The major difference between evaporation and boiling is that evaporation is gradual process that occur at the surface of the liquid at any temperature while, boiling is rapid process that can occur through the entire liquid at specific temperature.
What Is Evaporation?
Evaporation happens when a liquid at the surface transforms into a gas or vapor. This process occurs daily on Earth as part of the water cycle. For the water cycle to function, water needs to move from the Earth’s surface into the atmosphere. Most of the water that becomes vapor in the water cycle originates from the Earth’s oceans. This invisible process is known as evaporation.
Process of evaporation:
Evaporation occurs when a liquid is heated, causing its molecules to gain kinetic energy. As these molecules absorb energy, they start to move apart and vibrate more rapidly, leading the liquid to transform from a liquid state to a gas.
Water is a common example of a substance that undergoes evaporation. When heat is added to water, the bonds between its molecules begin to break, causing the water to change from a liquid into a gas. This transformation occurs at the water’s boiling point, which is 212 degrees Fahrenheit or 100 degrees Celsius.
Evaporation plays a practical role in everyday life. For example, when someone swims, their bathing suit dries over time because the Sun’s heat causes the water molecules in the suit to evaporate into the air. Similarly, the process of salt crystal formation involves seawater being exposed to the Sun. The Sun evaporates the water, leaving behind salt crystals.
What is Boiling?
The boiling point is the temperature at which the pressure exerted by the surrounding environment on a liquid equals the pressure exerted by the liquid’s vapor. At this temperature, additional heat causes the liquid to transform into vapor without further increasing the temperature.
At any given temperature, a liquid partially evaporates into the space above it until the vapor pressure reaches a specific value known as the vapor pressure of the liquid at that temperature. As the temperature rises, the vapor pressure increases. At the boiling point, vapor bubbles form within the liquid and rise to the surface.
The boiling point of a liquid depends on the applied pressure; the normal boiling point is the temperature at which the vapor pressure equals the standard atmospheric pressure at sea level (760 mm or 29.92 inches of mercury). For example, at sea level, water boils at 100°C (212°F). However, at higher altitudes, the boiling point is lower.
Evaporation vs Boiling
The primary difference between evaporation and boiling is given below:
| Aspect | Evaporation | Boiling |
| Definition | The process where a liquid changes into a gas at its surface. | The process where a liquid changes into a gas throughout its entire volume. |
| Temperature | Can occur at any temperature. | Occurs at a specific temperature known as the boiling point. |
| Location | Takes place only at the surface of the liquid. | Takes place throughout the entire liquid. |
| Pressure Influence | Occurs at any atmospheric pressure. | The boiling point changes with atmospheric pressure; higher pressure raises the boiling point. |
| Energy Required | Relatively low energy is needed. | Requires a significant amount of energy. |
| Speed | Generally slow. | Generally fast. |
| Examples | Water drying on a surface, sweat evaporating. | Water boiling in a pot, steam from a kettle. |
| Vapor Formation | Vapor forms gradually at the surface. | Bubbles of vapor form inside the liquid and rise to the surface. |
| Phase Transition | Liquid to gas at the surface only. | Liquid to gas throughout the liquid volume. |
| Resulting Temperature | Temperature of the liquid remains relatively constant during evaporation. | The temperature of the liquid remains constant at the boiling point during boiling. |