Types of Phase Changes and Key Properties
Each material can transform into three phases: solid, liquid, or gas. Every substance is in one of these three phases at a certain temperature. The intermolecular forces acting on the material's molecules and atoms significantly impact the temperature and pressure at which the substance will change. Two phases may dwell in the same container at the same time. This usually occurs during the change from one phase to another. It's known as a two-phase condition. When the ice melts, the container contains liquid and solid water both.
Deposition
Thermal energy must be removed for a material to transition from its physical state from gas to solid; this process is called deposition. Particles in a gas have a greater quantity of kinetic or moving energy, and they vibrate at a high rate. Particles in a solid have less kinetic energy and vibrate more slowly without changing position. The reason it is termed deposition is that gaseous particles are deposited into the solid form. Gas to solid is called deposition.
Gas to Solid Examples
To create dry ice, gaseous carbon dioxide must first be drawn out of the atmosphere. Using colder temperatures and higher pressure, the gas particles skip the liquid phase and settle into a solid to create dry ice. This is one of the deposition examples.
Gas to solid process can be in a carbon dioxide fire extinguisher is initially filled with gaseous carbon dioxide, but the increased pressure inside the canister causes this to solidify and get expelled as a white powder when extinguishing a fire.
Condensation and Vaporisation
Condensation
When the gas is converted into liquid form by freezing or by any other method, then it is known as the condensation process.
Gas to Liquid Examples
As the water vapour cools in the sky, clouds are created. Tiny water droplets form when the temperature of the water vapour reaches the dew point or lower. These droplets condense onto microscopic airborne dust particles to form clouds.
Vaporisation
Vaporisation is the process by which a material is transformed from its liquid or solid state into its gaseous (vapour) state. Boiling is the term for the evaporation process. Evaporation merely refers to a form of vaporisation that mostly occurs below the boiling point of water.
Liquid to Gas Examples
The steam that rises from a hot cup of coffee is a typical illustration of evaporation. The heat escaping from the cup aids in the cooling of the coffee.
Freezing and Melting
Freezing
The process through which a material transforms from a liquid to a solid is known as freezing. When a liquid's molecules slow down enough to attract one another into permanent positions as a solid, this process is known as freezing.
Liquid to Solid Examples
Freezing is used in food preservation techniques that involve decreasing the temperature to stop bacterial development.
Melting
Melting occurs when heat is applied, and a solid transforms into a liquid. An impure solid often melts across a range of temperatures below the melting point of the primary component, whereas this process happens in pure crystalline solids at a set temperature known as the melting point.
Solid to Liquid Examples
Melting of steel is done to make different types of products of steel. In this process, first, the steel is converted into the molten state by heating at a high temperature and then poured into a mould for any desirable shape.
Sublimation
Sublimation is the process of changing the material from its solid to gaseous form without it being liquid, according to Physics.
Solid to Gas Examples
Dry ice can be created by blending and freezing carbon dioxide (CO2). At ambient temperature, this returns to its initial gaseous state.
Describe All Different Types of Phase Changes
Given below is the list of all the different types of phase changes in physics and chemistry.
Sublimation
Sublimation is the process where the matter changes its state from solid to gas without being converted into liquid in the first place. One of the examples of sublimation is the naphthalene balls that you use to keep your winters clothes packed and safe in summer.
Deposition
The opposite of sublimation is deposition, here the matter is present in the gaseous state, and as the reaction occurs, it changes into soil state without being converted into a liquid which is the intermediate state. An example of this is hard to find because you need to have a sub-zero temperature to achieve it. But in higher altitude and south and north pole, we can see vapours of water being converted into solid ice without getting into their liquid state.
Melting
When a matter changes its state from solid to liquid, for example, ice cubes, when taken out from the freezer, start to melt.
Boling
Boling of a matter occurs when it reaches a certain temperature, its a non-natural process and requires a high amount of heat. Boling water to kill bacteria inside it is also a non-natural process.
Freezing
When a matter changes from liquid to solid, when you put water in the freezer, and it converts into ice.
Condensation
When a matter changes itself from the gaseous state to liquid state, water particles in the air get condensed when they come in contact with a cold water bottle.
Evaporation
Changing of liquid matter into a gaseous state. The water in the ocean evaporates to form clouds in the atmosphere.
