Students are trying to identify an element that has many of the same physical and chemical properties as sodium (Na) but a larger atomic mass. Which of the following elements could the students be investigating?

Which is a chemical property of iron? a. it forms iron oxide (rust) when exposed to moisture and air. b. it is a gray–black metal that is hard to the touch. c. it has a melting point of 2795°f (1536°c). d. it is a good conductor of heat

As air becomes more dense, (select all that apply) o. air weighs less o. gas molecules are closer together o. air is colder o. air weighs more o. gas molecules are further apart o. air is hotter

The biosphere of the earth is made up of what compound? organic or inorganic?