por We explain what melting is in chemistry, the melting point, and we give many examples.
What is fusion in chemistry?
The fusion It is a phase change in which a substance in the solid state changes to the liquid state. In other words, fusion is the technical name for the process that occurs when a solid melts.
The fusion process is a particular type of physical changesince when a solid substance melts, it remains the same chemicalonly in a new state or in a different phase than the previous one.
For example, ice is a solid substance made up of water molecules (H₂O). If we melt ice, we get liquid water, which is made up of the same water molecules. That is, no chemical change occurs in the substance, only a physical change.
The melting process can be represented in a similar way to a chemical reaction, by means of an equation such as the following:
Where A represents the molecular or empirical formula of the substance, (s) indicates the solid state and (l) the liquid state. The two arrows indicate that the fusion is reversible. This means that the opposite process can occur (the transition from liquid to solid), which is called solidification.
melting point
Fusion occurs when we increase the temperature of a body up to a certain value. This happens because the temperature causes the molecules shake with more and more force, until they manage to break the forces that hold them together in the solid.
The temperature at which a substance melts is called melting point or melting temperature (Tfus). This temperature varies slightly with atmospheric pressure. When the melting point is measured at a pressure of 1 atm, it is called the normal melting point.
The temperature at which a solid melts also depends on its composition, since each substance has a characteristic melting point. For example, the normal melting point of ice is 0 °C, while iron melts at 1,538 °C.
Fusion Examples
melting ice
Ice is nothing more than solid water. At a pressure of 1 atm, ice melts at 0 °C thus becoming liquid water.
Fusion of welds
When mixed in very specific proportions, some metals form mixtures called eutectic materials, which melt at low temperatures making them useful for use as low-temperature solder.
lead melting
Unlike metals like iron, which melt at over 1,500°C, lead melts at only 327.5°C.
sugar melting
Many of us have seen how caramel is made by melting sugar. This melts around 186 °C. However, it also decomposes at this temperature, transforming into different dark-colored substances with a characteristic caramel odor.
galinstan fusion
Galinstan is a eutectic made up of gallium, indium and tin that melts at –19°C, making it a liquid at room temperature. It is less toxic than mercury, which is why it is used as a substitute in the manufacture of thermometers.
sand fusion
The sand is made up mainly of minerals such as quartz (silica) and alumina. The sand is melted and then solidified to make glass. The sand melts at approximately 1,700 °C.
rock melting
Rocks melt in the center of the earth due to the high temperatures and pressures found there, turning into the bright orange magma we see in volcanic eruptions.
paraffin melting
The melting of the paraffin with which candles are made is another example of a melting process that we can easily see in our homes. Most candles melt between 46-68°C.
Fusion of pure copper
Copper is another example of a metal that melts at a high temperature, specifically 1,085°C.
Fusion of copper alloys
The mixture of copper with other metals to produce alloys such as bronze and brass causes its melting temperature to drop to approximately 900 °C.
Frozen
The ice cream melts or melts because the ice exceeds its melting point, the air begins to escape, and the liquid ends up dragging the rest of its components.
In the kitchen
Butters, chocolates, chewing gum and other sweets melt if they receive direct heat from the sun, or if they are enclosed in hot spaces.
icebergs
Icebergs are masses of ice that break off from glaciers and whose ice melts.
Melting Points of Common Substances
A series of common substances with their respective melting points are listed below:
-Ice, 0ºC
-Paraffin, 65.6ºC
-Chocolates, 15.6-36.1ºC (note that it is a range of temperatures, because there are chocolates that melt at lower or higher temperatures)
-Palmitic acid, 63ºC
-Agar, 85ºC
-Phosphorus, 44ºC
-Aluminum, 658ºC
-Calcium, 851ºC
-Gold, 1083ºC
-Copper, 1083ºC
-Iron, 1530ºC
–Mercury, -39ºC (it is liquid at room temperature)
-Methane gas, -182ºC
-Ethanol, -117ºC
-Graphite carbon, 4073ºC
-Diamond carbon, 4096ºC
References
Connor, N. Galistan | Density, Melting Point, Thermal Conductivity. Taken from material-properties.org
RotoMetals. (nd). Low Melt/Fusible Alloys. Taken from rotometals.com