I think the correct answer would be the third option. From the physical change that happened, we can only tell that the mass of the plastic would be still the same and would weigh 15 grams. This is in accordance with the Law of conservation of mass where it states that mass cannot be destroyed or created. So, since it is only a physical change that happens the substance itself would still be the same and it is only the form that is changed, it would still have the same mass. However, with the change, the volume is changed and is said to increase which means it would greatly affect the density. Increasing the volume would result to a decrease in density.
Answer:
it represents the numner of protons in an atoms nucleus
