What is a pure substance?Pure substances are composed of one type of particlePure substances have fixed physical and chemical propertiesPure substances are either elements OR compounds Gold is a pure substance. The surrounding rock is a mixture of different elements and compounds.
MATTER NO Can it be physically separated? mixtures pure substances Can it be chemically decomposed? YES NO elementConcept Map compound
Review: What are chemical elements?Elements are pure substances composed of only ONEtype of atom. Aluminum Bromine Sodium
There are approximately 117 known elements of whichonly 88 occur naturally. Each element has its ownsymbol. Elements are organized on the periodic table. Gold (Au) A Kaboom Key Concept! An element is a pure substance composed entirely of one type of atom!
A closer look at elements Elements are substances composed of one type of atom. For example, helium gas (He), is composed of individual helium atoms. Some elements, like hydrogen gas (H2), are composed of diatomic molecules. Each molecule consists of two hydrogen atoms that are chemically bonded together. What are the other elements that exist as diatomic molecules?
ELEMENTS THAT EXIST AS DIATOMIC MOLECULES Remember: BrINClHOF or the super 7 Individually, these elements only exist as PAIRS of atoms. When these elements combine in reactions to make compounds, they are no longer elements so they do not need to be in pairs!
What is a compound?are pure substancescomposed of TWO or more elementsatoms held together by chemical bondscan only be broken apart or formed by a chemical reactionSodium chloride Water Glucose
What happens in a chemical reaction?reactants are converted to productsbonds are first brokenatoms are rearrangednew bonds form to make different compounds
This unit is all about the types of bonds that holdatoms together to form compoundsionic bonds incompounds likesodium chloridecovalent bonds incompounds likeglucose
AssignmentFIND 5 substances in your home that are chemicalcompounds.