Determination of Melting Point
Melting point of a substance is a temperature at which vapor pressure of the substance is equal to the atmospheric pressure. The principle and method of determination of melting point are discussed below.
Principle of Determination of Melting Point
During the process of melting, all the energy is provided to a substance as the heat of fusion and temperature of the substance remains constant. A pure crystalline substance has a sharply defined melting point. Pure substance becomes clear and transparent when it reaches its melting point.
A capillary tube melting point, which is also known as complete melting point is a temperature at which a heated substance becomes a clear liquid and the lower end of the capillary tube.
Method of Determination of Melting Point
The determination of melting point can take place via capillary tube method. In this method a thermometer, capillary tube and the sample to be tested is required. The procedure of the capillary tube method is described below:
Step 1: A small amount of sample substance is grounded in a rotating motor.
Step 2: This homogeneous powered substance is then dried in a desiccator using a drying agent such as Phosphorous Pentaoxide.
Step 3: The capillary tube is then filled with sample substance with height between 2mm to 3mm.
Step 4: Heat the apparatus till it reaches the temperature 5-10°C and then lower the temperature such that the temperature of the apparatus rises about 1°C/minute.
Step 5: When the sampled substance is changed into a clear transparent liquid, note that reading of thermometer.
The noted temperature at which the sample substance became a clear transparent liquid is the melting point of the substance. Thus, there is complete disappearance of solid phase of the substance, and it is changed to complete transparent liquid.
Melting point is thus determined by the capillary tube method as the temperature when the substance has just completely melted.
Melting and Boiling Point
Melting and Boiling Point of a substance are the temperatures at which the state of matter changes from solid to liquid and liquid to gas respectively. These two temperature points are important to understand the physical properties of matter.
In this article, we will learn about the melting point, boiling point definition, their characteristics, factors affecting them, and boiling and melting point of some commonly known elements.
Table of Content
- What is Melting Point?
- What is Boiling Point?
- Examples of Melting and Boiling Point
- Melting and Boiling Points of Various Elements
- Factors Affecting Melting and Boiling Point
- Difference between Melting and Boiling Point