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Melting and Boiling Points

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Last updated date: 02nd Mar 2024
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Overview of Boiling Melting Points

Kids, imagine there is a Girl named Anna who went on a summer vacation with her family to the Maldives. The weather was extremely hot so Anna asked her mum to make her some ice cream. She then took her ice cream and went into the park in the hot sun. Anna noticed that the ice cream started to melt. What did we learn from this? we learned the concept of melting. 


Melting is a point where a solid substance turns into a liquid when heated. Imagine there is a grandma who keeps water to boil on the stove. After a few minutes, grandma notices vapour coming out from the bowl. Boling is a point when a liquid starts to boil when heated. Let's further understand the concept of melting and boiling point in this article.


Melting of Ice Cream and Boiling of Water



Melting of Ice Cream and Boiling of Water


What is the Boiling Point of Water?

The Boiling point of water is 100 ° C  Or 212 ° F. The value does not remain the same; it depends on the open atmospheric pressure. This pressure changes according to changes in the heat. If you increase the temperature by applying more heat to the container then the temperature rises. If you then lower the heat pressure then the atmospheric pressure reduces leading to a lower temperature.



Similarly, the quality of the water also affects its boiling point. The boiling point of impure water (such as salty water) is higher than that of clean water. We refer to this as a rise in the boiling point or elevation.


Example of Increase in Boiling Point

We use a pressure cooker for cooking food because it utilizes less time to cook food. It is one of the most common examples of a Boiling point. When we place water into the cooker and let it boil after a few minutes we see the vapour coming out from the cooker through the whistles. This is because when we apply heat the temperature rises to lead to vapour trapping which further leads to increased pressure in the cooker that is why cooking gets faster using a cooker.


Pressure Releasing From Cooker


Pressure Releasing From Cooker


What is the Melting Point of Water?

Melting point refers to the transformation of a solid into a liquid. Adding heat to a solid cause it to melt. By doing this, the particle's molecules become more active and start to vibrate. As a result of all this jiggling around, the molecules in the material are unable to cling to one another as tenaciously as they do in the solid phase; consequently, they separate, and the substance transitions to the liquid state. 


The temperature at which water transforms from solid ice to liquid water is known as the melting point. At this temperature, the solid and liquid states of water are equal. There isn't a single temperature that can be regarded as the melting point of water because the melting point partly depends on pressure. However, for practical purposes, 0°C, or 32 °F or 273.15 K, is quite close to being the melting point of pure water ice at 1 atmosphere of pressure.


How does Melting Happen?

To melt a substance, heat can be applied slowly or rapidly. We simply have to transfer the ice cubes from a cooler to a warmer setting; this will result in the melting of the ice water present in the glass. This process can take longer if we place the ice water glass in the refrigerator as the temperature inside is lower when compared to the kitchen counter. However, if we had placed the glass and ice cubes in a hot oven, the ice would just have melted considerably more quickly due to the significantly higher temperature of the oven compared to the kitchen. Apart from this melting point of water also depends on the substance itself to understand this let's take an example.


Example of Melting Point

Let us say there are 2 different substances frozen at -25 degrees in the refrigerator. The first glass contains water and the second glass contains olive oil. At -25 degrees both these substances are solid. If we turn the refrigerator off the olive oil starts melting at 20 degrees Celsius. But the ice remains the same. As we increase the temperature to 0°C the ice starts to melt. This means that the melting point of water is 0°C Why did this happen? It is because different substances require different levels of heat to melt. Some substances like aluminium require a heat level of 660°C to melt while silver requires 1550° C to melt.


Difference Between Melting and Boiling Point

The differences are as follows:

Particulars

Melting Point

Boiling Point 

Definition 

Melting is the temperature at which the solid turn into liquid

The temperature at which the vapour pressure of the liquid becomes equal to atmospheric or external pressure is called the boiling point.

Process

A solid-state turns into liquid

A liquid state turns into gas

Vapour Pressure 

No relation with the vapour pressure

The pressure equals the pressure of the surrounding 

Example

The melting point of water is 0°C

The Boiling point of water is 100° C


Summary 

In this article, we learned that a boiling point is a temperature at which the vapour pressure is equal to the surrounding pressure. We learned how the surrounding pressure and vapour pressure are proportionate. Through the example of a pressure cooker, we learned the concept of boiling point. Further, we got to know about the Boiling point of water and how temperature varies as per the applied Pressure. Further, we learned about a melting point which is the temperature at which the solid turns into liquid, and how melting depends upon the temperature at which the substance is kept. We hope you enjoyed reading this article, in case of any other doubts, feel free to ask in the comments.

FAQs on Melting and Boiling Points

1. What are the four transitions of substances?

The phase change from solid to liquid is called melting. The phase change from liquid to solid is known as freezing. The process by which a liquid changes into a gas is called evaporation. The process by which a gas changes into a liquid is called condensation.

2. When comparing freezing point to melting point, what is the difference?

At atmospheric pressure, a liquid's freezing point is the temperature at which it solidifies. As an alternative definition, a melting point is a temperature at which solid changes into a liquid under standard atmospheric pressure.

3. Does the Air freeze?

The answer is "yes"; air can freeze. The percentages of oxygen, nitrogen, and argon in the air are 21, and 78,1 °C respective. Argon freezes at -308.7 degrees Fahrenheit, while nitrogen and oxygen both freeze at -346.18 degrees. If the temperature drops low enough, oxygen in the air will freeze solid. The Earth never reaches those temperatures on its own.