What are the two ways in which the physical states of matter can be changed?

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melting and boiling

By heating and cooling

The physical states of matter can be changed through two processes known as phase transitions or phase changes. The two ways in which the physical states of matter can be changed are:

1. Heating or adding energy: When matter is heated or energy is added to it, the average kinetic energy of its particles increases. This increase in energy causes the particles to move faster and overcome the intermolecular forces that hold them together. As a result, the substance undergoes a phase change from a solid to a liquid, or from a liquid to a gas. This process is known as melting (solid to liquid) or evaporation/vaporization (liquid to gas).

2. Cooling or removing energy: Conversely, when matter is cooled or energy is removed from it, the average kinetic energy of its particles decreases. This reduction in energy weakens the intermolecular forces between the particles, causing them to slow down and move closer together. Consequently, the substance undergoes a phase change from a gas to a liquid, or from a liquid to a solid. This process is called condensation (gas to liquid) or freezing/solidification (liquid to solid).

It is important to note that these phase changes occur at specific temperatures known as melting point, boiling point, condensation point, and freezing point. The exact temperatures depend on the substance being transformed. One can determine the specific phase changes and their corresponding temperatures for a given substance by referring to a phase diagram or conducting experiments.