Question

what observation about baking powder suggests that it is a mixture of substances?

Explanation:

Baking powder can produce gas when reacting with moisture or an acid, indicating multiple components. One common component is a carbonate (like sodium bicarbonate) which reacts with an acid component (like cream - of - tartar or monocalcium phosphate) and water to release carbon dioxide gas. This reactivity implies it is a mixture of substances.

Answer:

It produces gas when reacting with moisture or an acid, indicating multiple components that react together.