Chapter 6-Chemistry in Biology COMPOSITION OF MATTER -Matter-everything in universe is composed of matter. -Matter is anything that occupies space or has mass -Mass-quantity of matter in an object -Weight-pull of gravity on us ELEMENTS -Pure substances that cannot be broken down chemically into simpler kinds of matter -More than 100 elements (92 naturally occuring) -90% of the mass of an organism is composed of 4 elements (oxygen, carbon, hydrogen, and nitrogen) -Each element has a unique chemical symbol -Consists of 1-2 letters -First letter is always captialized ATOMS -The simplest particle of an elemetnt that remains all the properties of that element. -Properties of atoms determine the structure and properties of the matter they compose.