Question

1. which type of property cannot be observed without changing the composition of a substance?

Explanation:

In chemistry (a subfield of Natural Science), we have two main types of properties: physical and chemical. Physical properties (like color, density, melting point) can be observed without changing the substance's composition. Chemical properties, however, describe a substance's ability to undergo a chemical change (like reactivity, flammability), which requires a change in the substance's composition (i.e., a chemical reaction) to be observed. So the property that can't be observed without changing the substance's composition is a chemical property.

Answer:

Chemical property