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The website has the complete lesson note for all the subjects in secondary school but this piece showcases the JSS2 Basic Science Lesson Note on Explanation of Melting; Boiling and Evaporation Using Kinetic Theory. You can use the website search button to filter out the subject of interest to you.

CONTENT:Â  EXPLANATION OF, MELTING, BOILING AND EVAPORATION USING KINETIC THEORY

MELTING

When a solid is melting, the particles acquire more kinetic energy and vibrate more vigorously. Eventually, at a certain temperature called the melting point of the solid, the force of the vibration overcomes the binding force and the solid structures collapse. The particles are no longer held in fixed positions but ready to move about. At this point, the solid is said to have melted or liquefied.

Formation of Geysers

Geysers are caused when underground chambers of water are heated to the boiling point by volcanic rock. When heat causes the water to boil, pressure forces a superheated column of steam and water to the surface. Because most geothermal reservoirs are capped by overlying rock, the heated water cannot escape, remaining underground instead. If a geothermal reservoir is sufficiently close to the surface, the heated water can be piped to the surface and used to produce energy.

Geyser

Thundering skyward, a geyser hurls jets of steam and boiling water high into the air. Geysers form when volcanic rocks heat water that is trapped underground to its boiling point. The vapour pressure of the trapped water increases until it is strong enough to push out a column of cooler water above and make the geyser erupt.

BOILING: Boiling is the vaporization of liquid molecules throughout the entire liquid. The temperature at which a liquid changes into vapour is called its boiling point. Substances have different boiling points. Water has a boiling point of 1000C, Ethanol has a boiling point of 780C etc. This happens under normal atmospheric pressure.

When liquid is heated, the molecules of the liquid nearest to the source of heat acquire enough energy to increase their velocities. They move away, to be replaced by other molecules, which soon increase their velocities and move away also. There is a constant movement of more energetic molecules, to be replaced by less energetic molecules. With the continuous supply of heat, molecules with sufficient energy escape from the body of the liquid to form vapour, which exerts its own pressure. At a point, the number of molecules leaving the liquid to form vapour equals that falling back to the liquid. The vapour is said to be saturated. At aparticular temperature, the saturated vapour pressure of the liquid is equal to the atmospheric pressure. The liquid boils at this temperature.

EVAPORATION