What phase change is a type of. physical change, chemical change, nuclear change, covalent change

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.

Which statement accurately describes the relationship between air pressure, air density, or altitude? as altitude increases, pressure increases. as altitude increases, air density increases. air pressure and density are lowest at sea level. denser air exerts more pressure than less dense air.

Write the chemical symbols for three different atoms or atomic cations with 27 electrons. asap!