What visual evidence shows that combustion reactions release energy?

Answer: Fire.

Explanation: Combustion reactions combust. Through combustion, they release heat and light energy in the form of fire.

A combustion reaction is a major class of chemical reactions, commonly referred to as "burning." In the most general sense, combustion involves a reaction between any combustible material and an oxidizer to form an oxidized product. It usually occurs when a hydrocarbon reacts with oxygen to produce carbon dioxide and water. Good signs that you're dealing with a combustion reaction include the presence of oxygen as a reactant and carbon dioxide, water, and heat as products. Inorganic combustion reactions might not form all of those products but remain recognizable by the reaction of oxygen.