Many have asserted that the water we drink is exactly the same water that has been eliminated from the bodies of humans and animals from the past. The argument goes that water excreted from our bodies by exhalation or urine ultimately ends up back in the water cycle. That is, water eliminated from biological organisms finds its way into rivers, lakes, ponds, and oceans. This same water evaporates back into the atmosphere, and rains back down onto the Earth in an endless cycle. Because the water we consume comes from water that participates in this timeless process, it stands to reason that we drink water molecules that have been excreted from Muhammad Ali, Gandhi, Marie Curie, and even the dinosaurs!
I think chemistry informs this argument in an interesting way. Consider that water on Earth participates in a variety of chemical reactions such as photosynthesis (Equation 1):1
6 CO2 + 6 H2O → C6H12O6 + 6 O2 Equation 1
Notice that water molecules are consumed – in a sense, destroyed – during photosynthesis. In fact, during the first chemical step of photosynthesis, light energy is used to oxidize water into oxygen gas, removing hydrogen from the water in the process (Equation 2):1
2 H2O → O2 + 4 H+ + 4e- Equation 2
Consider a single water molecule involved in this process. The two specific hydrogen atoms and specific oxygen atom contained in this water molecule become separated, with the oxygen atom combining with another oxygen atom to make O2. As a result, the two water molecules have entirely lost their chemical identities. Certainly, the O2, protons, and electrons formed become extremely well mixed as they participate in a variety of other physical and chemical processes after separation.
The reverse of these processes happens in respiration, during which brand new water molecules are created (Equations 3 – 4):
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O Equation 3
O2 + 4 H+ + 4e- → 2 H2O Equation 4
Furthermore, water molecules are created or destroyed in a whole host of geochemical process,2 one of which is displayed below (Equation 5):
CaAl2Si2O8 + H2O + CO2 + ½ O2 → Al2Si2O5(OH)4 + CaCO3 Equation 5
Finally, consider that water molecules undergo hydrogen atom exchange reactions during which they do exactly that: trade hydrogen atoms with neighboring water molecules.3,4 Such reactions can be monitored using deuterated water, D2O (Equation 6):5
D2O + H2O → 2 HDO Equation 6
These exchange reactions happen very quickly, on the timescale of picoseconds,4 and can also occur between water and amines, alcohols, and acids.5
I made a short video that succinctly describes how chemistry informs the assertion that we drink dinosaur pee (Video 1).6
Video 1: Drinking dinosaur pee?!, Tommy Technetium YouTube Channel, November 22, 2023
After viewing this video, one person commented that my argument brings to mind The Ship of Theseus,7 a philosophical thought experiment. The Ship of Theseus poses the question: “If the component parts of an object are completely replaced, does the identity of the object remain the same?”. What do you think? Is it appropriate to say that we drink the same water molecules that the dinosaurs drank and peed out? Regardless, I hope you consider the chemistry involved when you think about how you might answer this question.
References:
- https://pubs.acs.org/doi/epdf/10.1021/acs.chemrev.5b00340
- Drever, A. I. The Geochemistry of Natural Waters: surface and groundwater environments, 3rd ed., Prentice Hall, Inc. 1997.
- https://www.pnas.org/doi/10.1073/pnas.1306642110
- https://pubs.acs.org/doi/epdf/10.1021/acscentsci.9b00603
- https://pubs.acs.org/doi/abs/10.1021/ja01652a030
- Drinking Dinosaur Pee?!, Tommy Technetium YouTube Channel
- https://en.wikipedia.org/wiki/Ship_of_Theseus
NGSS
Asking questions and defining problems in grades 9–12 builds from grades K–8 experiences and progresses to formulating, refining, and evaluating empirically testable questions and design problems using models and simulations.
Asking questions and defining problems in grades 9–12 builds from grades K–8 experiences and progresses to formulating, refining, and evaluating empirically testable questions and design problems using models and simulations.
questions that challenge the premise(s) of an argument, the interpretation of a data set, or the suitability of a design.
