Compare and contrast the properties of charcoal and carbon dioxide.

Incomplete combustion of carbon occurs if enough air is not available to convert all of it to carbon dioxide, and in such as case carbon monoxide is formed by the addition of half the amount of oxygen as is present in carbon dioxide, to the carbon atom, namely, CO instead of CO2.

Explanation:

- "the choice that is not an indicator of a chemical change is "state of matter changes". more common than not, chemical reactions produce energy in the form of light or heat. along with energy, they also produce a new substance called the product that could be in any state of matter (solid, gas, or liquid)."

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.