Scope, Sequence, and Coordination

A Framework for High School Science Education

Based on the National Science Education Standards

Understanding the Behavior of Gases

Solids, Liquids, and Gases: Empirical Laws and the Kinetic Theory
Solids, liquids, and gases differ in the distances and angles between molecules or atoms and therefore the energy that binds them together. In solids the structure is nearly rigid; in liquids molecules or atoms move around each other but do not move apart; and in gases molecules or atoms move almost independently of each other and are mostly far apart.

Further Description:

The states of substances can be distinguished by differences in density and compressibility and by changes in volume as a function of temperature. For gases, quantitative empirical relationships can be established among the number of particles present, the masses of these particles, and the density and volume they occupy at standard and nonstandard conditions, thereby relating temperature, pressure, and volume.

These empirical relationships can be explained in terms of the particulate nature of matter, the forces of interaction between particles of matter, and Newton’s laws of motion, leading to a connection between average kinetic energy of molecules and absolute temperature.

Concepts Needed:

Grade 9

Solid, liquid, gas, density, temperature, absolute temperature, constant pressure, volume

Grade 10

Velocity, kinetic energy, pressure, standard pressure

Grade 11

Ideal gas, compressibility

Grade 12

Particles, partial pressure, mass-volume, STP

Empirical Laws or Observed Relationships:

Boyle=s law, Charles= law, Gay-Lussac=s law, universal gas law, Dalton=s law of partial pressures, Graham=s law of diffusion

Theories or Models:

Kinetic molecular theory, Avogadro=s hypothesis, equipartition of energy

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Micro-Unit Description:

Understanding the Behavior of Gases
Students should use the combined gas law to determine changes in volume, pressure, and temperature when two variables are held constant.

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