Light & Molecules

Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials.

• 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).
• The changes of state that occur with variations in temperature or pressure can be described and predicted using these models of matter.

• A simple wave has a repeating pattern with a specific wavelength, frequency, and amplitude.
• A sound wave needs a medium through which it is transmitted.

• When light shines on an object, it is reflected, absorbed, or transmitted through the object, depending on the object’s material and the frequency (color) of the light.
• The path that light travels can be traced as straight lines, except at surfaces between different transparent materials (e.g., air and water, air and glass) where the light path bends.
• A wave model of light is useful for explaining brightness, color, and the frequency-dependent bending of light at a surface between media.
• However, because light can travel through space, it cannot be a matter wave, like sound or water waves.

• Develop and use a model to describe phenomena.
• Develop a model to describe unobservable mechanisms.
• Develop a model to generate data to test ideas about designed systems, including those representing inputs and outputs.
• Develop a model to predict and/or describe phenomena.

• Collect data to produce data to serve as the basis for evidence to answer scientific questions or test design solutions under a range of conditions.
• Plan an investigation individually and collaboratively, and in the design: identify independent and dependent variables and controls, what tools are needed to do the gathering, how measurements will be recorded, and how many data are needed to support a claim.
• Conduct an investigation and evaluate the experimental design to produce data to serve as the basis for evidence that can meet the goals of the investigation.

• Cause and effect relationships may be used to predict phenomena in natural or designed systems.
• Relationships can be classified as causal or correlational, and correlation does not necessarily imply causation.
• Phenomena may have more than one cause, and some cause and effect relationships in systems can only be described using probability.

• 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 structures/systems can be analyzed to determine how they function.
• Structures can be designed to serve particular functions by taking into account properties of different materials, and how materials can be shaped and used.

Evaluate the validity and reliability of claims in published materials of the effects that different frequencies of electromagnetic radiation have when absorbed by matter.

• Each atom has a charged substructure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons.
• The periodic table orders elements horizontally by the number of protons in the atom’s nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron states.
• The structure and interactions of matter at the bulk scale are determined by electrical forces within and between atoms.
• A stable molecule has less energy than the same set of atoms separated; one must provide at least this energy in order to take the molecule apart.

• Geologists use seismic waves and their reflection at interfaces between layers to probe structures deep in the planet.
• The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing.
• Information can be digitized (e.g., a picture stored as the values of an array of pixels); in this form, it can be stored reliably in computer memory and sent over long distances as a series of wave pulses.
• [From the 3–5 grade band endpoints] Waves can add or cancel one another as they cross, depending on their relative phase (i.e., relative position of peaks and troughs of the waves), but they emerge unaffected by each other. (Boundary: The discussion at this grade level is qualitative only; it can be based on the fact that two different sounds can pass a location in different directions without getting mixed up.)

• Atoms of each element emit and absorb characteristic frequencies of light. These characteristics allow identification of the presence of an element, even in microscopic quantities.
• Electromagnetic radiation (e.g., radio, microwaves, light) can be modeled as a wave of changing electric and magnetic fields or as particles called photons. The wave model is useful for explaining many features of electromagnetic radiation, and the particle model explains other features.
• When light or longer wavelength electromagnetic radiation is absorbed in matter, it is generally converted into thermal energy (heat). Shorter wavelength electromagnetic radiation (ultraviolet, X-rays, gamma rays) can ionize atoms and cause damage to living cells.
• Photoelectric materials emit electrons when they absorb light of a high-enough frequency.

• Use a model to provide mechanistic accounts of phenomena.
• Develop and use a model based on evidence to illustrate the relationships between systems or between components of a system.
• Use a model to predict the relationships between systems or between components of a system.

• Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly.
• Science investigations use diverse methods and do not always use the same set of procedures to obtain data.
• New technologies advance scientific knowledge.
• Scientific inquiry is characterized by a common set of values that include: logical thinking, precision, open-mindedness, objectivity, skepticism, replicability of results, and honest and ethical reporting of findings.

• Empirical evidence is required to differentiate between cause and correlation and make claims about specific causes and effects.
• Systems can be designed to cause a desired effect.
• Cause and effect relationships can be suggested and predicted for complex natural and human designed systems by examining what is known about smaller scale mechanisms within the system.

• The functions and properties of natural and designed objects and systems can be inferred from their overall structure, the way their components are shaped and used, and the molecular substructures of its various materials.
• Investigating or designing new systems or structures requires a detailed examination of the properties of different materials, the structures of different components, and connections of components to reveal its function and/or solve a problem.