The energy evolved when magnesium burns in air is in the form of

Step 1: Analyze the question We are asked what forms of energy are given out when magnesium burns in air.

Step 2: The concept Burning (combustion) of a metal in oxygen is an exothermic reaction. The energy released depends on what you actually observe during the reaction.

Step 3: Observations when magnesium burns Magnesium ribbon burns in air with a dazzling white flame (light). The reaction also releases a lot of heat. The product is a white powder, magnesium oxide:

2Mg(s) + O₂(g) → 2MgO(s) + energy (heat and light)

There is no noticeable sound, as there would be in an explosion or the "pop" test for hydrogen.

Step 4: Evaluate the options

• A. Heat only: incomplete, because the bright light is the most obvious feature.
• B. Heat and sound: wrong, since no sound is produced.
• C. Light and heat: correct, matching the bright white flame and the heat given off.
• D. Sound: wrong.

**Answer: C. Light and heat.

Exam tip: Remember "Mg burns with a bright white light" and always link it to the formation of white MgO ash. Whenever you see magnesium burning, think "light + heat." Hydrogen's "pop" is the one to associate with sound.