Vaporization and Boiling Point – Explanation with Example

Vaporization and Boiling Point

Introduction

The temperature at which liquid converts to gas is called the boiling point. Boiling occurs when the vapor pressure of liquid and atmospheric pressure becomes equal. At this point liquid becomes gas. 

When we apply heat to the liquids, the particles slowly gain energy and move freely around all parts of the substance. Bubbles of vapor form within the liquid. These bubbles are the gaseous form of the substance. 

Explanation

What is meant by boiling point and vaporization? 

A liquid boil at a temperature at which its vapor pressure is equal to the atmospheric pressure of the gas above it. The lower the pressure of a gas above a liquid, the lower the temperature at which the liquid will boil. 

Changing of liquid to vapor can be observed in the form of bubbles. Bubbles of liquid form within the substance will burst and release the gas on applying the heat. This explains that before bursting the bubble of liquid forms into the gas, the bubble has enough pressure to keep it without collapsing. 

Before collapsing the bubble into the gas, the liquids must undergo some force of attraction between the particles.  

The boiling point of any substance is the temperature at which liquid substances start heating and changing to the gaseous state. This means that the boiling point of the liquid is 100^oC. The temperature always remains constant when you even apply more heat than the required amount. 

In the hill stations or mountain areas, atmospheric pressure is lower than the sea level. So that’s the reason the food cooks only at a lower temperature.  

Atmospheric Pressure 

The Celsius scale is based on melting point and boiling point. The boiling point of any substance will always be dependent on the atmospheric pressure. 

Factors that affect the boiling point: 

The boiling point of a liquid is the temperature at which its vapor pressure is equal to the atmospheric pressure of the gas above it. The normal boiling point is the temperature at which vapor pressure is equal to one atmosphere. 

If the external pressure < 1atm, the boiling point is less than the normal boiling point. 

If the external pressure = 1atm, the boiling point of the liquid is called the normal boiling point. 

If the external pressure is> 1atm, the boiling point of the liquid is greater than the normal boiling point. 

Vaporization: 

Vaporization is the process by which a liquid change to a gas.  Evaporation happens at the surface of a liquid at any temperature below the liquid’s boiling point. During evaporation, some molecules at the surface have enough energy to escape. 

Examples: 

1. The boiling point of fresh water at sea level is 212°F (100°C) 

2. Pressure cooker. 

3. Boiling of milk. 

4. Cup of coffee at mountain or hill station