Have you ever noticed how ice melts into water or how water turns into streams when heated?

These changes happen at specific temperatures called the melting point and boiling point. Understanding these points is important. They will help us know how a substance behaves when heated or cooled. In this article, we’ll explore what melting and boiling points are, how they are different, how we measure them, and what factors can change them. Whether you’re preparing for an exam or just curious, this guide will make it all easy to understand. 

Melting and Boiling Point

Melting point: The temperature at which a substance transitions from a solid to a liquid state is known as its melting point. The solid and liquid phases are in equilibrium at the melting point. A solid's temperature rises when heat is added to it until it reaches the melting point. Pressure also affects melting point, typically reported at a standard pressure such as 1 atmosphere or 100 kPa. 

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A liquid's boiling point changes depending on the pressure being applied, which is the average atmospheric pressure at sea level (760 mm [29.92 inches] of mercury). Water boils at sea level at 100° C (212° F). Therefore, lower boiling point temperatures are observed at greater altitudes.

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• Boiling point: The temperature at which a liquid's vapor pressure equals the pressure around it and the liquid transforms into a vapor is known as the boiling point of a substance. At this temperature, adding heat causes the liquid to turn into its vapor without raising the temperature. 
• Freezing Point: The freezing point of a liquid is the temperature at which it turns into a solid. Similar to the melting point, the freezing point typically rises with increasing pressure. In the case of mixtures and for some organic substances, such as lipids, the freezing point is lower than the melting point.

The key differences between the melting and boiling point are discussed in the table below: 

How are Boiling and Melting Points Determined?

Melting and boiling points are usually found through simple lab methods. To check the melting point, a small amount of the solid is heated slowly, and the temperature at which it starts turning into a liquid is noted. For boiling points, a liquid is heated until it starts forming bubbles and changes into gas. Tools like a thermometer and heating setup are used to measure the exact temperature. These values help identify substances and check their purity as pure materials have sharp and fixed melting or boiling points.

Factors affecting the Boiling and Melting point?

The melting and boiling points of a substance can change due to important factors. First, stronger forces between particles (like hydrogen bonds or ionic bonds) usually lead to higher melting and boiling points. Second, the size and shape of molecules matter; bigger or heavier molecules often need more heat. Third, if there are impurities, they can either lower the melting point or raise the boiling point. Lastly, pressure plays a key role, especially for boiling. For example, water boils at a lower temperature in hill stations because the air pressure is lower.

Real Life Applications and Experiences

Knowing the melting and boiling points of substance is useful in everyday life and in science. In the kitchen, we see these changes while boiling water or melting butter. In labs, these points help identify unknown substances or check how pure they are. Industries like food, medicine, and cosmetics rely on this information to make sure products are made safely and work properly. Even weather and altitude can affect boiling points, which is why cooking instructions sometimes vary by location.

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