Scientific questions arise in a variety of ways. They can be driven by curiosity about the world (e.g., Why is the sky blue?). They can be inspired by a model’s or theory’s predictions or by attempts to extend or refine a model or theory (e.g., How does the particle model of matter explain the incompressibility of liquids?). Or they can result from the need to provide better solutions to a problem. For example, the question of why it is impossible to siphon water above a height of 32 feet led Evangelista Torricelli (17th-century inventor of the barometer) to his discoveries about the atmosphere and the identification of a vacuum.
Questions are also important in engineering. Engineers must be able to ask probing questions in order to define an engineering problem. For example, they may ask: What is the need or desire that underlies the problem? What are the criteria (specifications) for a successful solution? What are the constraints? Other questions arise when generating possible solutions: Will this solution meet the design criteria? Can two or more ideas be combined to produce a better solution?
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories.
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories. Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students’ own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories.
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories. Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students’ own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.
Engaging in argument from evidence in 9–12 builds on K–8 experiences and progresses to using appropriate and sufficient evidence and scientific reasoning to defend and critique claims and explanations about natural and designed worlds. Arguments may also come from current scientific or historical episodes in science.
Engaging in argument from evidence in 9–12 builds on K–8 experiences and progresses to using appropriate and sufficient evidence and scientific reasoning to defend and critique claims and explanations about natural and designed worlds. Arguments may also come from current scientific or historical episodes in science.
Evaluate the claims, evidence, and reasoning behind currently accepted explanations or solutions to determine the merits of arguments.
Earth’s Place in the Universe, help students formulate an answer to the question: “What is the universe, and what is Earth’s place in it?” The ESS1 Disciplinary Core Idea from the NRC Framework is broken down into three sub-ideas: the universe and its stars, Earth and the solar system and the history of planet Earth. Students examine the processes governing the formation, evolution, and workings of the solar system and universe. Some concepts studied are fundamental to science, such as understanding how the matter of our world formed during the Big Bang and within the cores of stars. Others concepts are practical, such as understanding how short-term changes in the behavior of our sun directly affect humans. Engineering and technology play a large role here in obtaining and analyzing the data that support the theories of the formation of the solar system and universe. The crosscutting concepts of patterns, scale, proportion, and quantity, energy and matter, and stability and change are called out as organizing concepts for these disciplinary core ideas. In the ESS1 performance expectations, students are expected to demonstrate proficiency in developing and using models, using mathematical and computational thinking, constructing explanations and designing solutions, engaging in argument, and obtaining, evaluating and communicating information; and to use these practices to demonstrate understanding of the core ideas.
More information about this category of NGSS can be found at https://www.nextgenscience.org/dci-arrangement/hs-ess1-earths-place-univ....
Earth’s Place in the Universe, help studentsformulate an answer to the question: “What is the universe, and what is Earth’s place in it?”The ESS1 Disciplinary Core Idea from the NRC Framework is broken down into three sub-ideas: the universe and its stars, Earth and the solar system and the history of planet Earth. Students examine the processes governing the formation, evolution, and workings of the solar system and universe. Some concepts studied are fundamental to science, such as understanding how the matter of our world formed during the Big Bang and within the cores of stars. Others concepts are practical, such as understanding how short-term changes in the behavior of our sun directly affect humans. Engineering and technology play a large role here in obtaining and analyzing the data that support the theories of the formation of the solar system and universe. The crosscutting concepts of patterns, scale, proportion, and quantity, energy and matter, and stability and change are called out as organizing concepts for these disciplinary core ideas. In the ESS1 performance expectations, students are expected to demonstrate proficiency in developing and using models, using mathematical and computational thinking, constructing explanations and designing solutions, engaging in argument, and obtaining, evaluating and communicating information; and to use these practices to demonstrate understanding of the core ideas.
