Is burning a chemical or physical change? Explain your answer.

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Burning, or combustion, is a chemical change, and one of the most dramatic to observe. A chemical change happens when the molecular structure of a substance changes in a way that cannot be reversed. When a substance burns, its molecular bonds are broken down, and it becomes a different substance....

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Burning, or combustion, is a chemical change, and one of the most dramatic to observe. A chemical change happens when the molecular structure of a substance changes in a way that cannot be reversed. When a substance burns, its molecular bonds are broken down, and it becomes a different substance. When one burns carbon compounds, for example, new chemicals are produced—including (depending on the amount of oxygen present) carbon dioxide and carbon monoxide. When wood is burned, it is reduced to ash, and gases escape. The fact that combustion gives off heat and light in addition to changing the chemical composition of the fuel is another indicator that it is a chemical change. Also, (as mentioned above) unlike a physical change, a chemical change cannot be undone. If water freezes, it can be thawed, and, conversely, running water can be frozen. If a piece of firewood burns into ashes, these ashes cannot be reformed into wood.

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