When thermal energy is supplied to melt a solid, the temperature remained constant during the melting point. Explain what happened to the heat energy supplied.
During melting, thermal energy absorbed is used to break the intermolecular bonds between the particles, resulting in increase in potential energy of the substance.
Thermal energy is not used to cause an increase in kinetic energy of the particles, hence temperature remains constant.
*Using the kinetic model of gases, explain why evaporation of a liquid causes a fall in temperature.
In a sample of water, the molecules move at different speeds, and therefore different kinetic energies.
At the water surface, molecules with sufficient energy to overcome the attractive forces of other molecules escape into the atmosphere.
When energetic molecules escapes from the surface of a liquid, its leaves behind the less energetic molecules.
As a result, the average kinetic energy of the remaining molecules decreases and therefore the temperature of liquid falls.
Which will cause a more severe injury? Scalding by boiling water at 100 degree Celsius or steam at 100 degree Celsius?
Scalding by steam at 100 degree Celsius.
Although both are of the same temperature, the latent heat of vaporization of steam is greater than specific heat capacity of water.
A larger amount of latent heat of vaporization is released as steam condenses on the skin, as compare to thermal energy released as water contacts the skin.