5-8

E5: Describe how the motion of the particles of matter determines the state of that matter (e.g. solid, liquid, gas, plasma) and vice versa.

Curriculum Organizing Questions	How is the motion of particles in a solid different than the motion of particles in a liquid (or gas or plasma)? How is energy related to the state of matter? How does the state of matter affect the ways its volume and shape can change? Where do you see changes of state happening in your home?
Elaboration	This is the basis of what in grades 9-12 will be developed as the kinetic-molecular model. At this stage focus on how a simple model (moving particles) can explain very concrete, observable behaviors of matter (states of matter). This is very similar to indicator H6 (grades 5-8).
Specific Ideas	Atoms and molecules are perpetually in motion. Increased temperature means greater average energy of motion, so most substances expand when heated. In solids, the atoms are closely locked in position and can only vibrate. In liquids, the atoms or molecules have higher energy, are more loosely connected, and can slide past one another; some molecules may get enough energy to escape into a gas. In gases, the atoms or molecules have still more energy and are free of one another except during occasional collisions. Benchmarks 4D3 By the end of 8th grade, students should be able to read analog and digital meters on instruments used to make direct measurement of temperature. Benchmarks 12C3 Models are often used to think about processes that happen too quickly or on too small a scale to observe directly. Benchmarks 11B1
Developmental &Instructional Implications	This is an excellent place to connect to measurement and calibration of temperature scales. (Preview Committee) Elementary and middle-school students may think everything that exists is matter, including heat, light, and electricity. Alternatively, they may believe that matter does not include liquids and gases or that they are weightless materials. With specially designed instruction, some middle-school students can learn the scientific notion of matter. Benchmarks p. 336 Students of all ages show a wide range of beliefs about the nature and behavior of particles. They lack an appreciation of the very small size of particles; attribute macroscopic properties to particles; believe there must be something in the space between particles; have difficulty in appreciating the intrinsic motion of particles in solids, liquids and gases; and have problems in conceptualizing forces between particles. Despite these difficulties, there is some evidence that carefully designed instruction carried out over a long period of time may help middle-school students develop correct ideas about particles. Atlas p. 58 Students may believe that all substances boil at 100 °C and freeze at 0 °C. Students confuse temperature and state - i.e. the misconception that hot things can't be solids.
Examples	Bimetallic strips in thermostats show expansion of solids with heat.

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