Question

Why does water evaporate?

Short answer

Water evaporates because its molecules, which are held together by hydrogen bonds, gain enough kinetic energy from the environment to break these bonds and escape as water vapor. This process, known as evaporation, is influenced by factors such as temperature, surface area, humidity, and air movement.

Step-by-step solution

Understand water molecules

Water is composed of molecules, each made up of two hydrogen atoms and one oxygen atom (H2O). These molecules are in constant motion, and they are held together by hydrogen bonds, which are relatively weak forces compared to other types of chemical bonds.

Learn about evaporation

Evaporation is a phase transition in which a substance changes from a liquid state to a gaseous state. In the case of water, this phase transition is called the vaporization of water, or simply, evaporation. Evaporation occurs when molecules of water gain enough energy to break the hydrogen bonds holding them together and escape into the surrounding air as water vapor.

Investigate the role of energy in evaporation

Molecules in a liquid possess different amounts of kinetic energy, which is the energy of motion. Some molecules have high kinetic energy, while others have low kinetic energy. As the liquid absorbs energy from the environment, the kinetic energy of the molecules increases. When a water molecule gains enough energy, its hydrogen bonds break, allowing it to escape as water vapor.

Discuss the factors influencing evaporation

There are several factors that can affect the rate of evaporation: 1. Temperature: As temperature increases, the kinetic energy of water molecules increases, causing more molecules to evaporate. 2. Surface area: The larger the surface area of the liquid, the more molecules are exposed to the environment, leading to a higher evaporation rate. 3. Humidity: If the air surrounding the liquid is already saturated with water vapor, the rate of evaporation will decrease, as the air cannot hold any more water vapor. 4. Air movement: When the air above the liquid is in motion, it helps to carry away water vapor, which increases the rate of evaporation.

Conclusion

Water evaporates due to the molecular motion, energy absorption, and the breaking of hydrogen bonds within the water molecules. When water molecules gain enough kinetic energy to overcome these bonds, they escape as water vapor. This process is influenced by factors such as temperature, surface area, humidity, and air movement.