Mechanism and explanation. Events have causes, sometimes simple, sometimes multifaceted. A major activity of science is investigating and explaining causal relationships and the mechanisms by which they are mediated. Such mechanisms can then be tested across given contexts and used to predict and explain events in new contexts.
Science & Engineering Practices
Asking Questions and Defining Problems
Students at any grade level should be able to ask questions of each other about the texts they read, the features of the phenomena they observe, and the conclusions they draw from their models or scientific investigations. For engineering, they should ask questions to define the problem to be solved and to elicit ideas that lead to the constraints and specifications for its solution. (NRC Framework 2012, p. 56)
Constructing Explanations and Designing Solutions
The goal of science is the construction of theories that provide explanatory accounts of the world. A theory becomes accepted when it has multiple lines of empirical evidence and greater explanatory power of phenomena than previous theories.”(NRC Framework, 2012, p. 52)
Engaging in Argument from Evidence
The study of science and engineering should produce a sense of the process of argument necessary for advancing and defending a new idea or an explanation of a phenomenon and the norms for conducting such arguments. In that spirit, students should argue for the explanations they construct, defend their interpretations of the associated data, and advocate for the designs they propose. (NRC Framework, 2012, p. 73)
Generating a Hypothesis and Developing a Model
Modeling can begin in the earliest grades, with students’ models progressing from concrete “pictures” and/or physical scale models (e.g., a toy car) to more abstract representations of relevant relationships in later grades, such as a diagram representing forces on a particular object in a system. (NRC Framework, 2012, p. 58)
adhesion - the tendency of molecules to stick to substances that are dissimilar.
anion - a negatively charged ion.
cation - a positively charged ion.
chemical bond - an electrical interaction between the positively charged nuclei and the negatively charged electrons of atoms that forms when the force of attraction is stronger than the force of repulsion.
cohesion - the action or property of like molecules sticking together, being mutually attractive.
covalent bond - a bond in which pairs of electrons are shared between atoms, instead of being transferred from one atom to another.
double covalent bond - a bond in which atoms share two pairs of electrons.
electronegativity - the ability of an atom to attract additional electrons.
electrostatic force - a force in which oppositely charged particles are attracted to each other, while like charges repel each other.
intermolecular forces - the attractive forces acting between molecules.
intramolecular bond - a bond that is occuring within a molecule.
ion - an atom with a positive or negative charge.
ionic bond - a bond that occurs between atoms, through the transfer of electrons, when a positively charged atom and negatively charged atom are attracted to one another.
molecule - a group of atoms that have chemically bonded and behave as an individual unit.
nonpolar covalent bond - a bond that forms between atoms in which their electrons are shared equally.
octet rule - when an ion or an atom has eight valence electrons, it is at its most stable electron configuration.
polar covalent bond - a bond in which electrons are shared unequally between atoms.
single covalent bond - a bond in which atoms share only one pair of electrons.
triple covalent bond - A bond in which atoms share three pairs of electrons.
valence electrons - the electrons found in the outermost electron shell of an atom.
Georgia Standards of Excellence
SC2Obtain, evaluate, and communicate information about the chemical and physical properties of matter resulting from the ability of atoms to form bonds.
SC2.aPlan and carry out an investigation to gather evidence to compare the physical and chemical properties at the macroscopic scale to infer the strength of intermolecular and intramolecular forces.
SC2.bConstruct an argument by applying principles of inter- and intra- molecular forces to identify substances based on chemical and physical properties.
SC2.cConstruct an explanation about the importance of molecular-level structure in the functioning of designed materials. (Clarification statement: Examples could include why electrically conductive materials are often made of metal, flexible but durable materials are made up of long chained molecules, and pharmaceuticals are designed to interact with specific receptors.)
SC2.dDevelop and use models to evaluate bonding configurations from nonpolar covalent to ionic bonding. (Clarification statement: VSEPR theory is not addressed in this element.)
SPS2Obtain, evaluate, and communicate information to explain how atoms bond to form stable compounds.
SPS2.aAnalyze and interpret data to predict properties of ionic and covalent compounds. (Clarification statement: Properties are limited to types of bonds formed, elemental composition, melting point, boiling point, and conductivity.)
SPS2.bDevelop and use models to predict formulas for stable, binary ionic compounds based on balance of charges.
SPS2.cUse the International Union of Pure and Applied Chemistry (IUPAC) nomenclature for translating between chemical names and chemical formulas.
(Clarification statement: Limited to binary covalent and binary ionic, containing main group elements, compounds but excludes polyatomic ions.)
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