An experiment applies heat to a substance and produces a gas that is a new and different substance. choose the true statement.
a. this represents a physical change only.
b. this represents a chemical change only.
c. this represents both a physical and a chemical change.
d. this represents neither a physical change nor a chemical change.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.