2 Symbols Chemists use chemical symbols to represent elements Chemical Symbol: 1st 1-2 letters of the name of the element1st letter is always Capitalized2nd letter is always lower caseExamples: Co = Cobalt; O = Oxygen;Be = BeryliumException: Some use the letters from the Latin nameExamples: Fe = Iron (Ferrum)K = Potassium (Kalium)Cu = Copper (Cuprium)
3 Formulas Chemists use chemical formulas to represent compounds Compounds: 2 or more elementsExamples: NaCl = Sodium ChlorideH2O = Water
4 Breaking upCompounds can be broken down into simpler substances by chemical means, but elements cannotChemical changes can be used to break down the substancesHeating sugar can be heated until it breaks down into solid carbon and water vapor
5 “Heating sugar can be heated until it breaks down into solid carbon and water vapor” Do you think either of those substances that are formed can be broken down any?Yes, the water can be broken down into hydrogen and oxygen
6 PropertiesProperties of compounds differ greatly from the properties of the individual elements that make them upSolid sodium is extremely reactiveChlorine is a gasCombined they make up sodium chloride, aka table salt
9 Classifying mixturesA mixture is a physical blend of two or more componentsBased on the distribution of the components, mixtures can be classified as heterogeneous or homogeneous mixtures
10 Heterogeneous mixture: a mixture in which the composition is not uniform throughout Ex: oil and vinegar, sand in waterHomogeneous mixture: a mixture in which the composition is uniform throughoutAlso known as a solution
11 Homogeneous mixturesMany solutions are liquid, but can also be gas (air) or solids (stainless steel)The term “phase” can be used to describe any part of a sample with uniform composition and propertiesHomogeneous mixtures have 1 phase
14 Separating mixturesDifferent physical properties can be used to separate mixturesDifferent BPs or MPs can be usedFiltration: separates a solid from a liquidCoffee filters separate grounds from waterDistillation: a liquid is boiled to produce a vapor then condensed into a liquid
17 Chemical reactionsChemical changes are signs of chemical reactions happeningIron reacting with oxygen to form rustFe + O2 Fe2O3During a chemical reaction, the composition of matter always changes
18 A substance produced in the reaction is the “product” Fe + O2 Fe2O3A substance present at the start of a chemical reaction is called a “reactant”A substance produced in the reaction is the “product”Reactants react to produce products
19 Recognizing chemical reactions Signs a reaction may have occurred:Production of gas or bubblesChange in colorChange in temperaturePrecipitate formsA solid that forms and settles out of a liquid mixture
20 Law of Conservation of Mass During any chemical reaction or physical change, the mass of the products is always equal to the mass of the reactantsBottom line: you cannot create or destroy matter. Matter is conserved.
21 DiscussWhat about burning a candle? Where does the mass go??
22 Review questions How are mixtures classified? Come up with a way to separate a mixture of sand and saltHow is a compound different from an element?How much water would form if 4.8 grams of hydrogen reacted with 38.4 g oxygen?