Science is built up of facts, as a
house is built of stones; but an
accumulation of facts is no more a
science than a heap of stones is a
house.
Henri Poincare
Science
Chapter 2 Science, Matter, Energy,
and Systems
Key Concepts
• Scientists collect data, develop theories,
models and laws
• Matter is made up of atoms, elements and
molecules
• Law of conservation of matter
• First law of thermodynamics
• Second law of thermodynamics
• Systems have inputs, outputs and feedback
Science: A Search for Order
• Effort to discover how nature works
• Uses observations, measurements,
experiments
• Assumes that natural events follow causeand -effect
The Scientific Method
•
•
•
•
•
•
•
•
Identify problem
Literature search
Ask question to be investigated
Perform experiment
Analyze data (check for patterns)
Formulate hypothesis to explain data
Perform experiment to test hypothesis
Accept hypothesis/ Reject hypothesis Revise hypothesis
• Scientific Theory
Elements of the Experiment
• Variables: factors that affect processes in the
experiment
*independent variable- tested variable
** dependent variable- measured variable
• Only I variable is tested at a time
• Experimental group has independent variable
• Control group lacks tested variable (provides
basis for comparison)
Features of Scientific Processes
•
•
•
•
•
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Curiosity
Creativity
Critical thinking
Skepticism
Reproducibility
Peer review
Goals of Science
• Scientific theories: well-tested, widely
accepted related hypotheses
*may be revised with new info
• Scientific laws/law of nature: well-tested,
widely accepted descriptions of what is
found repeatedly in nature
*cannot be broken
• Models: simulation of a natural system
Results of Science
• Tentative/frontier science: results that are
not yet reliable (new findings)
• Reliable science: accepted by scientific
consensus
• Unreliable science: rejected by scientific
consensus (usually because results were not
reproducible)
Limits of Science
1. Scientists cannot prove or disprove anything
absolutely
2. Scientists are not totally free of bias
3. Natural systems involve too many variables
to control (important to environmental
science)
4. Statistical sampling is often used to estimate
measurements (think: probability)
5. Cannot be applied to ethical questions
Matter
• Anything with mass, volume
• Physical states: solid, liquid, gas
• Exists as an element (fundamental) or in
compounds (combinations of different
elements)
Atoms/Elements
• Basic unit of matter
*atomic theory: atoms make up elements
• Internal structures: neutrons (n), protons (p),
electrons (e)
• Atomic number: equals number of protons
• Mass number: total number of protons and
neutrons
• Isotopes: same atomic number, but different
mass
Helium
electron
N
+
proton
+
N
neutron
Atomic Number: 2
Atomic Mass: 4
Isotopes
Molecule/Compound
• Two or more different element chemical
bound
*covalent bond: valence electrons are shared
** ionic bond: movement of electrons
between ions
Covalent bond
Ionic bond
Ions
• Atom/group of atoms with a positive or
negative charge
(superscript indicates charge- NH₄⁺)
• Important for measuring acidity:
* determines how materials dissolve
** measured by pH:
0--------------------------7----------------------------14
More H⁺ than OH¯
More OH¯ than H⁺
Compounds
• Organic: contain at least 2 carbons
• Inorganic: all other compounds
Organic Compounds
•
•
•
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Hydrocarbons: C, H (methane-CH₄)
Chlorinated hydrocarbons: C, H, Cl (DDT)
Simple carbohydrates: C,H,O (glucose)
Macromolecules: complex carbohydrates,
porteins, nucleic acids and lipids
Macromolecules
Compound
Carbohydrate
Composed Function
of:
C,H,O
Examples
Releases energy Sugar
for cells
Starch
Cellulose
Macromolecules
Compound
Protein
(made up of
amino acids)
Composed
of:
C,H,O,N
Function
Building
blocks of cell,
enzymes
Examples
lactase
Macromolecules
Compound
Lipids
Composed
of:
C,H,O
Function
Examples
Stores and
releases
