Final answer:
The kinetic theory explains the differences between states of matter based on particle motion and energy. It describes how particles behave in solids, liquids, and gases, and correlates temperature with particle kinetic energy.
Step-by-step explanation:
The kinetic theory is an important concept in physics that helps explain the differences between states of matter (solid, liquid, and gas) and the behaviors of particles in these states. It states that all matter is made up of particles which are in constant motion; the extent of this motion depends on the energy (or temperature) of the particles. As the temperature increases, particles move faster, which can lead to changes in the state of matter.
In a solid, the particles vibrate around fixed positions due to low kinetic energy. In a liquid, the particles have more energy and can move more freely around each other, while maintaining close contact. In a gas, the particles have enough kinetic energy to overcome attractive forces substantially, moving freely and rapidly in all directions.
According to the kinetic-molecular theory, temperature is directly proportional to the average kinetic energy of the particles in a substance. So, if we increase the temperature, the average speed and kinetic energy of the particles also increase. This relationship helps explain why water exists in different states (ice, liquid water, water vapor) under different temperature conditions.
Therefore answer is 2) states of matter.