When you were dropping the water onto the penny, why was the water not spilling off the penny?

Which of the following is a testable hypothesis? a. if i brush my teeth, i will get fewer cavities than if i don't brush my teeth. b. green toothpaste tastes better than blue toothpaste or red toothpaste. c. smart, careful, healthy people always brush their teeth. d. it's wrong to not brush your teeth before you have an important conversation with someone.

What are the spectator ions in 2h+ + so42- + ca2+ + 2r → caso4 + 2h+ + 21?

How many moles of air are there in a human lung with a volume of 2.4 l at stp? explain your answer