States of Matter
Area
Sciences
Duration
1 session
Dimension of the advised group of students
unlimited
Specific objectives
-Describe a molecular model for solids, liquids and gases.
-Extend this model to phase changes.
-Describe how heating or cooling changes the behavior of molecules.
-Describe how a change in volume can affect temperature, pressure, and state.
-Relate a pressure-temperature diagram to the behavior of molecules.
Needed Materials
Computers or laptops
Internet connection
Software
The activities are online.
Description
The PHET simulation from the University of Colorado shows what happens at the microscopic level during changes in physical states by changing the
temperature and pressure.
Procedure on how to put in practice
The explanation for the differences between solids, liquids and gases lies in the way their molecules move. In a gas, the molecules are in constant and random motion in a large empty volume; in a liquid, the molecules move freely, but are very close together, leaving little empty volume. Thus, they can flow but cannot be compressed since the empty volume is minimal. Finally, solids are composed of particles which are in fixed positions and cannot move so they cannot be compressed and flow.
Solids retain their shape, unlike fluids (gases and liquids) which flow easily and occupy the container in which they are placed. Liquids do not compress, unlike gases which can be compressed. Rigidity and compressibility are the properties that separate solids, liquids and gases.
What phenomena of melting, liquefaction, coagulation, sublimation do you encounter in your daily life?
