Heat of fusion, also called the specific latent heat of a substance, is the amount of heat energy provided to one gram of substance that changes its state from a solid to a liquid keeping pressure constant.
For example, If we want to change ice to water, a specific amount of heat is required which will be dependent upon the heat of fusion of ice and the amount of water present.
The Heat of fusion is denoted by Δl
The heat of fusion formula is given as
q = m·Δl
where
q is heat energy
m is mass
ΔHf is the heat of fusion
Example:
Find the amount of heat needed to melt 200gms of ice, if the heat of fusion of ice is 330 J/gm
Ans:
Mass of ice(m) = 200gm
Heat of fusion(Δl) = 330 J/gm
Heat needed(q) = m.Δl
= 200 x 330
=66000J or 6.6 x 104 J.
Applications of Heat of Fusion
The applications related to the heat of fusion can be seen very commonly in our daily life around us. Many of the popular household products are created using the heat of the fusion process, which can be seen in a variety of applications. The most common and easy example of use of the heat of fusion is the melting of ice into water form. The manufacturing industries are home to the many great majorities of examples of the heat of fusion that are in use. The following examples have been worked upon to make them perfect over hundreds of years and are still being worked on to be used today. The heat of fusion is a major requirement to perform the operation of coin production, glassblowing, forging metal items, and even in transforming blow moulded polymers into household products. The plastic Coke bottle from the vending machine, the change in your pocket, and the vase of glass on a fireplace mantle all have been created and went through a heat of fusion manufacturing process.
Copper and Solid Zinc, which are also the metals used in American pennies, are heated at a high temperature in a casting furnace until they attain the liquid phase using the heat of fusion method. The molten zinc and copper are then poured into a mould and are moulded into the shape of long bars once they have reached their liquid phase. The molten metal transforms from its liquid form to a solid-state throughout this process of casting, resulting in a solid bar. Heavy machinery is used which helps in flattening these long bars, which are then stamped over and are shaped into thousands of coins. A monetary system would not be easy and could not exist in the United States without the process of heat of fusion.
Concept of Heat of Fusion
The concept of heat of fusion can be understood as when the amount of energy required to melt a given quantity of a solid at its melting point temperature is measured by heat of fusion. In the other Words, when a certain mass of liquid transforms and solidifies, it also indicates the amount of energy lost during this. For example, we can see that water has a fusion heat of around 80 calories per gram. This means that it consumes 80 calories of energy to melt 1 gram of ice at the temperature of zero degrees Celsius into water. The value of heat of fusion can vary here depending upon what type of substance is being used.
We can see that the heat received by ice is equal to the heat lost by water, for example. The heat of fusion is represented by the symbol ΔHf.
Melting is the process through which a solid material transforms into a liquid. To allow the solid-state particles to break loose from one other, the melting process will require an increase in energy. Fusion heat is the source of this energy. Although the heat of fusion is not the same for all substances, it is a constant value for each type of substance.