AP Environmental Science Review
A. Chapter 2: Science, Matter, Energy, and Systems
a. 2-1: What do Scientist Do?
i. Science – an attempt to discover how nature works and use that knowledge to describe
what is likely to happen in nature.
ii. Scientific Method:
1. Identify a Problem
2. Find out what is known about the problem
3. Ask a question to investigate
4. Perform and experiment and collect and analyze data to answer the question
5. Propose a hypothesis to explain the data
a. A possible and testable answer to a scientific question or explanation of
what scientist observe in nature
6. Use the hypothesis to make projections that can be tested
7. Test the projections with further experiments or observations
a. Model – an approximate representation or simulation of a system
8. Accept or revise the hypothesis
a. Scientific Theory – a well-tested and widely accepted scientific
hypothesis or a group of related hypothesis
iii. Four important features of the scientific process are curiosity, skepticism,
reproducibility, and peer review
iv. Thinking critically involves:
1. Be skeptical about everything you read or hear
2. Look at the evidence and evalutate it
3. Be open to many viewpoints
4. Identify and evaluate your personal assumptions, biases, and beliefs
v. Scientific Law (Law of Nature) – a well-tested and widely accepted description of what
we find happening repeatedly and in the same way in nature.
1. Example: Law of gravity
2. We CANNOT break a scientific law
vi. Tentative Science (Frontier Science) - Preliminary scientific results that capture news
headlines have not been widely tested and accepted by peer review.
vii. Reliable Science – consists of data, hypothesis, models, theories, and laws that are
widely accepted by all or most of the scientist who are considered experts in the field
under study.
viii. Unreliable Science - scientific hypothesis and results that are presented as reliable
without having undergone the rigors of widespread peer review, or that have been
discarded as a result of peer review.
ix. Science has 4 important limitations:
1. Scientist cannot prove or disprove anything absolutely instead they try to
establish a theory or law that has a high probability or certainty of being useful
2. Scientist are human and thus are not totally free of bias about their own results
and hypothesis
3. Many systems in the natural world involve a huge number of variables with
complex interactions
4. The use of statistical tools
a. Example: No way to measure accurately how many metric tons of soil are
eroded annually worldwide
b. 2-2: What is Matter and What Happens When It Undergoes Change?
i. Matter – anything that has mass and takes up space
1. Exists in three physical states: Solid, Liquid, Gas
2. Two chemical forms: Elements and Compounds
a. Element – a fundamental type of matter that has a unique set of
properties and cannot be broken down into simpler substances by
chemical means.
b. Compounds –combinations of tow or more different elements held
together in fixed proportions
3. Atom – the most basic building block of matter
a. The idea that all elements are made up of atoms is called the atomic
theory
b. 3 subatomic particles:
i. Neutrons (n) – no electrical charge
ii. Protons (p) – has a positive charge (+)
iii. Electrons (e) – has a negative charge (-)
c. Extremely small center called the nucleus
d. Electron Probability Cloud – we do not know the exact locations, but the
cloud represents an area in which there is a high probability of finding
them
e. An atom in its basic form has no net electrical charge
f. Atomic Number – equal to the number of protons in the nucleus of its
atom
g. Mass Number – the total number of neutrons and protons in its nucleus
i. Most of the atom’s mass is concentrated in its nucleus
4. Isotopes - Forms of an element having the same atomic number but different
mass numbers
5. Molecule – a combination of two or more atoms of the same or different
elements held together by forces called chemical bonds (Ex. H2O)
6. Ion – an atom or a group of atoms with one or more net positive or negative
electrical charges (Ex. NO3-)
a. Important for measuring a substance’s acidity in a water solution.
i. A chemical characteristic that helps determine how a substance
dissolved in water will interact with and affect its environment
1. Hydrogen (H+) and Hydroxide (OH-)
ii. pH is a measure of acidity
1. Neutral Solution – has a pH of 7
2. Acidic Solution – has a pH less than 7
3. Basic Solution – has a pH greater than 7
7. Chemical Formula – is written to show the number of each type of atom or ion
in a compound.
