# Is boiling point a physical property

In this article, we will discuss the properties of boiling point and whether boiling point is a physical property or not along with detailed facts.

Boiling point is the physical property of a substance because we can measure the temperature of a boiling liquid without affecting the chemical properties of the liquid.

## How is boiling point a physical property?

Boiling point is the temperature at which the system changes its phase from one form to another.

The heat energy supplied to the liquid from external sources is converted into thermal energy which increases the temperature of the liquid which is measured using a thermometer, hence it is a physical property of liquids.

As a result of boiling point the liquid state of the substance changes to the vapor state. This is evident due to the fact that the gap between the molecules increases, resulting in a physical change of matter.

The boiling point leads to a change in the phase of matter, and the amount of molecules occupying space also increases, and therefore the density of the substance decreases.

## Is a change in boiling point a physical property?

The boiling point also depends on the chemical composition, density of molecules and atmospheric pressure.

If you lower the pressure at which the liquid boils then the boiling point of the liquid will decrease; Whereas if the pressure exerted increases the liquid will start boiling at a higher temperature.

The boiling point is directly proportional to the pressure to which the system is exposed. So, according to the ideal gas law,

“The product of the volume of the molecules present in the system and the pressure incident on the system is equal to the temperature of the system and the universal gas constant.”

It is given by the relation, PV=nRT

where P is the pressure

V is the volume of the system

T is a temperature

R is a gas constant which is 8.314 J/mol K. Is equal to

n is a number of moles

At constant temperature, the volume is inversely proportional to the pressure on the system. As the pressure increases, the volume of the system decreases. And at constant pressure, the volume of the system exceeds the heat energy required to raise the temperature of a system.

The boiling point is related to temperature and pressure by the Clausius-Clapeyron equation:

ln\left ( \frac{P}{P_0} \right )=\frac{\Delta H_{vap}}{R}\left [ \frac{1}{T}-\frac{1}{T_B} \right ]

where is the temperature of the boiling point

T is the temperature of a liquid

R is an ideal gas constant R=8.314 J/mol K

P is vapor pressure

0 Temperature T . there is pressure on

is the heat of vaporization

The heat of vaporization is the amount of heat required to convert the phase of the liquid into vapor.

We can formulate the equation for boiling point from this equation, so we have

T_B=\left ( \frac{1}{T}-\frac{8.314\ ln\frac{P}{P_0}}{\Delta H_{vap}} \right )^{-1}

The change in boiling point is due to variation in pressure, which is a physical property. Also, there is no variation in the chemical properties of the liquid or any other changes observed in the substance. Therefore, the change in boiling point is clearly a physical property of the liquid.

## How is a change in boiling point a physical property?

The boiling point of a liquid can be measured and the variation in boiling point can also be determined.

Changes in boiling point are caused by changes in pressure or by adding impurities to the volume of a liquid. But the boiling point does not change in a liquid, although it increases the separation distance between the molecules.

The physical properties of matter can be measured or observed without changing any of the chemical properties of the substance. When the system is exposed to an external heat source, the heat energy is converted into thermal energy. The molecules that make up the liquid move back and forth from each other, reducing the system’s density per unit volume of the liquid. This energy is acquired by the molecules and released into the air, gaining sufficient potential energy.

## What is the change in the boiling point of water on adding a pinch of sodium chloride weighing 15 grams?

We know that the boiling point of water is 100 °C and the atmospheric pressure is 1atm.

The atomic mass of the cation of the salt Na is 22.99 g. is

The atomic mass of one ion of the salt Cl is 35.45 g. is

Therefore, the atomic mass of sodium chloride salt is 22.99+35.45 = 58.44 g

The moles of NaCl added to boiling water are

mol\ of\ NaCl= \frac{15g\times 1\ mol}{58.44g}

mol\ of\ NaCl= 0.2567\ mol

If the volume of water in a beaker is 100 ml, then the mass of the water is

m = \varrho v
M = 1\times 100=100\ grams= 0.1 kg

The molality of the solute in the solvent is

m=\frac{moles\ of\ solute}{mass\ of\ solvent}
m=\frac{0.2567}{0.1}=2.567\ mol/kg

Therefore, the variation observed in the boiling point of water is

\delta t = ik_bm

Here, in this case, the Vant Hoff factor i=2 because the two ions of sodium and chlorine will dissociate in water.

\delta t=2\times 0.51\times 2.567=2.62^0C

The variation in boiling point temperature of water we have calculated is 2.620C. Thus, by adding 15 grams of sodium chloride to 100 ml of water, the boiling point of water will be 100+2.62 = 102.62 0 C.

## Does the boiling point of a liquid change when salt is added?

The ice cream parlor uses salt to maintain the temperature up to freezing point to prevent the ice from freezing.

When a grain of salt is added to the liquid, the temperature of the liquid drops slightly because the surrounding heat energy is absorbed by the salt and more time is needed to reach the temperature at the boiling point.

## Does the boiling point of a liquid change due to the presence of impurities?

The presence of impurities changes the boiling point of the liquid.

The heat energy supplied to the liquid is taken up by the particles of impurities present in the liquid and hence the boiling point of the liquid may increase.

## What is the effect on boiling point as pressure increases?

Pressure is directly related to the temperature of the system.

As the pressure increases, the temperature required to boil the liquid will also increase, increasing the boiling point of the liquid.