Thermal Energy and States of Matter

Jacques Charles ( $1746-1823$ ): A French scientist who established the relationship between the temperature and volume of a gas.
Charles’s Law: States that the volume of a gas increases as temperature increases, provided the pressure remains constant.
Thermal Contraction: A decrease in volume that occurs when the temperature of a substance decreases.
Thermal Expansion: An increase in volume that occurs when the temperature of a substance increases.
Particle Interaction: When thermal energy changes, the size of individual particles remains the same; however, the space between the particles changes, altering the total volume.

Heat: The transfer of thermal energy from a region of higher temperature to a region of lower temperature.
Heating Process: Occurs when thermal energy transfers between objects in contact, which can be solids, liquids, or gases.
Open System: A system where energy is released into the surrounding environment.
Closed System: A theoretical model used by scientists where no matter or energy is exchanged between the system and its environment.

Pressure Definition: The amount of force applied per unit of area on a surface ( $\text{Pressure} = \frac{\text{Force}}{\text{Area}}$ ).
Cause of Pressure: Resulting from gas particles colliding with the walls of their container.
Units of Pressure: Often measured in atmospheres ( $atm$ ), where the pressure at sea level is exactly $1\,atm$ .
Temperature Impact:
- Decreasing temperature causes particles to slow down, leading to fewer collisions and lower pressure.
- Increasing thermal energy speeds up particle motion, resulting in more frequent collisions and higher pressure.

Melting: The transition from solid to liquid. At the melting point, temperature remains constant while particles overcome attractive forces and potential energy increases.
Vaporization: The transition from liquid to gas.
- Boiling: Vaporization occurring throughout the entire liquid at a specific boiling point.
- Evaporation: Vaporization occurring only at the surface of a liquid; particles must overcome the force of air pressure to escape into the air.
Freezing: The transition from liquid to solid. The freezing point of a substance is identical to its melting point. Temperature remains constant during the transition until the liquid is fully solidified.
Condensation: The process where a gas loses enough thermal energy to change into a liquid.

Statement: Thermal energy moves from cooler objects to warmer objects.
Response: Disagree. Thermal energy (heat) naturally transfers from regions of higher temperature to lower temperature.
Statement: A change in temperature can change the volume of a gas.
Response: Agree. According to Charles's Law, changing the temperature of a gas directly affects its volume if pressure is constant.