Earth’s Systems, help students formulate an answer to the question: “How and why is Earth constantly changing?” The ESS2 Disciplinary Core Ideafrom the NRC Framework is broken down into five sub-ideas: Earth materials and systems, plate tectonics and large-scale system interactions, the roles of water in Earth’s surface processes, weather and climate, and biogeology. For the purpose of the NGSS, biogeology has been addressed within the life science standards. Students develop models and explanations for the ways that feedbacks between different Earth systems control the appearance of Earth’ssurface. Central to this is the tension between internal systems, which are largely responsiblefor creating land at Earth’s surface, and the sun-driven surface systems that tear down the land through weathering and erosion. Students begin to examine the ways that human activities cause feedbacks that create changes to other systems. Students understand the system interactions that control weather and climate, with a major emphasis on the mechanisms and implications of climate change. Students model the flow of energy between different components of the weather system and how this affects chemical cycles such as the carbon cycle. The crosscutting concepts of cause and effect, energy and matter, structure and function and stability and change are called out as organizing concepts for these disciplinary core ideas. In the ESS2 performance expectations, students are expected to demonstrate proficiency in developing and using models, planning and carrying out investigations, analyzing and interpreting data, and engaging in argument; and to use these practices to demonstrate understanding of the core ideas.
More information about all DCI for HS-ESS2 can be found https://www.nextgenscience.org/dci-arrangement/hs-ess2-earths-systems.
Earth’s Systems, help students formulate an answer to the question: “How and why is Earth constantly changing?” The ESS2 Disciplinary Core Ideafrom the NRC Framework is broken down into five sub-ideas: Earth materials and systems, plate tectonics and large-scale system interactions, the roles of water in Earth’s surface processes, weather and climate, and biogeology. For the purpose of the NGSS, biogeology has been addressed within the life science standards. Students develop models and explanations for the ways that feedbacks between different Earth systems control the appearance of Earth’ssurface. Central to this is the tension between internal systems, which are largely responsiblefor creating land at Earth’s surface, and the sun-driven surface systems that tear down the land through weathering and erosion. Students begin to examine the ways that human activities cause feedbacks that create changes to other systems. Students understand the system interactions that control weather and climate, with a major emphasis on the mechanisms and implications of climate change. Students model the flow of energy between different components of the weather system and how this affects chemical cycles such as the carbon cycle. The crosscutting concepts of cause and effect, energy and matter, structure and function and stability and change are called out as organizing concepts for these disciplinary core ideas. In the ESS2 performance expectations, students are expected to demonstrate proficiency in developing and using models, planning and carrying out investigations, analyzing and interpreting data, and engaging in argument; and to use these practices to demonstrate understanding of the core ideas.
Students who demonstrate understanding can plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.
More information about all DCI for HS-ESS2 can be found https://www.nextgenscience.org/dci-arrangement/hs-ess2-earths-systemsand further resources athttps://www.nextgenscience.org.
Students who demonstrate understanding can plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.
Emphasis is on mechanical and chemical investigations with water and a variety of solid materials to provide the evidence for connections between the hydrologic cycle and system interactions commonly known as the rock cycle. Examples of mechanical investigations include stream transportation and deposition using a stream table, erosion using variations in soil moisture content, or frost wedging by the expansion of water as it freezes. Examples of chemical investigations include chemical weathering and recrystallization (by testing the solubility of different materials) or melt generation (by examining how water lowers the melting temperature of most solids).
Construct an argument based on evidence about the simultaneous coevolution ofEarth’s systems and life on Earth.
*More information about all DCI for HS-PS1 can be found at https://www.nextgenscience.org/dci-arrangement/hs-ess2-earths-systems and further resources at https://www.nextgenscience.org.
Construct an argument based on evidence about the simultaneous coevolution ofEarth’s systems and life on Earth.
Assessment does not include a comprehensive understanding of the mechanisms of how the biosphere interacts with all of Earth’s other systems.
Emphasis is on the dynamic causes, effects, and feedbacks between the biosphere and Earth’s other systems, whereby geoscience factors control the evolution of life, which in turn continuously alters Earth’s surface. Examples include how photosynthetic life altered the atmosphere through the production of oxygen, which in turn increased weathering rates and allowed for the evolution of animal life; how microbial life on land increased the formation of soil, which in turn allowed for the evolution of land plants; or how the evolution of corals created reefs that altered patterns of erosion and deposition along coastlines and provided habitats for the evolution of new life forms.
