States of Matter
There are four observable states of matter in nature. They are classified as solid, liquid, gas, and plasma. These substances can transform into each other, and this is the change of state of matter. For example, water can turn into a solid by freezing from liquid matter. Or it can evaporate when water boils. Melting, freezing, evaporation, condensation, sublimation and deposition are the main forms of change of state of matter.
The transformation of solids into liquids by heating is called melting. The temperature remains constant during the melting of the solid, and it is called the melting point.
⇒⇒ The melting point of ice is 0 °C. The melting point is a distinguishing feature of the substance.
Melting examples: melting of ice, snow, chocolate, glass, plastic, and metals such as iron, copper, and gold.
The transformation of a pure substance from liquid to solid is called freezing. The temperature at which freezing occurs is called the freezing point.
Metals such as gold and iron are melted, poured into various molds, and then frozen and shaped. Thus, materials such as plastic, glass, iron, and copper can be recycled and reused.
The conversion of liquids to gas by heating is called evaporation, which takes place only at the surface of the liquid. Evaporation takes place at any temperature. However, as the temperature increases, evaporation also increases.
⇒⇒ We feel cold when our clothes are wet because the water absorbs heat from us as it evaporates.
Evaporation examples: evaporation of water, alcohol, cologne, mercury, gasoline, and diesel
The conversion of gaseous matter to liquid is called condensation. During condensation, the substance gives off heat.
Rain from the cloud, fog formation, dew on the grass in the morning, and condensation on the windows in cold weather are all caused by condensation.
Condensation examples: fogging of window glass and vehicle windows in winter
The transformation of a solid into a gas by heating is called sublimation. Naphthalene, iodine, and dry ice (solid carbon dioxide) sublime and go directly from solid to the gaseous state.