Phase Change

Slides - Phase Change
Related Activities - Force / Pressure / Energy

(1) Collapsing Can

Sourcebook for Teaching Science 5.1.2, Hands-On Chemistry 2.4.1, Hands-On Physics 4.1.1

(2) Air Pressure Fountain

Hands-On Physics 4.1.1-teacher section page 206; Air Pressure Fountain

(3) Candle in Flask

Source: Hands-On Physics 4.1.4
1. Video: Extinguishing a Candle in Flask;
2. Diagram: Candle in Flask
3. Simulation: Phases of matter (PHET)
4. Simulation: Gas Laws (Edumedia)

(4) Boiling by Cooling

(5) Phase Changes

Melting: This is the phenomenon in which a solid substance transitions into a liquid phase due to an increase in temperature. This process is endothermic, meaning it requires energy to occur.
Freezing: This is the opposite of melting and occurs when a liquid substance transitions into a solid phase due to a decrease in temperature. This process is exothermic, meaning it releases energy as heat.
Vaporization: This is the process by which a liquid substance transitions into a gas phase. There are two types of vaporization: evaporation, which occurs at the surface of the liquid, and boiling, which occurs throughout the liquid.
Condensation: This is the opposite of vaporization and occurs when a gas transitions into a liquid phase. This process is exothermic and releases energy as heat.
Sublimation: This is the process by which a solid transitions directly into a gas phase without first passing through the liquid phase. This process is endothermic and requires energy to occur.
Deposition: This is the opposite of sublimation and occurs when a gas transitions directly into a solid phase without passing through the liquid phase. This process is exothermic and releases energy as heat.

(6) Applications

Boiling water: When water is heated, it reaches its boiling point and undergoes a phase change from a liquid to a gas, producing steam. This phenomenon is important in many industrial and domestic applications, including cooking, sterilization, and power generation.
Formation of clouds: Clouds are formed when warm, moist air rises and cools, causing the water vapor in the air to undergo a phase change and condense into tiny droplets or ice crystals. This process of condensation is also responsible for the formation of fog, dew, and precipitation.
Solidification of metals: Many metals can be cast into different shapes by melting them and pouring them into molds. When the molten metal cools, it undergoes a phase change from a liquid to a solid, forming the desired shape.
Refrigeration: The refrigeration process relies on the phase change of a refrigerant from a liquid to a gas and back again. As the refrigerant evaporates, it absorbs heat, causing the surrounding air or liquid to cool. When the refrigerant condenses back into a liquid, it releases heat, which is carried away by a cooling system.
Climate change: Changes in the Earth's climate are closely related to the phase changes of water in the atmosphere, particularly the amount of water vapor and the formation of clouds. Understanding these phenomena is essential for predicting and mitigating the effects of climate change.
Heat transfer: Phase change plays a critical role in the transfer of heat energy. For example, during the process of boiling, heat energy is absorbed by the liquid as it changes phase into a gas. Similarly, during the process of condensation, heat energy is released by the gas as it changes phase into a liquid. These phase changes help regulate temperature in many industrial and environmental systems.
Crystallization: When a liquid substance undergoes a phase change to a solid, it can form crystalline structures with unique properties. For example, the formation of ice crystals during the freezing of water can lead to the formation of snowflakes, which have intricate and beautiful patterns.
Thermal energy storage: Phase change materials, such as certain types of waxes, can be used to store thermal energy. These materials can absorb large amounts of energy when they change phase from solid to liquid or liquid to gas, and then release that energy when they change back to a solid.
Superconductivity: Certain materials can undergo a phase change at very low temperatures, becoming superconducting and allowing for the flow of electrical current without resistance. This phenomenon has important applications in fields such as medical imaging, transportation, and energy storage.
Geological processes: The movement of the Earth's crust and the formation of rocks and minerals can be explained by phase change phenomena. For example, the formation of igneous rocks involves the cooling and solidification of magma, while the formation of metamorphic rocks involves the alteration of existing rocks due to high pressure and temperature.