When an element is heated, the electrons of each atom become excited and produce energy. Different elements create energy of different wavelengths when they burn. By watching the colors in a flame, you can identify what is being burned. This is useful for diagnosing problems with gas appliances and identifying impurities in the gas supply.
Both lithium and strontium produce a red flame when they burn. However, the strontium flame is brighter red. Red flames have the least amount of energy and have the lowest temperature.
Orange and Yellow
Calcium burns with an orange flame. Sodium burns bright yellow. A yellow tip is normal on a propane flame. A natural gas flame that has a lot of yellow indicates that there is not enough air in the mixture.
A number of elements generate flames in the green spectrum. Barium and molybdenum produce yellowish-green flames. Boron creates a bright green flame. Thallium burns pure green. Phosphorus and zinc burn bluish green.
Selenium, indium and arsenic burn blue. A normal natural gas --- methane --- flame also burns solid blue.
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