Thermal Energy: Hot vs Cold
- Thermal Energy: Total kinetic energy of the individual particles in an object. (more mass = more energy)
- Temperature: The AVERAGE kinetic energy of the particles in an object.
- "Hot": More thermal energy (particles vibrate more)
- "Cold" : Less thermal energy (particles vibrate less)
Kinetic Model of Matter - States of Matter
Gases
- A collection of widely separated molecules
- The kinetic energy of the molecules is greater than any attractive forces between the molecules
- The lack of any significant attractive force between molecules allows a gas to expand to fill its container
- If attractive forces become large enough, then the gases exhibit non-ideal behavior
Liquids
- The intermolecular attractive forces are strong enough to hold molecules close together
- Liquids are more dense and less compressible than gasses
- Liquids have a definite volume, independent of the size and shape of their container
- The attractive forces are not strong enough, however, to keep neighboring molecules in a fixed position and molecules are free to move past or slide over one another
Solids
- The intermolecular forces between neighboring molecules are strong enough to keep them locked in position
- Solids (like liquids) are not very compressible due to the lack of space between molecules
- If the molecules in a solid adopt a highly ordered packing arrangement, the structures are said to be crystalline
The state of a substance depends on the balance between the kinetic energy of the individual particles (molecules or atoms) and the intermolecular forces
- Kinetic energy keeps the molecules apart and moving around, and is a function of the temperature of the substance
- Intermolecular forces try to draw the particles together
Gases have weaker intermolecular forces than liquids
Liquids have weaker intermolecular forces than solids
Expansion & Contraction