Ch. 2 - Solids, Liquids, and Gasses
Standards covered in this chapter:
7.PS1.6 - Create and interpret models of substances whose atoms represent the states of matter with respect to temperature and pressure.
Important Vocabulary:
Solid - has a definite shape and a definite volume.
Liquid - has a definite volume but no shape of its own.
Gas - has neither a definite shape nor a definite volume.
Surface Tension - an inward force, or pull, among the molecules in a liquid that brings the molecules on the surface closer together.
Viscosity - a liquid's resistance to flowing.
Pressure - the force pushing on a surface divided by the area of that surface.
Melting - the change in state from a solid to a liquid.
Freezing - the change in state from a liquid to a solid.
Vaporization - the change in state from a liquid to a gas.
Evaporation - the process by which molecules at the surface of a liquid absorb enough energy to change to a gas.
Summary
The fixed, closely packed arrangement of particles causes a solid to have a definite shape and volume. A liquid has no definite shape but it has a definite volume because its particles are free to move. As gas particles move, they spread apart, filling all the space available. Therefore, a gas has neither a definite shape, nor a definite volume. At a solid's melting point, particles vibrate so fast that they break free from their fixed positions. Vaporization occurs when particles in a liquid gain enough thermal energy to move independently. When the temperature of a gas at a constant pressure is increased, its volume increases.
Particles in a solid are packed closely together. A solid has a definite shape and a definite volume.
Particles in a liquid are free to move so a liquid has no shape of its own, but it does have a definite volume.
