Review Questions: Possible Answers
What are the six key elements in living organisms, and where does each occur—in the atmosphere,
hydrosphere, or lithosphere?
Nitrogen, carbon, oxygen, hydrogen, phosphorus, and sulfur are the key elements in nature.
Each is found in all living things and detritus.
All six elements are found in the atmosphere,
hydrosphere, and lithosphere.
Carbon is primarily found in the atmosphere. Phosphorus and sulfur are
primarily found in the lithosphere.
What is the “common denominator” that distinguishes between organic and inorganic molecules?
The common denominator that distinguishes organic and inorganic molecules is carbon-
carbon, carbon-hydrogen, and carbon-oxygen bonds.
In one sentence define matter and energy, and demonstrate how they are related.
Matter is anything that occupies space and has mass, while energy is the ability to move
“On a molecular level, changes in state are actually movements of atoms or molecules.
instance, the degree of heat energy contained in a substance is a measure of the relative vibrational
motion of the atoms and molecules of the substance.”
Give four examples of potential energy.
In each case, how can the potential energy be converted into
Water behind a dam—release the water.
Coal—burn the coal.
A stretched rubber band—
release the rubber band. A leaf attached to a tree—the leaf falls.
State the two energy laws.
How do they relate to entropy?
The First Law of Thermodynamics: “Energy is neither created nor destroyed, but may be
converted from one form to another.”
The Second Law of Thermodynamics: “In any energy
conversion, some of the usable energy is always lost.”
“Entropy is a measure of the degree of disorder
in a system, so increasing entropy means increasing disorder. With energy inputs, everything goes in
one direction only
toward increasing entropy.” The lost energy described in the second law is the
In order to keep anything organized, you must put energy in because everything moves to
Energy that has been converted from one form to another may include heat energy.
dissipates it disperses, thus becoming more disordered.
What is the chemical equation for photosynthesis?
Examine the origin and destination of each
molecule referred to in the equation.
Do the same for cell respiration.
: Carbon dioxide plus water plus sunlight gives glucose plus oxygen.
carbon dioxide originates from respiration, including the burning of glucose in cells, decomposition,
the burning of biomass and fossil fuels, and so forth.
Water originates from soil, streams, and so forth
in the hydrological cycle.
The oxygen that is released is used in combustion and in respiration.
glucose is burned during respiration.