- Defining matter - Earth as four spheres - Organic and inorganic compounds
Matter is defined as anything that occupies space and has mass. Matter is made of tiny pieces called atoms. Atoms are basic building blocks of all matter. There are 94 naturally-occurring types of atoms in nature. Atoms are made up of protons, neutrons and electrons.
Molecules consist of two or more atoms. Compounds consist of two or more different types of atoms that are bonded. Oxygen gas, for example, consists of two bonded oxygen atoms. This makes it a molecule, but not a compound.
The Earth can be seen as a system of four spheres that interact with each other - atmosphere, hydrosphere, lithosphere and biosphere. Atmosphere is the thin layer of gases including water vapor that separate the Earth from outer space. Hydrosphere is water in all its liquid and solid forms.
Lithosphere consists of all the other elements required by living organisms such as minerals to survive. Biosphere consist of living systems. Human beings, plant life and animal life all exist in the biosphere and require the other three spheres to survive and thrive.
Organic compounds are chemical compounds in living organisms that bond to form complex molecules. Chemical compounds in the human body contain six elements - carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur.
Inorganic compounds are chemical compounds that do not have carbon-carbon or carbon-hydrogen bonds.
Living organisms require elements essential to life - carbon, hydrogen and oxygen to survive.