Pls help me I don’t understand it’s for my science class. Plz check if correct and tell me wether each is element or compound

Why does a plastic bottle that is sealed at a high altitude change it’s shape when taken to lower altitude

The comparison of the number of atoms in a copper coin the size of a penny with the number of people on earth is made to illustrate which of the following? a. that atoms are indivisible b. that atoms are very small c. that atoms are very large d. that in a copper penny, there is one atom for every person on earth

Which of the following substances is the most soluble in water? a. sodium chloride b. methane c. bromine d. carbon