In my point of view coal contains large amount of carbon so that's why it don't catches flame

Introduction:
When coal burns, no flame is observed, whereas a flame is observed when a candle is lighted. This difference can be attributed to the nature and composition of coal and candles.

Composition of Coal:
Coal is primarily composed of carbon, along with small amounts of other elements such as hydrogen, sulfur, and nitrogen. It is a solid fuel that undergoes a process called combustion when it is burned. During combustion, the carbon in coal combines with oxygen from the air to produce carbon dioxide, water vapor, and heat energy.

Combustion Process:
The combustion process involves three essential components: fuel, oxygen, and heat. When coal is heated, it undergoes a process known as pyrolysis, where the complex organic compounds in coal break down into simpler molecules. The released volatile gases then mix with oxygen in the air and burn, releasing heat energy. However, since coal is a solid fuel, it does not vaporize completely and does not produce a visible flame.

Flame in Candles:
Candles, on the other hand, are made of solid wax, typically composed of hydrocarbons. The most common wax used in candles is paraffin wax, which is derived from petroleum. When a candle is lit, the heat from the flame melts the wax near the wick, and the liquid wax is drawn up the wick. The heat of the flame vaporizes the liquid wax, and the vapor combines with oxygen from the air to undergo combustion.

Visible Flame:
The visible flame observed in candles is a result of the combustion process. The heat of the flame provides the energy needed to break the hydrocarbon molecules in the wax, releasing carbon dioxide and water vapor. The heat also excites the carbon particles in the flame, causing them to emit visible light. The emission of light is what we perceive as a flame.

Difference:
The main difference between coal and candles in terms of flame production lies in their physical state and composition. Coal is a solid fuel that undergoes incomplete combustion, resulting in the release of heat energy without a visible flame. Candles, on the other hand, are made of hydrocarbons that can vaporize and undergo complete combustion, producing a visible flame.

Conclusion:
In summary, the absence of a visible flame when coal burns can be attributed to its solid nature and incomplete combustion. Candles, being made of hydrocarbons that vaporize and undergo complete combustion, produce a visible flame. The composition and physical properties of these fuels play a crucial role in the presence or absence of a flame during the combustion process.