What causes the colour of a flame?

Question

Naomi Aronson · Accepted Answer

The colour of a flame depends on three factors.

A flame is produced when something burns, that is, when it combines with oxygen in the air.

The process is called combustion.

The colour of the flame depend on

What is burning.
The temperature of the flame.
The amount of air (oxygen) that is supplied.
What is burning

A match burns with a yellow flame, but a piece of magnesium metal burns with a brilliant white light.

The temperature of the flame

As the temperature increases, the colours go from dark red to bright red, then to orange, then to yellow, and finally to white-blue.

Thus, different parts of the flame will have different colors depending on the temperature.

The hotter parts, closer to the burning fuels, will be whitish-blue. The parts that are further away will be cooler and orange-reddish.

Orange corresponds to a temperature of about 1000 °C.

The amount of air

If enough oxygen is available, the substance will burn completely (complete combustion).

If there is not enough oxygen, to burn everything (incomplete combustion), the flame temperature will be lower.

Also, unburnt material such as soot (carbon) particles will glow orange in the flame.

In a candle flame, the air comes up from the bottom.

There is complete combustion. The flame is hot and has a blue colour.

Further up in the flame, there is less oxygen, because it has already been used up, and the temperature is lower.

Unburned carbon particles (soot) will glow orange in the flame.

You can see the same effect in the burning match.

Serenity Allen · Answer

undefined The color of a flame is determined by the specific elements or compounds present in the burning material.

Avery Adams · Answer

undefined The color of a flame is primarily determined by the chemical composition of the material being burned and the temperature of the flame. Different elements and compounds emit characteristic colors when they burn due to the excitation and subsequent relaxation of electrons in their atomic or molecular structure. This process is known as emission spectroscopy. For example:

- Sodium compounds produce a bright yellow flame.
- Potassium compounds produce a lilac flame.
- Copper compounds produce a blue-green flame.
- Lithium compounds produce a crimson flame.
- Calcium compounds produce an orange-red flame.

The temperature of the flame also plays a role in determining its color. Generally, hotter flames appear bluish-white, while cooler flames tend to be more yellow or orange in color. This is because higher temperatures lead to greater excitation of electrons, resulting in the emission of shorter-wavelength light, which appears bluer.

In summary, the color of a flame is caused by the emission of light from excited electrons in the atoms or molecules of the burning material, with different elements and compounds producing characteristic colors. Additionally, the temperature of the flame influences its color, with higher temperatures generally resulting in bluer flames.