Why is the colour of fire yellow, red and blue?

The fire has great importance in our daily life. Its reason is that we are using fire for various purposes like we are using it for generating heat, we are using it for generating light and we are also using it for cooking food etc. There are various ways to generate fire like stove, oven and Bunsen burner etc. While generating fire, we also notice that these flames have different shapes and colours but most of the fire flames have a yellow, red or blue colour. When we see the yellow, red or blue colour of the fire flame, a question comes to our mind that ‘Why is the colour of fire yellow, red or blue?’.
Why is the color of fire yellow, red and blue?

Elements of Fire

Before getting an idea about different colours of fire, we should try to know about the elements of fire. To understand the elements of fire, we should try to know about the fire triangle. In the fire triangle, there are three ingredients. These three ingredients are explained below;

1.     Heat

For the initial ignition of the fire, first of all, we require a heat source. This heat source is also required to maintain the fire and to spread it in the surrounding area. With the help of heat, it is also possible for the fire to warm the surrounding area.

2.     Fuel

Any kind of the combustible material which is required to produce fire is known as fuel. It is easy for us to characterize the fuel into different categories on the basis of size, shape and quantity etc. The moisture content of this fuel also tells us how easy or difficult will be fire produced.

3.     Oxygen

The burning of fire is a chemical process and Oxygen is known as the main ingredient of this chemical process. The percentage of Oxygen in the air is almost 21% and most of the fires require just 16% of Oxygen for the burning process. Therefore, we can also say that the burning of fire is also an oxidation process. In order to burn fuel, there requires Oxygen from the surrounding area.

Related article: Why do human eye see different colors? 

Why is the colour of fire yellow?

The chemical makeup of the flame is the main factor that determines the colour of the fire. In the chemical makeup of the flame, there come two things. First of all, what you are burning and secondly, what is the temperature of the flame. The chemical combination of the wood, paper and hydrocarbon fuels is such that it gives either yellow colour to the fire or reddish-orange colour to the fire. Moreover, yellow or reddish-orange colour of the fire is also due to the presence of the carbon particles in the flame.

How does colour of fire change?

It is also a fact that if we are burning different fuels, the colours of their fire are also different. It is due to the difference in the flame temperature. Moreover, it is also possible for us to change colours of fire by changing the accessibility of the fire. If we restrict the accessibility of Oxygen, the colour of fire will be dim red. In a similar way, if we are burning fuel in the higher accessibility of Oxygen, it will burn all the Carbon atoms before creating colour. Under such a situation, the colour of the flame will be blue.

Different colours of fires and their temperatures

As we have discussed earlier that the temperature of different colours of fire is different. Here, we will discuss three main colours of fire and their temperature ranges. If the temperature of the fire is in between 600-1000°C, its colour will be red. On the other hand, if the temperature of the fire is in between 1000-1200°C, its colour will be yellow. In a similar way, if the temperature of the fire is in between 1200-1400°C, its colour will be blue. Therefore, we can say that the blue flame is known as the hottest flame.
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