COMPOUNDS AND MIXTURES Lesson 11 Notes

Elements combine with other elements Over 100 known elements. Elements are pure substances and can’t be separated by physical means Most substances in the world are not just 1 elements Elements combine in different ways to form new substances /molecules

CHEMICAL FORMULAS A chemical formula is a group of chemical symbols and numbers ( in subscript) that show the type and number of atoms in a molecule. If there is no number then it is just 1 atom Example: OH ( 1 oxygen and 1 hydrogen)

COMPOUNDS Pure substances that are formed when 2 or more DIFFERENT ELEMENTS join together chemically (bond) Example: 2 H and 1 O = H20 (water) Example: 1 Na and 1 Cl = NaCl (salt) Example: 6 C and 12 H and 6 O = C6H12O6 (glucose) Example: 2 Fe and 3 O = Fe2O3 (iron oxide , rust)

COMPOUNDS Are new substances that are made up of one kind of a new molecule Molecules are groups of 2 or more atoms held together by very strong chemical bonds. Bonds form when atoms share or give away(transfer) valence electrons Example: rust is no longer iron or oxygen, it is a new substance called rust

COMPOUNDS ARE NEW SUBSTANCES The properties of compounds are different than the properties of the elements that make them up Example: H2O liquid at room temp where H and O are gases at room temp Water doesn’t burn but H does

Mixtures Are combinations of 2 or more substances that are not joined chemically Mixtures are not pure substances The parts of the mixture keep their own identities and properties – they DON’T MAKE NEW SUBSTANCES Example: sugar and salt mixed together Sugar still sweet, salt still salty

MIXTURES CAN BE SEPARATED BY PHYSICAL PROPERTIES Physical properties can be used to separate mixtures Particle size ( large, medium, small – filter with different sized filters) Texture (fine, smooth, rough) Density ( sinks if more than water or floats if less than water) Solubility( dissolves in water) Boiling point(evaporate) Attracted to magnet