Answer:
It is a chemical change
Explanation:
Fat is a triglyceride. Triglycerides form soap when they come into contact with sodium hydroxide.
Now, we know that a chemical change is one in which a new substance is formed and it is not easily reversible. Heat is also given out or absorbed in the process.
Now the combination of sodium hydroxide and fat yields a new substance called soap. The appearance of the new substance conclusively proves that a chemical change has taken place.