The amount of matter in a given amount of space is known as the

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?

Which description best characterizes the motion of particles in a solid?

Consider the story you just read. all but one of the choices below indicate that something is living.