Melting Point: Process, Experiment, Latent Heat, Advantages

Melting point of a material is the temperature at which it transitions from solid to liquid at atmospheric pressure. These two phases, solid and liquid, are in equilibrium at melting point, which means that both solid and liquid states exist at the same time. A substance's melting point is determined by air pressure. 

The kinetic energy of particles increases as the temperature of solids rises.The particles begin to vibrate at a faster rate as their kinetic energy rises. Heat energy overcomes the forces of attraction that exist between the particles. The particles begin to move more freely once they have left their fixed places. When a solid melts and becomes a liquid, it reaches its melting point.

Process of Melting

[Click Here for Sample Questions]

• Almost all solids are packed or formed in a hard crystal lattice with strong intermolecular attraction forces. When the heat passes, the heat energy overcomes the internal binding energy of the crystal lattice, weakening the intermolecular attraction forces.

Melting Point

• The crystal lattice becomes unstable when the intermolecular forces of attraction lessen. Solid molecules tend to split from one another and begin travelling in opposite directions. The melting of a solid substance is caused by the instability of the crystal lattice.
• According to the widely recognised melting theory, when a substance's temperature rises as a result of heat or increased pressure, the molecules begin to vibrate in their normal positions. When the amplitude (or distance covered) of a vibration exceeds the material's interatomic distance, vibrational instability occurs, causing the substance to melt.

Melting Point

Melting Point Experiment

[Click Here for Sample Questions]

• Fill a half-filled beaker halfway with dry crushed ice made from distilled water.
• Suspend a Celsius thermometer from the clamp stand so that the thermometer's bulb is totally encased in ice.
• After the ice melts and the thermometer reading remains stationary for 2 minutes, read the thermometer reading and record the temperature every 1 minute.
• In the observation table, make a note of the readings.

Also check:

Results

1. Melting point of ice is 0 °C.
2. Once the melting of ice begins the temperature remains constant for some time.

Melting Point Experiment

Precautions

1. A better quality thermometer should be used whose graduated scale is clearly readable.
2. Record the temperature in whole numbers.
3. While reading the thermometer the eye level should be parallel with mercury level.
4. Dip only the bulb of the thermometer into water/ice.
5. The thermometer should not come into contact with the walls of the beaker or the boiling tube.

Also Read: 

Observations

• This experiment helps students comprehend the term "melting point."
• Students conduct the ice cube experiment and observe the physical changes that occur when the ice melts.
• Once students comprehend the different processes, they will be able to complete the experiment faster and more accurately in the real lab.
• When a substance melts at its melting point, students understand that temperature remains constant.

Melting Point of Common Substance

[Click Here for Sample Questions]

Latent Heat of Fusion

[Click Here for Sample Questions]

Ice has a melting point of 273.15 K*. Melting, or the transition from a solid to a liquid state, is also known as fusion. Because the temperature of a solid does not change when it melts, where does the heat energy go?

• During the melting experiment, you must have seen that after the melting point is achieved, the temperature of the system does not change until all of the ice has melted.
• This occurs despite the fact that we continue to heat the beaker, i.e., we continue to deliver heat. By overcoming the forces of attraction between the particles, this heat is utilised to change the state. Because this thermal energy is absorbed by ice without causing a temperature rise, it is thought to be concealed in the contents of the beaker and is referred to as latent heat. Something that is hidden is referred to as "latent."The latent heat of fusion is the amount of heat energy necessary to convert 1 kg of a solid into a liquid under atmospheric pressure at its melting point.
• As a result, particles in water at 0 C (273 K) have more energy than those in ice at the same temperature.
• Other than changes in a given element's solid, liquid, or vapour states, latent heat is associated with operations. Almost all solids exist in a variety of crystalline forms, and the changes between them almost always include the absorption or evolution of latent heat.

Latent Heat of Fusion

Melting Point: Advantage

[Click Here for Sample Questions]

• Melting point of a substance aids in the identification of that substance. The purity of a substance can also be determined by measuring the melting point of a solid. Melting point of a combination is less than that of a pure solid. Pure crystalline substances melt over a very small temperature range, whereas mixtures melt over a much wider range.
• The freezing point, also known as the crystallisation point, is the temperature at which a liquid transforms into a solid. Most substances have the same melting and freezing points.
• Ice has a melting point of 0°C or 273K. Tungsten (3410°C) is the chemical element with the highest melting point, and it is used to make light bulb filaments.
• The temperature of the system does not increase until after the melting point is achieved during the melting process, until all of the ice has melted. The entire amount of heat energy given is used to increase the ice molecules' potential energy. So long as the melting continues, the molecule's kinetic energy does not increase, and the temperature does not rise.

Also Read: 

Things to Remember

[Click Here for Sample Questions]

• Melting Point is the temperature at which any substance transitions from solid state to liquid state at normal atmospheric pressure.
• Solid state and liquid state are in equilibrium at this time meaning that both the states exist at the same time. 
• Heat causes previously static molecules to move faster until they start breaking apart. This causes a solid substance to transform into a liquid.
• Melting point has an advantage that it allows to check the purity of a substance as different elements have different melting points. 

Read More :