The Science behind the Candle Flame with Diagram and Its Working Explained

Have you ever looked closely at a burning candle and wondered why its flame has different colours? A candle flame may seem simple, but it is actually a fascinating example of combustion and energy transformation. When a candle burns, the wax reacts with oxygen in the air and produces heat and light. The flame is divided into different zones, each having its own colour, temperature and function. This article focuses on the candle flame diagram , its structure, different zones, types of flames and why each part of the flame behaves differently. 

Table of Contents 

• What is Candle Flame
• Structure of Candle Flame
• Types of Candle Flame
• Different Zones of Candle Flame

What is Candle Flame 

A candle flame is the visible, glowing region where the vapour of molten wax burns in the presence oxygen. It is produced due to a chemical reaction called combustion, in which wax reacts with oxygen to form carbon dioxide, water vapour, heat and light.

In Simple Words,

A candle flame is the hot, glowing part of a burning candle where wax vapour combines with oxygen and releases energy.

Must-Know Facts About Candle Flame!

Nearly one-fourth of the energy produced by a candle is released as heat. The flame actually burns wax vapour, not solid wax. A candle can continue burning only if oxygen is available. The blue outer region is the hottest part of the flame. Different coloured flames indicate different temperatures.

Have you ever thought how does candle burns:

The burning of a candle takes place in a series of steps:

1. Heat from a match melts the wax.
2. The melted wax rises through the wick.
3. The wax changes into vapour due to heat.
4. The vapour reacts with oxygen in the air.
5. Heat and light are produced, forming the flame.

This process continues until either the wax is used up or the oxygen supply is cut off.

Read More: Combustion Fuel and Heat of Combustion

Structure of Candle Flames

A candle flame is not uniform. It consists of different regions that vary in colour and temperature.

The colour of a flame mainly depends on:

• Nature of the substance going combustion
• Amount of oxygen available
• Temperature of combustion

Each region of the flame performs a different role during combustion and therefore has a different appearance.

Types of Candle Flame

There are mainly two types of flames.

1. Luminous Flame

A luminous flame is bright yellow and produces light.

Characteristics

• Formed due to incomplete combustion.
• Oxygen supply is limited.
• Produces soot particles.
• Gives more light but less heat.

Example: Candle flame's yellow region.

2. Non-Luminous Flame

A non-luminous flame is blue in colour and produces more heat.

Characteristics

• Formed due to complete combustion.
• Sufficient oxygen is available.
• Produces very little soot.
• Hotter than a luminous flame.

Example: The outer blue region of a candle flame.

Different Zones of Candle Flame

A candle flame consists of three distinct zones.

1. Outer Zone

The outermost region appears blue.

Characteristics

• Complete combustion takes place.
• Receives maximum oxygen.
• Hottest part of the flame.
• Non-luminous in nature.

Approximate Temperature: Around 1400°C.

2. Middle Zone

The middle region is bright yellow and produces most of the visible light.

Characteristics

• Partial combustion takes place.
• Moderately hot.
• Contains glowing carbon particles.
• Luminous region of the flame.

Approximate Temperature: Around 1000°C.

3. Inner Zone

The innermost region is dark or black.

Characteristics

• Contains unburnt wax vapours.
• Receives the least amount of oxygen.
• Coolest part of the flame.
• Combustion has not yet started completely.

Approximate Temperature: Around 600°C.

You may have noticed that why does a candle flame have different colours?

The different colours of the flame are due to differences in temperature and oxygen supply.

• Blue colour indicates complete combustion and high temperature.
• Yellow colour is produced by glowing carbon particles.
• Dark region contains unburnt wax vapours.

Thus, the colour of a flame gives important information about the combustion process taking place.

Another important observation is why is the outer zone the hottest?

The outer zone receives the maximum amount of oxygen from the surrounding air. Therefore, the wax vapour burns completely in this region and releases the greatest amount of heat energy.This is why laboratory experiments often use the outer blue zone of a flame for heating substances.

We have learned that candle flame diagram is much more than a source of light. It is a perfect example of combustion, energy conversion and chemical reactions. The flame is formed when wax vapour burns in oxygen and consists of three different zones, the outer blue zone, the middle yellow zone and the inner dark zone. Each zone has a different temperature and combustion process.