus
Negatively charged electrons (e) orbit the nucleus
⦿ Mass number
•
Protons plus neutrons
Model of a Carbon-12 Atom
Atoms, Ions, and Molecules Are
the Building Blocks of Matter (2)
⦿ Ions
• Gain or lose
electrons
• Form ionic
compounds
⦿ pH
• Measure of
acidity
• H+ and OH-
Ions Important to the Study of
Environmental Science
Figure 2.4Loss of nitrate ions (NO3−) from a deforested watershed in the Hubbard
Brook Experimental Forest in New Hampshire (Figure 2-1, right). The average
concentration of nitrate ions in runoff from the deforested experimental watershed was
60 times greater than in a nearby unlogged watershed used as a control (Figure 2-1,
left). (Data from F. H. Bormann and Gene Likens)
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
⦿ Chemical
formula
Compounds Important to the
Study of Environmental Science
Organic Compounds are the
Chemicals of Life
⦿ Inorganic
⦿ Organic
compounds
compounds
• Hydrocarbons (compounds of C and H) like methane
• Chlorinated hydrocarbons (compounds of C, H and Cl)
like DDT (C14H9Cl5)
• Simple carbohydrates like glucose
• Macromolecules: complex organic molecules;
polymers made of subunit monomers.
⚫Complex carbohydrates (many simple sugars)
⚫Proteins (amino acids)
⚫Nucleic acids (nucleotides)
Matter Comes to Life through
Genes, Chromosomes, and Cells
⦿ The bridge between living
and nonliving lies
somewhere between
macromolecules 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
quality – measure of
how useful a form of matter is
to humans as a resource
based on availability and
concentration.
⦿ Matter
⦿ High-quality
matter
⦿ Low-quality
matter
Figure 2.6
Examples of differences in matter quality. High-quality
matter (left column) is fairly easy to extract and is
highly concentrated; low-quality matter (right column) is
not highly concentrated and is more difficult to extract
than high-quality matter.
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
Matter Undergoes Physical,
Chemical, and Nuclear Changes
change – chemical composition does
not change.
⦿ Physical
⦿ Chemical
⦿ Nuclear
change, chemical reaction
change
• Natural radioactive decay
⚫Radioisotopes: unstable
• Nuclear fission
⚫Chain reaction – when multiple fissions of a certain mass
occurs; releases enormous amounts of energy.
• Nuclear fusion
Figure 2-7 a
Figure 2-7 b
Figure 2-7 c
Modeling Radioactive Decay
We Cannot Create or Destroy
Matter
⦿ Law
of conservation of matter
⦿ What
•
•
is meant by matter consumption?
Matter is converted from one form to another.
No such thing as throwing 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
lower- quality or less usable energy than we
started with (second law of thermodynamics).
Energy Comes in Many Forms
⦿ What
is energy?
• Work = force x distance
⦿ Kinetic
energy
• Heat (textbook defines incorrectly.)
⚫Transferred by radiation, conduction, or convection
• Electromagnetic radiation
⦿ Potential
energy
• Stored energy
• Can be changed into kinetic energy
Figure 2.8Solar capital: the spectrum of electromagnetic
radiation released by the sun consists mostly of visible
light.
Some Types of Energy Are More
Useful Than Others
quality – a measure of an energy
source’s capacity to do useful work.
⦿ Energy
energy – concentrated w/ high
capacity to do work.
⦿ High-quality
• Examples: fossil fuels, high heat, strong wind, nuclear
fission.
energy – dispersed and little
capacity to do work.
⦿ Low-quality
• Examples: thermal energy in atmosphere and oceans.
Energy Changes Are Governed
by Two Scientific Laws (1)
⦿ Thermodynamics
is the study of energy
transformations.
⦿ First
Law of Thermodynamics
• Energy input always equals energy output
Energy Changes Are Governed
by Two Scientific Laws (2)
⦿ Second Law of Thermodynamics
• Energy always goes from a more useful to a less useful
form when it changes from one form to another.
• Energy quality is lost.
• Examples: 94% of energy in gas is degraded to heat, only
6% gets you to places. Only 5% of electrical energy
generates light in an incandescent bulb. Heat bulb?
⦿ Energy efficiency, or energy productivity
• This is a measure of how much useful work is done by a
particular input of energy into a system.
• 16% of energy in the US actually does useful work.
• 41% is unavoidable.
Figure 2.9The second law of thermodynamics in action in living systems. Each
time energy changes from one form to another, some of the initial input of highquality energy is degraded, usually to low-quality heat that is dispersed into the
environment.
2-5 What Are Systems and How
Do They Respond to Change?
⦿ 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
– a set of components that
function and interact in some regular way.
⦿ Most systems have the following key
components:
⦿ System
• Inputs from the environment
• Flows, or throughputs
• Outputs to the environment
Figure 2.10Inputs, throughput, and outputs of an economic system. Such
systems depend on inputs of matter and energy resources and outputs of
waste and heat to the environment. Such a system can become unsustainable
if the throughput of matter and energy resources exceeds the ability of the
earth’s natural capital to provide the required resource inputs or the ability of
the environment to assimilate or dilute the resulting heat, pollution, and
environmental degradation.
Systems Respond to Change
through Feedback Loops
– any process that increases
(positive feedback) or decreases (negative
feedback) a change to a systems.
⦿ Feedback loop – occurs when an output of
matter, energy or information is fed back
into the system as an input and leads to
changes in the system.
⦿ Feedback
• Positive feedback loop
• Negative, or corrective, feedback loop
Figure 2.11Positive feedback loop. Decreasing vegetation in a valley causes
increasing erosion and nutrient losses, which in turn causes more vegetation to
die, which allows for more erosion and nutrient losses. The system receives
feedback that continues the process of deforestation.
Figure 2.12Negative feedback loop. When a house being heated by a furnace
gets to a certain temperature, its thermostat is set to turn off the furnace, and
the house begins to cool instead of continuing to get warmer. When the house
temperature drops below the set point, this information is fed back, and the
furnace is turned on and runs until the desired temperature is reached. The
system receives feedback that reverses the process of heating or cooling.
Time Delays Can Allow a System
to Reach a Tipping Point
⦿ Complex
system often have time delays between
the input of a feedback stimulus and the response
to it.
• Time delays vary depending on the system.
⦿ Time
delays can allow and environmental problem
to build up to a tipping point, or threshold level.
• Causes a shift in the behavior of a system
• Examples: clearing vegetation, population growth, leaks
from toxic waste dumps, global climate change,
degradation of forests from long-term exposure to
pollutants.
System Effects Can Be Amplified
through Synergy
interaction, or synergy –
occurs when two or more processes
interact so that the combined effect is
greater than the sum of their separate
effects.
⦿ Synergistic
• Helpful
• Harmful
⚫E.g., Smoking and inhaling asbestos particles
Human Activities Can Have
Unintended Harmful Results
⦿ Deforested
⦿ Coral
reefs dying
⦿ Glaciers
⦿ Sea
areas turning to desert
melting
levels rising