Evaporation and Condensation

Table of Contents

Evaporation and condensation are fundamental processes that play significant roles in the Earth’s water cycle and various natural phenomena. Evaporation is the process by which liquid water transforms into water vapour or gas, typically driven by heat energy from the sun. This transformation primarily occurs at the surface of water bodies, such as oceans, lakes, and rivers, as well as on wet surfaces like soil and vegetation. In contrast, condensation is the reverse process, where water vapour in the atmosphere changes back into liquid water.

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This occurs when the air cools down, causing the water vapour molecules to lose energy and form droplets. Evaporation and condensation are essential components of the water cycle, regulating water distribution on Earth and influencing weather patterns, cloud formation, and precipitation. Understanding these processes is crucial for comprehending the Earth’s atmosphere and eco dynamics.

What is Evaporation?

Evaporation is when a liquid, such as water, changes into a gas or vapour state. This transformation occurs when the liquid’s molecules gain enough energy from the surrounding environment, typically from heat, to break free from the liquid’s surface and enter the air as individual gas molecules. Evaporation commonly occurs from bodies of water, such as oceans, lakes, and rivers, as well as from moist surfaces like wet soil, puddles, or wet clothes. It is a vital part of the water cycle, where water evaporates from the Earth’s surface, rises into the atmosphere, and eventually condenses to form clouds and precipitation. It completes the cycle by returning water to the Earth’s surface.

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What is Condensation

Condensation is when a gas or vapour changes into a liquid state. This transformation occurs when the gas molecules lose energy and come together to form liquid droplets. It often happens when warm air cools down, causing the water vapour in the air to condense into tiny droplets of liquid water. You can see condensation on surfaces like windows when warm, moist air inside a room comes into contact with the cooler glass, causing the water vapour to turn into liquid droplets. Condensation is an essential part of the water cycle, where water vapour in the atmosphere condenses to form clouds, fog, and dew, ultimately leading to precipitation such as rain or snow.

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Difference between Condensation and Evaporation

Condensation and evaporation are two fundamental processes involving the transformation of water, but they occur under different conditions and result in opposite outcomes. Understanding the differences between condensation and evaporation helps us grasp how water moves and changes state in the natural environment. Now, let’s explore these differences further:

Aspect	Evaporation	Condensation
Definition	Evaporation is a process where water changes into a vapour.	Condensation is the opposite process, where water vapour is converted to tiny water droplets.
Occurrence	Evaporation occurs before a liquid reaches its boiling point.	Condensation is a phase change regardless of the temperature.
Molecular Movement	The forces of attraction between molecules are low when a liquid is heated or when pressure is decreased. The liquid then evaporates into a gas.	When a gas is cooled or the pressure increases, the forces of attraction between molecules become strong. The gas then condenses to either a liquid or even a solid.
Surfaces	Evaporation can occur on all surfaces, at all times and in all places. Evaporation is frequent when the air is dry, hot and windy.	Condensation occurs on salt, hygroscopic nuclei-pollen grains, carbon particles, etc., when the air temperature is decreased beyond saturation.
Energy Consumption/Release	When evaporation takes place, energy is consumed.	In the process of condensation, energy is released.

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What are the Various Processes that Bring about a Physical Change?

Various processes can bring about a physical change in matter. These processes include:

Melting: Melting is when a solid substance changes into a liquid state when heated to its melting point. For example, ice melts into water when heated.

Freezing: Freezing is the opposite of melting, where a liquid substance changes into a solid state when cooled to its freezing point. For instance, water freezes into ice when cooled.

Evaporation: Evaporation is when a liquid substance changes into a gaseous state due to the absorption of heat energy. This occurs at the surface of the liquid, such as when water evaporates to form water vapour.

Condensation: Condensation is the reverse of evaporation, where a gaseous substance changes into a liquid state when cooled. It happens when water vapour in the air cools down to form liquid water droplets, such as when dew forms on grass in the morning.

Sublimation: Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. An example is the sublimation of dry ice (solid carbon dioxide) into carbon dioxide gas.

Deposition: Deposition is the reverse of sublimation, where a gas changes directly into a solid without passing through the liquid phase. One common example is frost formation on surfaces when water vapour in the air directly turns into ice crystals without first becoming liquid water.

These processes are essential in understanding the behaviour of matter and how it can change from one state to another under different conditions of temperature and pressure.

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Experiment Of Evaporation and Condensation

Experiment: Investigating Evaporation and Condensation

Aim:

To observe and understand the processes of evaporation and condensation using simple household materials.

Materials:

A shallow dish or bowl
Water
Clear plastic wrap or cling film
Ice cubes or a cold pack
Heat source (e.g., sunlight or a lamp)

Procedure:

Preparing the Setup:

Fill the shallow dish or bowl with water until it is about halfway full.
Cover the top of the dish securely with clear plastic wrap or cling film, ensuring it is airtight.

Observing Evaporation:

Place the dish in a sunny location or near a lamp to expose it to heat.
Observe the dish periodically over the next few hours and record any changes you notice.

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Observing Condensation:

Once evaporation has occurred and the water level has decreased, place a few ice cubes or a cold pack on top of the plastic wrap.
Allow the dish to sit for some time, then observe the surface of the plastic wrap for any droplets or moisture that form.

Results and Discussion:

During the experiment, you should observe water droplets forming on the underside of the plastic wrap after the ice cubes are introduced. This is condensation, where water vapour in the air inside the container cools down and turns back into liquid water when it comes into contact with the cooler plastic wrap surface.

Prior to introducing the ice cubes, you would have observed the water level in the dish gradually decreasing over time. This is evaporation, where liquid water transforms into water vapour due to exposure to heat energy from the surroundings.

Conclusion:

Through this experiment, you have observed and understood the processes of evaporation and condensation in action. These phenomena are essential components of the water cycle and play significant roles in weather patterns and various natural processes.