Can the level of molecular attraction for any ONE substance change? A) No. It's always the same
B) Yes. It changes with the amount of energy.
C) No. Molecular attraction is the same for all substances.
D) Yes. It changes with the freedom of movement.

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

Why is it important for scientists to review and repeat the work of other scientists? 1.a scientific theory must be tested three times before it is proven. 2.the scientific method only applies to repeated experiments. 3.an experiment may have had errors that the scientists didn't recognize. 4.the results of individual scientists may be influenced by bias. 5.an experiment must be performed twice before the data can be analyzed.

2.38g of black copper (ii) oxide is completely reduced by hydrogen to give copper and water. what are the masses of copper and water formed? ?