energy for
cell
(more than
carbs)
Fats, waxes,
oils
Macromolecules
Compound
Nucleic Acids
Composed
of:
C,H,O,N,P
Function
Examples
Stores
hereditary
material
DNA, RNA
Living Matter
• Cell: basic functioning unit of life (cell theory)
• Genes: sequences of nucleotides that code
for specific traits
• Chromosome: made up of thousands of
genes
Matter Quality
• Measure of how useful matter is to humans;
based on availability, concentration
* high quality matter: high concentration,
great resource, usually found near Earth’s
surface
** low quality matter: low concentration,
resource, deep underground or dispersed
Types of Change in Matter
• Physical change: no change in chemical
composition (ice melting)
• Chemical change/reaction: change in
chemical composition
Types of Change in Matter (cont’d)
• Nuclear change: change in the nuclei of atoms
• Radioactive decay: unstable isotope sheds
fast-moving particles
- half life: time needed for ½ of nuclei to decay
into a more stable form
• Nuclear fission: nuclei of isotopes with large
mass split into lighter nuclei
• Nuclear fusion: two isotopes of light
elements fuse to form a heavier nucleus
Nuclear Changes
Radioactive Half-Lives
Nuclear Changes
Fission
Fusion
Law of Conservation of Matter
• No atoms are created or destroyed when
matter undergoes physical or chemical
changes
(This law means we really cannot “throw”
away anything. Pollution changes form, but
never goes away)
Energy
• Capacity to do work or to transfer heat
• Kinetic energy: associated...
1. motion
2. heat (moving atoms; flow from cold to hot)
3. electromagnet radiation
a. travels in waves
b. wavelength reflects energy (shorter
waves = greater energy)
Energy (cont’d)
Electromagnetic Radiation
Energy (cont’d)
• Potential energy: stored (potential for us)
Natural/Commercial Energy Sources
• Sun is source for most energy on Earth
• Solar energy produces wind, hydropower,
biomass fuels
• Fossil fuels (oil, coal, natural gas) produces
commercial energy
Energy Quality
• High-quality energy: concentrated, high work
capacity
ex.s- high temperatures, direct sunlight,
burning coal
• Low-quality energy: dispersed, low work
capacity
ex.s- low temperatures, indirect sunlight,
burning crop wastes
Energy Quality
Laws of Energy Transfer
• First law of thermodynamics: no energy is
created or destroyed when energy is
converted from one form to another
• Second law of thermodynamics: energy
conversions always result in a less useful
form of energy due to loss in form of heat
(we can never reuse/recycle energy to do
work)
Systems
• Set of components that function and interact
in a regular way. Made up of:
• Inputs from the environment
• Flows/throughputs of matter or energy
within system
• Outputs to the environment
ex.s- human body, an economy, a river
Systems
Inputs:
Energy
Matter
Information
Throughputs
Outputs:
Work/Products
Waste
Heat
System Changes
• Feedback: process that increases (positive) or
decreases (negative) a change to a system
• Feedback loop: output is fed back into a
system as input; results in change to the
system
Positive Feedback Loop
• Causes system to increase change in same
direction
Ex:
Decreasing Vegetation
Nutrient Loss
Erosion
Negative Feedback Loop
• Causes a system to move in the opposite
direction from which it is moving
Warm house causes
ex:
thermostat to turn
furnace off
House
Warms
House Cools
Temperature drop
triggers thermostat to
turn furnace on
System Regulations
• Time delay: time between the input of a
feed- back stimulus and the system’s
response to it
ex. Replanting a forest to slow erosion
• Tipping point: point at which a system is
changed irreversibly
ex. Erosion results in so much nutrient loss
that land can no longer support trees
Synergy
• Synergistic interaction (synergy): interaction
of two or more processes to create a greater
effect than each process separately
(ex. Nonsmoker exposed to asbestos is 5 х
more likely to get cancer than a smoker; a
smoker exposed to asbestos is 50 х more
likely to get cancer than a nonsmoker)