January 24, 2018

Physics: Thermal Energy and States of Matter

Changes of State
Source: dlms6thgradescience.weebly.com

The physical change from one state of matter to another is called a change of state.
The state of a substance depends on the amount of thermal energy it possesses. The more thermal energy a substance has, the faster its particles move.
Matter will change from one state to another if thermal energy is absorbed or released.

Solid-Liquid Changes of State
Source: mstworkbooks.co.za

The change of state from a solid to a liquid is called melting. Melting occurs when a solid absorbs thermal energy. The temperature at which a solid changes to a liquid is called the melting point.

The change of state from a liquid to a solid is called freezing. Freezing occurs when a substance loses thermal energy. The temperature at which a substance changes from a liquid to a solid is called its freezing point. For a given substance, the freezing point and the melting point are the same. The only difference between the two is whether the substance is gaining or releasing thermal energy.

Liquid-Gas Changes of State

Source: mstworkbooks.co.za
The process by which matter changes from the liquid to the gas state is called vaporization. During this process, particles in a liquid absorb thermal energy.
If vaporization takes place at the surface of a liquid, it is called evaporation. At higher temperatures, vaporization can occur below the surface of a liquid as well. This process is called boiling.
The temperature at which a liquid boils is called its boiling point.

A change from the gas state to the liquid state is called condensation.

Thermal Expansion

Source: plumbingsupply.com
As the thermal energy of a substance increases, its particles spread out and the substance expands.
The expanding of matter when it is heated is known as thermal expansion.

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