Interesting Facts
Treatment of iodine. Iodine crystals are heated in a laboratory to produce a purple gas that has a distinctive smell.
The melting of ghee in a frying pan.
Snowfall and snowflakes are also examples of freezing.
Summary
Phase transitions (also known as phase changes) are the physical processes of changing from one state of a medium identified by a set of parameters to another with a set of parameters that have a different value. The phrase is frequently used to describe changes in the three fundamental states of matter: solid, liquid, and gas and, in rare instances, plasma.
FAQs on Phase Changes in Chemistry
1. What is a phase change in chemistry?
A phase change is a physical process where a substance transitions from one state of matter (solid, liquid, or gas) to another. This change typically occurs when heat energy is either added to or removed from the substance at a specific temperature and pressure, causing a rearrangement of its molecules without altering its chemical identity.
2. What are the six main types of phase changes?
The six primary phase changes describe the transitions between the three common states of matter:
Melting: The transition from a solid to a liquid.
Freezing: The transition from a liquid to a solid.
Vaporization (Boiling/Evaporation): The transition from a liquid to a gas.
Condensation: The transition from a gas to a liquid.
Sublimation: The transition directly from a solid to a gas, skipping the liquid phase.
Deposition: The transition directly from a gas to a solid, skipping the liquid phase.
3. What is the key difference between evaporation and boiling?
The key difference lies in where and at what temperature they occur. Evaporation is a surface phenomenon that can happen at any temperature below the boiling point; only particles at the liquid's surface gain enough energy to escape. In contrast, boiling is a bulk phenomenon that occurs at a specific temperature (the boiling point) where bubbles of vapour form throughout the entire volume of the liquid.
4. Can you provide a real-world example of deposition?
A common example of deposition is the formation of frost on a cold morning. Water vapour (a gas) in the air comes into contact with a surface whose temperature is below freezing point (0°C). The water vapour instantly changes into ice crystals (a solid) without first becoming liquid water. This direct gas-to-solid transition is deposition.
5. What happens to the molecules of a substance during melting?
During melting, the molecules in a solid absorb heat energy. This energy increases their kinetic energy, causing them to vibrate more vigorously. Eventually, they gain enough energy to overcome the strong intermolecular forces holding them in a fixed, orderly lattice structure. The molecules can then slide past one another, and the substance transitions into the more disordered liquid state.
6. Why does the temperature of water remain constant at 100°C while it is boiling?
While water is boiling, the temperature stays constant at 100°C because the added heat energy is not used to increase the kinetic energy of the molecules (which would raise the temperature). Instead, the energy is entirely used to overcome the intermolecular forces holding the water molecules together in the liquid state. This energy is known as the latent heat of vaporization, and it facilitates the phase change from liquid to gas (steam).
7. Are clouds a gas?
This is a common misconception. Clouds are not a gas. While they exist within the air (a mixture of gases) and contain invisible water vapour (a gas), the visible part of a cloud is actually a massive collection of tiny liquid water droplets or ice crystals. These particles are so small and light that they remain suspended in the atmosphere.
8. How do pressure cookers cook food faster by manipulating phase change?
A pressure cooker works by increasing the pressure inside the sealed pot. The boiling point of a liquid is the temperature at which its vapour pressure equals the external pressure. By increasing the pressure above normal atmospheric pressure, the pressure cooker forces the water to boil at a higher temperature (e.g., around 121°C instead of 100°C). This elevated boiling point allows the food to be cooked in liquid water that is significantly hotter, drastically reducing cooking time.
9. What is a phase diagram and what does the 'triple point' signify?
A phase diagram is a graphical representation that shows the preferred physical state of a substance under different conditions of temperature and pressure. The diagram has regions for solid, liquid, and gas phases. The triple point is a unique and specific point on this diagram where the temperature and pressure conditions are just right for all three phases—solid, liquid, and gas—to coexist in thermodynamic equilibrium.
10. Under what conditions can a gas like oxygen be turned into a liquid?
To turn a gas like oxygen into a liquid, it must be cooled below its critical temperature (-118.6°C) and subjected to high pressure. Above this critical temperature, no amount of pressure can liquefy the gas. By significantly lowering the temperature, the kinetic energy of the oxygen molecules is reduced, allowing the intermolecular forces to take effect and pull the molecules together into a liquid state when pressure is applied.
