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Energy and Matter: Flows, Cycles and Conservation

Energy and matter characterize both physical and biological systems. These systems are defined both by the types of energy and matter they contain and by how that matter and energy move through and between systems. In natural systems, both energy and matter are conserved within a system. This means that energy and matter can change forms but cannot be created or destroyed. Energy and matter are often cycled within a system, and different forms of matter and energy are able to interact. The surrounding environment must be considered when studying a system’s energy and matter to examine flow into and out of the system. Scientists seek to study the flow and interactions of matter and energy, while engineers often seek to minimize inputs and maximize outputs of matter and energy relative to a given system.


<p><strong>Fig 2.17.</strong> A diagram shows how mercury moves from land through a food chain in the ocean.</p><br />

Ocean and aquatic scientists and engineers study a variety of types of matter and energy. For example, biogeochemists describe how matter is cycled and energy is transformed at large and small scales. Biogeochemists might examine cycles of elements and compounds such as water, carbon, and mercury (Fig. 2.17). Some ecologists examine the variation in stages of decomposition of whale falls. Ocean engineers are developing ways to transform wind and wave energy at sea into usable electricity for people in coastal regions and beyond.


According to the framework, the crosscutting concept of energy and matter can be used to develop understanding across physical, life, and Earth science disciplines. Due to the abstract and complex nature of energy, the NGSS do not introduce energy concepts until grade three. At this level, students can understand the flow of energy into and out of systems. Matter can also be an abstract concept, especially at the molecular level. For this reason, the idea of atoms is not introduced in the NGSS until middle school. However, all students can observe and describe the transfer of matter at the macroscopic level. In middle and high school, the concept of the conversion of forms of matter and energy can be developed. Appropriate investigations can be used to address common misconceptions about matter and energy.


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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.