What type of property requires a reaction with another substance to be observed?

A chemical property is defined as a characteristic of a substance that can only be observed during a chemical reaction, which involves a change in the composition or identity of the substance. This contrasts with physical properties, which can be observed without the substance undergoing any change in its chemical makeup.

For example, when you burn wood, it reacts with oxygen in the air, producing smoke and ash, thus demonstrating a chemical property—the ability to combust. In this case, to truly see the wood’s chemical properties, you must initiate a reaction that alters its substance.

Physical properties, on the other hand, include characteristics such as color, odor, melting point, and density, which can be observed or measured without altering the substance's chemical structure. Electrical and thermal properties relate to how substances interact with electric fields or temperatures but do not inherently involve a reaction between substances within the same context as chemical properties do.