2 Properties and Changes in Matter - Observing Chemical ChangeProperties and Changes in MatterMatter can undergo both physical change and chemical change.
3 Properties and Changes of Matter - Observing Chemical ChangeAsking QuestionsProperties and Changes of MatterQuestionAnswerWhat are physical properties of matter?Physical properties are characteristics that can be observed without changing one substance into another.What is the evidence for chemical reactions?The evidence for chemical reactions is the formation of new substances and changes in energy.
4 Chemical Reactions Rearrange atoms Involve changes in energy Exothermic: release energy (heat, fire, fizz, etc)Endothermic: absorb energy (drop in temp.)
5 Evidence of Chemical Changes ClueExampleDescriptionColor changeBread dough bakingChangesfromwhite tobrownSmellEggs rottingSmellsbadNew matter createdWood burningWoodchangestoashGas createdBaking soda added to vinegarCreatescarbondioxidegasHeat or Light createdFireworksBurningchemicalscreate lightand heatCut along dotted lines and paste into your science notebook.
6 Properties and Changes in Matter - Observing Chemical ChangeProperties and Changes in MatterChemical changes occur when bonds break and new bonds form.
7 Describing Chemical Reactions Cellular phone messages make use of symbols and abbreviations to express ideas in shorter form. Similarly, chemists often use chemical equations in place of words.
8 What Are Chemical Equations? - Describing Chemical ReactionsWhat Are Chemical Equations?Chemical equations use chemical formulas and other symbols instead of words to summarize a reaction.The arrow symbol is read YIELDS which means “results in” or “produces”
9 Chemical Equations ___ CH4 + ___ O2 ___CO2 + ___ H2O methane and oxygen yield carbon dioxide and water___ CH4 + ___ O ___CO2 + ___ H2OReactantsProductsThe molecules that combine are called REACTANTS and the molecules that result are called PRODUCTS
10 - Describing Chemical Reactions Chemical FormulasThe formula of a compound identifies the elements in the compound and the ratios in which their atoms are present.
11 - Describing Chemical Reactions Conservation of MassThe principle of conservation of mass states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products.
12 Balancing Chemical Equations - Describing Chemical ReactionsBalancing Chemical EquationsTo describe a reaction accurately, a chemical equation must show the same number of each type of atom on both sides of the equation.
13 Balancing Chemical Equations - Describing Chemical ReactionsBalancing Chemical EquationsMagnesium metal (Mg) reacts with oxygen gas (O2), forming magnesium oxide (MgO). To write a balanced equation for this reaction, first write the equation using the formulas of the reactants and products, then count the number of atoms of each element.
14 Balancing Chemical Equations - Describing Chemical ReactionsBalancing Chemical EquationsBalancing Chemical Equations:Balance the equation for the reaction of sodium metal (Na) with oxygen gas (O2), forming sodium oxide (Na2O).
15 Balancing Chemical Equations - Describing Chemical ReactionsBalancing Chemical EquationsBalancing Chemical Equations:Balance the equation for the reaction of tin (Sn) with chlorine gas (Cl2), forming tin chloride (SnCl2).
16 Classifying Chemical Reactions - Describing Chemical ReactionsMany chemical reactions can be classified in one of three categories: synthesis, decomposition, or replacement.
17 A + B → AB AB → A + B AB + C → AC + B AB + CD → AC + BD Chemical ReactionsType of ReactionDefinition EquationSynthesisDecompositionSingle ReplacementDouble ReplacementTwo or more elements or compounds combine to make a more complex substanceA + B → ABAB → A + BCompounds break downinto simpler substancesOccurs when one element replaces another one in a compoundAB + C → AC + BOccurs when different atoms in two different compounds trade placesAB + CD → AC + BDA = Red B = Blue C = Green D = Yellow
18 Identifying Chemical Reactions Use the code below to classify each reaction.S = Synthesis D = Decomposition SR = Single Replacement DR = Double Replacement____ P O2 → P4O10 ____ Mg O2 → MgO____ HgO → Hg O2 ____ Al2O3 → Al O2____ Cl NaBr → NaCl Br2 ____ CuCl H2S → CuS HCl
19 Building Vocabulary - Describing Chemical Reactions Key Terms: Examples:closed systemcoefficientsynthesisdecompositionKey Terms:Key Terms:Examples:replacementExamples:chemical equationA chemical equation is a short, easy way to show a chemical reaction.In a closed system, matter is not allowed to enter or leave.Replacement is the process in which one element replaces another in a compound or two elements in different compounds trade places.reactantA coefficient is a number in a chemical equation telling you how many atoms or molecules of a reactant or product take part in the reaction.A substance you have at the beginning of a reaction is a reactant.productA new substance produced in a reaction is a product.conservation of massConservation of mass means that during a chemical reaction, matter is not created or destroyed.Synthesis means combining two or more elements or compounds to make a more complex substance.open systemDecomposition means breaking down compounds into simpler products.In an open system, matter can enter from or escape to the surroundings.