PS1.A: Structure and Properties of Matter

•   Substances are made from different types of atoms, which combine with one another in various ways. Atoms form molecules that range in size from two to thousands of atoms.

•   Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it.

•   Gases and liquids are made of molecules or inert atoms that are moving about relative to each other.

•   In a liquid, the molecules are constantly in contact with others; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations.

•   Solids may be formed from molecules, or they may be extended structures with repeating subunits (e.g., crystals).

PS1.B: Chemical Reactions

•   Substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants.

•   The total number of each type of atom is conserved, and thus the mass does not change.

•   Some chemical reactions release energy, others store energy.

Practice 1: Asking questions and defining problems

1A: Ask questions that arise from careful observation of phenomena, models, or unexpected results.

1B: Ask question to identify and/or clarify evidence and/or the premise(s) of an argument.

1E: Ask questions that require sufficient and appropriate empirical evidence to answer.

1F: Ask questions that can be investigated within the scope of the classroom, outdoor environment, and based on observations and scientific principles.

Practice 2: Developing and using models:

2A: Evaluate limitations of a model for a proposed object or tool.

Practice 8: Obtaining, evaluating, and communicating information:

8E: Communicate scientific and/or technical information (e.g. about a proposed object, tool, process, system) in writing and/or through oral presentations.

1. Patterns:

1A: Macroscopic patterns are related to the nature of microscopic and atomic-level structure.

3. Scale, Proportion, and Quantity:

3A: Time, space, and energy phenomena can be observed at various scales using models to study systems that are too large or too small.

3E: Phenomena that can be observed at one scale may not be observable at another scale.

4. Systems and Systems models:

4B: Models can be used to represent systems and their interactions—such as inputs, processes and outputs—and energy, matter, and information flows within systems.

4C: Models are limited in that they only represent certain aspects of the system under study.

5. Energy and Matter:

5A: Matter is conserved because atoms are conserved in physical and chemical processes.

6. Structure and Function

6A: Complex and microscopic structures and systems can be visualized, modeled, and used to describe how their function depends on the shapes, composition, and relationships among its parts; therefore, complex natural and designed structures/systems can be analyzed to determine how they function.

7. Stability and Change:

7A: Explanations of stability and change in natural or designed systems can be constructed by examining the changes over time and forces at different scales, including the atomic scale.