<p>Rates and intensities of evaporation of liquid n-heptane, aviation kerosene, ethanol, and water have been determined experimentally in an air atmosphere under normal conditions and at a temperature elevated within 25–70°C under the conditions of natural convection from the open surface of the liquids of area 4.9–141 cm². Velocities of propagation of the flame along the channels of varying width over the surface of liquid ethanol have been measured. A relationship has been established between the velocity of propagation of the flame and the intensity of evaporation. Experimental results demonstrate the nonlinear dependence of the evaporation rate on temperature and the linear dependence of the rate of evaporation on its area at a value of the open-surface area larger than 78.5 cm².</p>