ii. Organic Compounds – because they contain at least two carbon atoms
1. Methane (CH4) – has only one carbon atom but is considered an organic
compound
2. Hydrocarbons – compounds of carbon and hydrogen
3. Chlorinated Hydrocarbons – compounds of carbon, hydrogen, and chlorine
4. Simple Carbohydrates (simple sugars) – certain types of compounds of carbon,
hydrogen, and oxygen atoms
5. Large and more complex organic compounds, essential to life, are composed of
macromolecules
a. Some of these are called polymers – formed when a number of simple
organic molecules (monomers) are linked together by chemical bonds
i. Complex Carbohydrates – cellulose and starch
ii. Proteins – amino acids
iii. Nucleic Acids – nucleotides
iv. Lipids – fats, waxes, that are not made of monomers but are a
fourth type of macromolecule essential for life
iii. Inorganic Compounds – all other compounds without the carbon bond
iv. Cells – the fundamental structural and functional units of life
1. Cell Theory - The idea that all living things are composed of cells
2. Genes – contains instructions, or codes, called genetic information, for making
specific proteins
3. Trait – or characteristic, passed on from parents to offspring during
reproduction in an animal or plant
4. Chromosome – thousands of genes make up a single chromosome
v. Physical Change – when there is no change in the chemical composition
vi. Chemical Change (Chemical Reaction) – there is a change in the chemical composition
of the substances involved.
vii. Matter can undergo three types of change or nuclear change – change in the nuclei of
its atom
1. Radioactive Decay: spontaneously emit fast-moving chunks of matter
2. Nuclear Fission – occurs when the nuclei split apart
3. Nuclear Fusion – two nuclei are forced together
viii. Law of Conservation of Matter: whenever matter undergoes a physical or chemical
change, no atoms are created or destroyed.
1. We can change elements and compounds from one physical or chemical form to
another, but we cannot create or destroy any of the atoms involved in any
physical or chemical change.
c. 2-3: What is Energy and What Happens When it Undergoes Change?
i. Work – done when any object is moved to a certain distance
1. Work = Force X Distance
ii. Energy – the capacity to do work or to transfer heat
1. Kinetic Energy – matter in motion
a. Heat/Thermal Energy – a form of kinetic energy, the total kinetic energy
of all moving atoms, ions, or molecules of an object
i. Molecules move faster, it will become warmer
ii. Heat flows from the warmer object to the cooler object
b. Electromagnetic radiation – a form of kinetic energy, many different
forms of electromagnetic radiation, each form having a different
wavelength and energy content
2. Potential Energy – stored and potentially available for use
a. We can change potential to kinetic
iii. Divide energy resources into 2 categories:
1. Renewable Resources – energy gained from resources that are replenished by
natural processes in a relatively short time
a. Indirect forms of renewable solar energy:
i. Wind, Hydropower, Biomass
2. Nonrenewable Resources – energy from resources that can be depleted and are
not replenished by natural processes within a human time scale.
a. Fossil Fuels – oil, coal, and natural gas
iv. Commercial Energy – energy that is sold in the marketplace
v. Energy Quality – a measure of the capacity of a type of energy to do useful work
1. High Quality Energy – concentrated energy that has a high capacity to do useful
work
2. Low Quality Energy – energy that is so dispersed that it has little capacity to do
useful work
vi. Laws of Thermodynamics:
1. 1st Law of Thermodynamics – Law of Conservation of Energy – whenever
energy is converted from one form to another in a physical or chemical change,
no energy is created or destroyed.
2. 2nd Law of Thermodynamics – whenever energy is converted from one form to
another in a physical or chemical change, we end up with lower-quality or less
useable energy than we started with – usually this loss takes the form of heat
that flows into the environment
vii. To improve our energy efficiency – which means getting more work out of the energy
we use – we need to stop wasting ½ the energy we use
d. 2-4: What are Systems and How Do They Respond to Change?
i. System – a set of components that function and interact in some regular way
1. Inputs – matter and energy from the environment
2. Flows/Throughputs – matter and energy within the system
3. Outputs – matter and energy to the environment
a. Feedback – any process that increases (positive feedback) or decreases
(negative feedback) a change to a system
b. 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 that system
i. Positive Feedback Loop – causes a system to change further in the
same direction
1. Example: the melting of the polar ice caps
ii. Negative/Corrective Feedback Loops – causes a system to change
in the opposite direction from which it is moving
1. Example: A thermostat or recycling and reuse
4. Time Delay – or lack of response during a period of time between the input of a
feedback stimulus and the system’s response to it
a. Can allow an environmental problem to build up slowly until it reaches a
threshold level (tipping point – the point at which a fundamental shift in
the behavior of a system occurs)
b. Prolonged Delays – dampen the negative feedback mechanisms that
might slow, prevent, or halt environmental problems
5. Synergistic Interaction (Synergy) – can be positive or negative, occurs when two
or more processes interact so that the combined effect is greater than the sum
of their separate effects