A is formed when are held together by attractive forces. A. chemical bond; protons
B. chemical bond; atoms
C. physical bond; protons
D. physical bond; atoms

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.

Compare and contrast physical changes with chemical changes.

Three alkali metals in group 1 are a. calcium, strontium, barium b. boron, aluminum, gallium c. sodium, potassium, rubidium d. fluorine, iodine, chlorine