Scientists are studying how substance a and substance b react. when substance a and b are mixed, a substance different from a and b floats to the top of the solution. this is evidence that a(n) question 6 options: a. chemical change occurred. b. irreversible change occurred. c. endothermic change occurred. d. physical change occurred.

This is evidence that a. a chemical change occurred.

Substances A and B must have changed into the new substance with new properties. That’s a chemical change.

The reaction could be reversible (A + B ⇌ product) or irreversible (A + B → product). WE can’t tell just by looking at the reaction.

The question didn’t say whether heat was absorbed or evolved, so we don’t know if the reaction is endothermic or exothermic.

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.