Achange occurs when a substance changes phase.
physical
chemical
nuclear

A physical change occurs when a substance changes phase.

For example, boiling pure water (H₂O) is physical change of substance (from liquid to gaseous state). In physical change, the bonds between oxygen and hydrogen can not be separated.

Sublimation of iodine (from solid to gas state) is also physical change.

Physical property can be observed and measured without any changes in molecular composition. The same substance is present before and after the change.

the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.