What happens to the mass of a substance during a physical change?

Frictional forces acting on an object are often converted into energy, which causes the temperature of the object to rise slightly.

The characteristic of two different types of reactions are shown below. reaction a: electrons are gained by the atoms of an element. reaction b: protons are lost by the atom of and element. which statement is true about the atoms of the elements that participate in the two reactions? a: their identity changes in both reaction a and b. b: their identity changes in reaction a but not b. c: their identity changes in reaction b but not a. d: their identity remains the same.

Which of these expressions are correct variations of the combined gas law? p1v1t2 = p2v2t1 both