Matter and its Interactions help students formulate an answer to the question, “How can one explain the structure, properties, and interactions of matter?” The PS1 Disciplinary Core Idea from the NRC Framework is broken down into three subideas: the structure and properties of matter, chemical reactions, and nuclear processes. Students are expected to develop understanding of the substructure of atoms and to provide more mechanistic explanations of the properties of substances. Chemical reactions, including rates of reactions and energy changes, can be understood by students at this level in terms of the collisions of molecules and the rearrangements of atoms. Students are able to use the periodic table as a tool to explain and predict the properties of elements. Using this expanded knowledge of chemical reactions, students are able to explain important biological and geophysical phenomena. Phenomena involving nuclei are also important to understand, as they explain the formation and abundance of the elements, radioactivity, the release of energy from the sun and other stars, and the generation of nuclear power. Students are also able to apply an understanding of the process of optimization in engineering design to chemical reaction systems. The crosscutting concepts of patterns, energy and matter, and stability and change are called out as organizing concepts for these disciplinary core ideas. In the PS1 performance expectations, students are expected to demonstrate proficiency in developing and using models, planning and conducting investigations, using mathematical thinking, and constructing explanations and designing solutions; and to use these practices to demonstrate understanding of the core ideas.
*More information about this category of NGSS can be found at https://www.nextgenscience.org/dci-arrangement/hs-ps1-matter-and-its-interactions.
"Matter and its Interactions help students formulate an answer to the question, “How can one explain the structure, properties, and interactions of matter?” The PS1 Disciplinary Core Idea from the NRC Framework is broken down into three subideas: the structure and properties of matter, chemical reactions, and nuclear processes. Students are expected to develop understanding of the substructure of atoms and to provide more mechanistic explanations of the properties of substances. Chemical reactions, including rates of reactions and energy changes, can be understood by students at this level in terms of the collisions of molecules and the rearrangements of atoms. Students are able to use the periodic table as a tool to explain and predict the properties of elements. Using this expanded knowledge of chemical reactions, students are able to explain important biological and geophysical phenomena. Phenomena involving nuclei are also important to understand, as they explain the formation and abundance of the elements, radioactivity, the release of energy from the sun and other stars, and the generation of nuclear power. Students are also able to apply an understanding of the process of optimization in engineering design to chemical reaction systems. The crosscutting concepts of patterns, energy and matter, and stability and change are called out as organizing concepts for these disciplinary core ideas. In the PS1 performance expectations, students are expected to demonstrate proficiency in developing and using models, planning and conducting investigations, using mathematical thinking, and constructing explanations and designing solutions; and to use these practices to demonstrate understanding of the core ideas."
Students who demonstrate understanding can construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
*More information about all DCI for HS-PS1 can be found at https://www.nextgenscience.org/dci-arrangement/hs-ps1-matter-and-its-interactions and further resources at https://www.nextgenscience.org.
Students who demonstrate understanding can construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
Assessment is limited to chemical reactions involving main group elements and combustion reactions.
Examples of chemical reactions could include the reaction of sodium and chlorine, of carbon and oxygen, or of carbon and hydrogen.
Evaluate a Solution to a Real World Problem is a performance expectation related to Engineering Design HS-ETS1.
Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics as well as possible social, cultural, and environmental impacts.
Evaluating potential solutions-In their evaluation of a complex real-world problem, students: Generate a list of three or more realistic criteria and two or more constraints, including such relevant factors as cost, safety, reliability, and aesthetics that specifies an acceptable solution to a complex real-world problem; Assign priorities for each criterion and constraint that allows for a logical and systematic evaluation of alternative solution proposals; Analyze (quantitatively where appropriate) and describe* the strengths and weaknesses of the solution with respect to each criterion and constraint, as well as social and cultural acceptability and environmental impacts; Describe possible barriers to implementing each solution, such as cultural, economic, or other sources of resistance to potential solutions; and Provide an evidence-based decision of which solution is optimum, based on prioritized criteria, analysis of the strengths and weaknesses (costs and benefits) of each solution, and barriers to be overcome.
Refining and/or optimizing the design solution: In their evaluation, students describe which parts of the complex real-world problem may remain even if the proposed solution is implemented.