A skillet is lined with a thin layer of cooking oil followed by a layer of unpopped popcorn kernels. Upon heating the kernels all pop thereby escaping the skillet. Which of the following physical and/or chemical changes occurred?

Physical change.

Explanation:

This is a physical change.The reason for escaping pops is the water caught internal parts it's bit.Inside the event that the bit is warmed to a tall satisfactory temperature, this water will modify into steam. Due to the troublesome and for the preeminent parcel nonporous shell, the steam has no put to go, coming nearly in a buildup of weight internal parts the bit.Once the weight gets tall satisfactory and the temperature comes to around 180 degrees Celsius (355 degrees Fahrenheit), the pops escape from the skillet or bursts and the popcorn is turned internal parts out.

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.