Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chemical Equations and Reactions You should be able to - classify reactions by type - write a balanced molecular equation Chemical reactions Chemical equations - balancing equations - law of conservation of mass Chemical equations - synthesis decomposition single replacement double replacement combustion Signs of Chemical Reactions There are five main signs that indicate a chemical reaction has taken place: release input change in color change in odor production of new gases or vapor https://www.youtube.com/watch?v=JSiBSSFKRwE input or release of energy difficult to reverse Illinois State University, Jeff Christopherson; 2002 Chemical Equations aluminum oxide Depict the kind of reactants and products and their relative amounts in a reaction. 4 Al(s) + 3 O2(g) reactant 2 Al2O3(s) product The letters (s), (g), and (l) are the physical states of compounds. The numbers in the front are called stoichiometric coefficients. Chemical Equations 4 Al(s) + 3 O2(g) 2 Al2O3(s) 4 g Al + 3 g O2 yield 2 g Al2O3 This equation means: 4 Al atoms + 3 O2 molecules yield 2 molecules of Al2O3 or 4 Al moles + 3 O2 moles yield 2 moles of Al2O3 Chemical Equations Because the same atoms are present in a reaction at the beginning (reactants)and at the end (products), the amount of mass in a system does not change. The Law of Conservation of Mass 100% Kotz web Chemical Factory 100% Chemical Equations Because of the principle of the conservation of mass, An equation must be balanced. It must have the same number of atoms of the same kind on both sides. Lavoisier, 1788 Chemical Equations methane + oxygen carbon dioxide Reactant CH4 + 2 O2 + water Product CO2 + 2 H2O Unbalanced and Balanced Equations H Cl Cl H H H H Cl H2 + Cl2 → HCl (unbalanced) reactants H Cl 2 2 H H Cl Cl Cl H2 + Cl2 → 2 HCl (balanced) reactants products 1 1 Cl H Cl 2 2 products 2 2 Steps for Balancing Chemical Equations 1. Write skeleton equation 2. Count the atoms of each element in the reactants. *Remember polyatomic ions 3. Count the atoms of each element in the products. 4. Add coefficients so that you have the same number of atoms of each element on both sides. 5. Write coefficients in their lowest possible ratio. General Chemical Equation ● Use letters of the alphabet (A,B,C,D) in place of chemical symbols for elements to provide basic structure for each type of reaction Ex: A + B → AB instead of: H2 + O2 → H2O (skeleton equation) Activity: General Equation Dance Task: 1. In groups, read the section of the textbook related to your group’s assigned chemical reaction. 2. Come up with a short dance/representation of that type of reaction based on their general chemical equation. 3. Present to your peers. Types of chemical equations 1. Synthesis 2. Decomposition 3. Single displacement 4. Double displacement 5. Combustion Inspirational Video 1.Synthesis ● A + B → AB ● Two elements combine to form a compound ● Can be: ○ metal + non-metal ○ non-metal + non-metal ex: H2 + O2 → 2H2O 2H2 + 2O2 → 2H2O 2. Decomposition ● AB → A + B ● A compound is broken apart into two or more elements or simpler compounds. ● Products can be: ○ metal + nonmetal ○ non-metal + non-metal ● Opposite of synthesis ● ex: H2O → H2 + O2 2H2O → 2H2 + O2 3. Combustion Chemical or compound reacts quickly with oxygen gas usually a hydrocarbon give off heat and light CxHy + O2 → H2O ex: + O2 → CO+2 + O CHCH CO 2HH22O 4 + 42O2 → 2 4. Single Displacement AB +C → CB + A Element reacts with ionic compound Element kicks out part of the ionic compound The elements that switch places must be either two metals or two non-metals 3CuCl → AlCl AlCl22 ++ CU 3Cu ex: CuCl2 2++2Al Al → 5. Double Displacement AB + CD → AD + CB The positive or negative ions in two dissolved ionic compounds switch places ex: Mg(OH)2 + AgNO3 → Mg(NO3)2 + AgOH Mg(OH)2 + 2AgNO3 → Mg(NO3)2 + 2AgOH Additional Resources for Review Khan Academy- Balancing Chemical Equations https://goo.gl/3eje5L