What is an open system in chemistry

Which best describes how johannes kepler developed his laws of planetary motion

What natural processes produce large quantities of co2

Some familiar products contain some of the same types of atoms. for instance, the chemical formula for baking soda is nahco 3. the chemical formula for liquid bleach is naclo, and the chemical formula for table salt is nacl. which choice best describes why these three products have some of the same types of atoms in common?