Is a Spanish omelette mixture or pure substance?

A Spanish omelette is a mixture.

Here's why:

* Multiple Ingredients: It's made from eggs, potatoes, onions (often), and sometimes other ingredients like peppers or chorizo.

* No Chemical Bonding: The ingredients are not chemically bonded together. They are simply mixed and cooked together.

* Individual Properties: Each ingredient retains its own properties in the omelette. You can still taste the individual flavors of the eggs, potatoes, and onions.

Therefore, a Spanish omelette is a heterogeneous mixture.