Solid, liquid and gaseous - each substance can be under certain conditions in these states of aggregation. Evaporation and boiling are the process of transition of a substance from a liquid to a gaseous state.
Definition
Evaporation - the process of vaporization from the surface of the liquid.
Boiling is the process of vaporization in a liquid.
Comparison
Evaporation from the surface of any liquid always occurs at any temperature. The molecules of the liquid are located almost closely to each other, they oscillate about their equilibrium position and are interconnected by the forces of attraction. The molecules of the liquid are not attached to specific centers, so they can move throughout the liquid. But liquids always have a free surface, a boundary layer with a gas. Molecules in this layer are attracted from one side by molecules that are inside the liquid. But the fastest molecules, with a kinetic energy that is higher than the energy of their binding with the rest of the molecules, are able to fly out from the surface of the liquid. They, separated from the surface of the liquid, form a vapor above it. Some of the molecules can return back to the liquid due to chaotic movement, while the rest are irretrievably lost. For the remaining molecules, the average kinetic energy decreases, which leads to the cooling of the liquid.
Boiling is evaporation that occurs in the volume of the liquid itself. Water in its normal state at room temperature is saturated with air. There are always gas bubbles in a liquid even before boiling. When water is heated, the gas that it contains is released to the bottom and walls of the vessel. This is how air bubbles form. If the pressure of the saturated vapor of the liquid is equal to or exceeds the pressure of the gas in the bubbles, then the liquid will begin to evaporate in them. When heated, bubbles that are filled with steam inflate, expand and finally float to the surface. Boiling is a process in which there is a continuous formation and growth of vapor bubbles in a liquid, where the liquid evaporates. Boiling of a given liquid occurs at a certain temperature and at a certain pressure and is detected when vapor bubbles are formed in the entire liquid. This process will occur when the pressure of its saturated vapor is equal to the external pressure at a certain temperature.
Conclusions TheDifference.ru
- Evaporation is the transition of liquid into gas, which occurs from the boundary layer of the liquid.
- Evaporation of liquid takes place always at any temperature.
- Boiling is the process of vaporization in a liquid.
- Boiling occurs at a certain temperature and pressure.
