Why do we fill balloons with helium gas instead of oxygen gas

An occluded front moves over the farmland that has been experiencing drought conditions. what change in weather will this front likely bring? a. gray skies, but no rain b. an extended period of rain c. more dry air and sunny skies d. violent, short-lived thunderstorms

Zoe is investigating the composition of substance a, an unknown substance. using chemical processes, she analyzes substance a and determines it is composed of sodium, oxygen, and hydrogen atoms in a ratio of 1 : 1 : 1. what is substance a? a. a compound b. an element c. a heterogeneous mixture d. a homogeneous mixture

The three types is stress that act on earths rocks are compression, tension, and