The Law of Conservation of Mass
The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that
mass is neither created nor destroyed in chemical reactions. In other words, the mass
of any one element at the beginning of a reaction will equal the mass of that element at
the end of the reaction. If we account for all reactants and products in a chemical
reaction, the total mass will be the same at any point in time in any closed system.
Lavoisier's finding laid the foundation for modern chemistry and revolutionized
science. QUESTION 1
The Law of Conservation of Mass holds true because naturally occurring elements are
very stable at the conditions found on the surface of the Earth. in the everyday world
of Earth, from mountain to the deepest ocean, atoms are not converted to other
elements during chemical reactions. Because of this, individual atoms that make up
living and nonliving matter are very old. Carbon may have spent 65 million years
buried as coal before being burned in a power plant, followed by two decades in
Earth's atmosphere before being dissolved in the ocean, and then taken up by algae
before being respired into Earth's atmosphere. (Figure 1). QUESTION 2
Life and the Law of Conservation of Mass
(Figure 2)
Life involves obtaining, utilizing, and disposing of elements. The biomolecules for the
building blocks of life are proteins, lipids, carbohydrates, and nucleic acids. Living
organisms are primarily made of six elements: oxygen, carbon, Hydrogen, nitrogen,
calcium, and phosphorus. Each element travels through the stage of input,
compartment, or output throughout the matter cycle. QUESTIONS 3-4
Mass Balance of Elements in Organisms
The availability of individual elements can vary a great deal between nonliving and
living matter. Life on Earth depends on the recycling of essential chemical elements.
While an organism is alive, its chemical makeup is replaced continuously. When an
organism dies, the atoms that were bound in biomolecules return to simpler molecules
in the atmosphere, water and soil through the action of decomposers.
Obtaining the resources required for metabolism, growth, and reproduction is one of
the central challenges of life. Sometimes this may result in deficiencies. For example,
researchers have shown that the crickets migrate in search of protein and salt.
Crickets stop walking once their demand for protein is met. QUESTIONS 5-6
Mass Balance in Watersheds
A forested watershed receives inputs of carbon through photosynthesis, inputs of
nitrogen from nitrogen-fixing bacteria, as well as through the deposition of
atmospheric nitrogen, inputs of phosphorus from the slow weathering of bedrock, and
inputs of water from precipitation. Outputs include gaseous pathways such as H2O
losses through transpiration; CO2 production as respiration; and N2 produced by
denitrifying bacteria. QUESTIONS 7-10
Mass Balance in Human-Dominated Ecosystems
Cities import food, fuel, water, and other materials and export materials such as
manufactured goods. Cities also produce large quantities of waste products — with
solid waste sent to landfills, CO2, and other pollutants produced from the combustion of
fossil fuels being released to the atmosphere. QUESTIONS 11-12
http://www.nature.com/scitable/knowledge/library/the-conservation-of-mass-17395478
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1. Write the Law of Conservation of Mass in ten words or less.
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2. What happens to an atom as it cycles through the environment?
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3. What are the four biomolecules for life?
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4. Living organisms are primarily made up of how many elements?
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5. What happens to the elements in an organism while it is alive?
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6. What happens to the elements when an organism dies?
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7. What are two input functions in a watershed?
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________
8. What is the output pathway function for gaseous water?
_________________
9. What is the output method for CO2?
__________________
10.What is the output method for nitrogen?
________________
11.What are two input sources in cities? Be specific
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12.What are two outputs of cities?
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Answer Key
1. Write the Law of Conservation of Mass in ten words or less.
Matter can neither be created nor destroyed.
Atoms in the beginning must equal atoms in the end.
2. What happens to an atom as it cycles through the environment?
The atom itself is neither created nor destroyed, but cycles among chemical
/ scitable
uninitedaudio
compounds.
3. What are the four biomolecules for life?
proteins, lipids, carbohydrates, and nucleic acids.
4. Living organisms are primarily made up of how many elements?
Six
5. What happens to the elements in an organism while it is alive?
The elements are replaced continuously.
6. What happens to the elements when an organism dies?
The biomolecules break down into elements through the action of decomposers.
7. What are two input functions in a watershed?
photosynthesis, bacteria, deposition, weathering, precipitation
8. What is the output pathway function for gaseous water?
transpiration
9. What is the output method for CO2?
respiration
10.What is the output method for nitrogen?
Bacteria
11.What are two input sources in cities? Be specific
Cities import food, fuel, water
12.What are two outputs of cities?
solid waste, CO2, other pollutants