CHANGES OF STATE OF MATTER

Introduction

Matter can exist in three states: solid, liquid, and gas. These states of matter depend on the temperature and pressure of the substance. The changes of state of matter are the processes by which a substance can change from one state to another. There are four main processes of changing state:

1. Melting: This is the process by which a solid changes to a liquid when heat is applied. The temperature at which a substance melts is called its melting point.
2. Freezing: This is the process by which a liquid changes to a solid when it is cooled. The temperature at which a substance freezes is called its freezing point.
3. Vaporization: This is the process by which a liquid changes to a gas when heat is applied. There are two types of vaporization: evaporation, which occurs at the surface of a liquid, and boiling, which occurs throughout the liquid.
4. Condensation: This is the process by which a gas changes to a liquid when it is cooled. This process is the reverse of vaporization.

These changes of state can be represented on a phase diagram, which is a graphical representation of the temperature and pressure at which a substance exists in different states. The point where all three states of matter coexist is called the triple point.

 

Changes of state of matter can be explained in terms of the movement of particles.

The three common states of matter are solid, liquid, and gas. The state of matter depends on the amount of energy the particles possess and the strength of the intermolecular forces between them.

In a solid, the particles are tightly packed together and have very little energy, so they vibrate in place. When energy is added to the solid, the particles begin to move faster and vibrate more, eventually breaking free from their fixed positions and becoming a liquid.

In a liquid, the particles have more energy than in a solid and are free to move around but still have some intermolecular forces holding them together. When energy is added to the liquid, the particles move even faster, and the intermolecular forces weaken until they can no longer hold the liquid together, and it becomes a gas.

In a gas, the particles have the most energy and are free to move independently of each other. When energy is removed from the gas, the particles move more slowly, and the intermolecular forces between them become strong enough to cause them to condense back into a liquid and eventually a solid.

Therefore, by understanding the movement of particles and the strength of intermolecular forces, we can explain the changes of state of matter.

 

The degree of randomness, or entropy, generally decreases from the gaseous state to the liquid state and to the solid state. This is because in a gaseous state, molecules have more kinetic energy and move around more freely, leading to a higher degree of disorder or randomness. In contrast, in a solid state, molecules are packed closely together and have little room to move, resulting in a more ordered arrangement.

However, it is important to note that this trend may not always hold true in every situation, and there can be exceptions. For example, when a substance undergoes a phase transition, such as melting or boiling, the degree of disorder may actually increase temporarily before settling into a new state with lower entropy. Additionally, some solids can exhibit a high degree of disorder, such as glasses or amorphous solids.

Overall, while the trend of decreasing randomness from gas to solid is generally true, it is important to consider the specific properties and behavior of each substance to fully understand its entropy and degree of orderliness.

 

here are some examples of changes of state using different substances:

1) Water

• Solid to liquid: When ice cubes melt into water, it is an example of a solid (ice) changing into a liquid (water) due to an increase in temperature.
• Liquid to gas: When water boils and turns into steam, it is an example of a liquid (water) changing into a gas (steam) due to an increase in temperature.
• Solid to gas: When dry ice (solid carbon dioxide) sublimates and turns into carbon dioxide gas, it is an example of a solid (dry ice) changing into a gas (carbon dioxide) due to a decrease in pressure.

 

2) Iodine

Solid to gas: When solid iodine is heated and turns into a purple gas, it is an example of a solid (iodine) changing into a gas (iodine vapor) due to an increase in temperature.

 

3) Sulphur

• Solid to liquid: When solid sulphur is heated and melts into a red liquid, it is an example of a solid (sulphur) changing into a liquid (molten sulphur) due to an increase in temperature.
• Liquid to gas: When liquid sulphur is heated and turns into a yellow gas, it is an example of a liquid (molten sulphur) changing into a gas (sulphur vapor) due to an increase in temperature.

 

4) Naphthalene

Solid to gas: When solid naphthalene (mothballs) are heated and turn into a gas, it is an example of a solid (naphthalene) changing into a gas (naphthalene vapor) due to an increase in temperature.

 

This motion can be observed using various experiments, including observing pollen grains or powdered sulfur in water under a microscope. Here’s how you can illustrate Brownian motion using these experiments:

1. Pollen grains in water: Take a drop of water and add a few pollen grains to it. Place the drop of water on a microscope slide and observe it under a microscope. You will see that the pollen grains move randomly in all directions. This movement is due to the collisions between the water molecules and the pollen grains, which causes them to move randomly.
2. Powdered sulfur in water: Take a small amount of powdered sulfur and add it to a glass of water. Stir the water gently and observe it under a microscope. You will see that the sulfur particles move randomly in all directions. This movement is due to the collisions between the water molecules and the sulfur particles, which causes them to move randomly.

In both cases, the movement of the particles is random and unpredictable. This is because the collisions between the fluid molecules and the particles are random and occur in all directions.

 

To observe Brownian motion using smoke in a glass container, you can follow these steps:

1. Fill a clear glass container, such as a beaker or a jar, with air and allow it to settle for a few minutes.
2. Light a strong source of light, such as a flashlight, and shine it through the side of the container so that the beam passes through the air.
3. Blow smoke into the container using a smoking stick or incense.
4. Observe the smoke particles as they move around in the air, which is visible due to the light shining through the container. The smoke particles will move randomly and erratically due to collisions with other air molecules, which is an example of Brownian motion.
5. You can also try tapping the container gently or blowing air onto it to see how the smoke particles respond to different types of movements.

Overall, the smoke in a glass container illuminated by a strong light from the side is a simple and effective way to observe Brownian motion and understand the concept of random particle movement in a fluid.

 

This phenomenon can be observed in many different contexts, including in a dusty room being swept and viewed from outside under sunlight.

To illustrate Brownian motion using this experiment, imagine a room that hasn’t been cleaned for a while and has accumulated a significant amount of dust. When the room is swept, the broom’s bristles will create air currents that will cause the dust particles to become suspended in the air.

If you observe this dusty room from outside under sunlight, you will notice that the dust particles appear to be moving randomly in all directions, even though there is no apparent source of motion. This movement is due to the Brownian motion of the particles, as they collide with air molecules and change direction randomly.

The dust particles’ random motion is similar to the motion of gas molecules in a container, which can also be observed using Brownian motion experiments.