3.14:
States of Matter
Matter exists in three main physical forms: solid, liquid, and gas.
All molecules of matter have a specific amount of kinetic energy, which determines their physical state.
The molecules of solids are densely packed with little space around them and have limited movement. This gives solids a definite shape and volume.
Molecules in liquids are bound by strong, attractive forces, leaving little space around them. Yet they have enough energy to move freely, so the liquids can flow.
In gases, the molecules have high kinetic energy, move quickly past each other, and, as a result, have negligible intermolecular forces. With a lot of space around the molecules, gases have low densities making them compressible.
Matter can convert from one state to another as temperature and pressure change.
When the temperature rises, molecules can gain enough kinetic energy to overcome the intermolecular forces and transition to a less ordered state.
When the pressure rises, molecules are pushed closer to each other, increasing the intermolecular forces and changing matter to a more ordered state.
3.14:
States of Matter
Solids, liquids, and gases are the three states of matter commonly found on Earth. A solid is rigid and possesses a definite shape. A liquid flows and takes the shape of its container, except it forms a flat or slightly curved upper surface when acted upon by gravity. Both liquid and solid samples have volumes nearly independent of pressure. A gas takes both the shape and volume of its container.
Scientists have discovered a fourth state of matter, plasma, that occurs naturally in the interiors of stars. A plasma is a gaseous state of matter that contains appreciable numbers of electrically charged particles. The presence of these charged particles imparts unique properties to plasmas that justify their classification as a state of matter distinct from gases. In addition to stars, plasmas are found in some other high-temperature environments (both natural and man-made), such as lightning strikes, certain television screens, and specialized analytical instruments used to detect trace amounts of metals.
Some samples of matter appear to have one or more properties of solids, liquids, and gases simultaneously. This can occur when the sample is composed of many small pieces. For example, we can pour sand as if it were a liquid because it is composed of many small grains of solid sand. Matter can also have properties of more than one state when it is a mixture, such as with clouds. Clouds appear to behave somewhat like gases, but they are mixtures of air (gas) and tiny water particles (liquid or solid).
The differences in the properties of a solid, liquid, or gas reflect the strengths of the attractive forces between the atoms, molecules, or ions that make up each phase. The phase in which a substance exists depends on the relative extents of its intermolecular forces (IMFs) and the kinetic energies (KE) of the molecules. Particles in a solid are tightly packed together and often arranged in a regular pattern. In a liquid, they are close together with no regular arrangement. In a gas, they are far apart with no regular arrangement. Particles in a solid vibrate about fixed positions and do not generally move in relation to one another. In a liquid, they move past each other but remain in constant contact. In a gas, they move independently of one another except when they collide.
This text is adapted from Openstax, Chemistry 2e, Section 1.2: Phases and Classification of Matter and Openstax, Chemistry 2e, Section 10.1: Intermolecular Forces