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Name: ________________________ Physical Science: Guided Notes CHAPTER 21 PRICE Chapter 21: Chemical Equations Section 1: Chemical Change What is a chemical reaction? A. Describing a chemical reaction 1. ____________________ Reactions- change of one or more substances converted into new substances 2. Reactants - substances that __________________ or change 3. __________________- new substances that are produced Produce: Reactants ---- __________________ B. Conservation of Mass 1. Conservation of _____________-a law which states that, in a chemical reaction, ___________ is not created or ______________; it stays the ___________ 2. Antione Lavoisier – _________________ of Modern Chemistry 1. Found mass of __________________ equaled the mass of the reactants C. Writing Equations 1. Chemical _______________ - uses chemical _________________ and _________________ to describe a chemical reaction and the products it produces 2. ______________________ formula - expresses the ____________________ between elements in the compounds and molecules they make up 3. _____________________ used to show physical state of reactants; (s) _______________ (aq) aqueous (g) _________ (l) liquid 4. _______________________ – whole numbers in ____________ of the symbol, which represent the number of ______________ of each substance in a reaction **Located before the symbols 5. __________________________ – small lowered numbers which represent the number of atoms in a molecule of a particular element *Located after and _____________ the symbols 6. Nomenclature – way to name things scientifically Discussion Questions 1. What does the law of conservation of mass state? 2. What is the function of coefficients in a chemical equation? Section 2: Chemical Equations: Checking for Balance 1. A _________________ chemical reaction- both sides of equation have the ___________ number of atoms of each element 2. Coefficients are used in _____________ of the element or compound to balance. 3. Choosing coefficients - becomes _____________ with practice; trial and error at first Writing balanced chemical equations - 4 step process 1. ____________ the reaction in words 2. Write the equation using _________________ and symbols 3. Check for ______________ 4. Add ________________ where needed for balance Discussion Question Why do chemical equations need to be balanced? Section 3: Classifying Chemical Reactions Types of Reactions: 1. _________________ Reaction- two or ___________ substance form a new substance A + B --> AB 2. Decomposition Reaction-One substance _________________ down into two or more substances AB ---> A + B 3. __________________-displacement Reaction- one element _______________ another one in a compound; A + BC ---> AC +B or D + BC --> BD + C 4. Double-displacement Reaction- results if a ______________________, water, or a gas forms when ___________ ionic compounds in a solution are combined; AB + CD --> AD + CB 5. Combustion Reaction-a substance ___________________ with oxygen to produce energy “X” + O2 --> CO2 + H2O 1 Oxidation-Reduction (Redox) These reactions often involve oxygen _________________________ Loss of electrons Substance ________________ “oxidized” Reduction Gain of _________________ Substance becomes “reduced” Discussion Questions 1. What two chemical reactions are “opposites” of each other and why? 2. What are the 5 types of chemical reactions? Section 4: Chemical Reactions and Energy Chemical Reactions ______________________ energy exchange ___________________-Breaking chemical bonds release energy Endergonic-Forming chemical bonds requires _______________ ____________________-Chemical Reaction where energy is primarily given ____________ in the form of heat Endothermic-Chemical reaction that _________________ heat energy in order to proceed B. More energy out 1. A catalyst speeds up a chemical reaction without itself being permanetly changed 2. An inhibitor prevents or slows a chemical reaction or interferes with the catalyst’s action DISCUSSION QUESTIONS: How are chemical bonds involved in energy exchanges? 2