(1) The characteristics of gases are described fully in terms of four parameters or measurable properties: (i) The volume, V, of the gas. (iv) The amount of the gas (i.e., mass or number of moles).

Observable properties include measurements like height, weight, temperature, and the volume of an object. Explanation: Observable properties are things we can use our five senses to determine, the measurable properties in the question need a tool like a thermometer or a ruler to determine.

Hint – The measurable properties of the gases are used for describing the physical state of a gas. The measurable properties of gases are mass, volume, pressure and temperature.

Besides pressure, denoted in equations as P, gases have other measurable properties: temperature (T), volume (V) and number of particles, which is expressed in a mole number (n or mol). In work involving gas temperature, the Kelvin scale is often used.

Heat of vaporization of water Water’s heat of vaporization is around 540 cal/g at 100 °C, water’s boiling point. Note that some molecules of water – ones that happen to have high kinetic energy – will escape from the surface of the water even at lower temperatures.

In order to evaporate water, the considered water sample has to be heated to its boiling temperature at the given pressure, and then further heat must be supplied, which corresponds to the enthalpy of vaporization. The enthalpy of the water can by increased by any kind of heat transfer.