How do you determine the number of moles in a sample

Which best describes the present-day universe? opaque, expanding very slowly, stars produce heavy elements transparent, expanding at an accelerated rate, stars produce heavy elements opaque, expanding at an accelerated rate, stars produce only hydrogen and helium transparent, expanding very slowly, stars produce only hydrogen and helium

Match the term to its description match term definition chemical energy a) internal energy caused by vibrations of atoms and molecules electrical energy b) electromagnetic energy that travels in waves radiant energy c) the movement of an electrical charge thermal energy d) potential energy stored in the bonds between atoms

Consider the lewis structure for ch4 methane is this molecule polar or nonpolar