How many molecules of O2 are there in 2.0 moles of oxygen?

Compare and contrast physical changes with chemical changes.

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

Which fossil fuel is mainly used for heating and cooking? a. electricity b. coal c. petroleum d. natural gas