Student Exploration Balancing Chemical Equations

Student Exploration: Balancing Chemical Equations Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Vocabulary: coefficient, combustion, compound, decomposition, double replacement, element, molecule, product, reactant, single replacement, subscript, synthesis Prior Knowledge Questions (Do these BEFORE using the Gizmo.) The scouts are making s’mores out of toasted marshmallows, chocolate, and graham crackers. 1. What is wrong with the image below? there isnt enough of each item to equal 4 2. Assuming a s’more requires two graham crackers, one marshmallow, and one piece of chocolate, how many s’mores could you make with the ingredients shown? two Gizmo Warm-up In a chemical reaction, reactants interact to form products. This process is summarized by a chemical equation. In the Balancing Chemical Equations Gizmo, look at the floating molecules below the initial reaction: H2 + O2 ฀ H2O. 1. How many atoms are in a hydrogen molecule (H2)? 2 2. How many atoms are in an oxygen molecule (O2)? 2 3. How many hydrogen and oxygen atoms are in a water molecule (H2O)? 3 4. In general, what does a subscript (such as the “2” in H2) tell you about the molecule? how many atoms it has 5. A chemical equation is balanced if the number of each type of atom on the left side is equal to the number of each type on the right side. Is this reaction balanced? Get the Gizmo ready: Activity A: ● Check that the Synthesis reaction is selected and that all coefficients are set to one. (The coefficients are the numbers in the boxes.) Balancing equations Introduction: The equation H2 + O2 ฀ H2O is unbalanced because there are two oxygen atoms on the reactants side of the equation, and only one on the products side of the equation. To balance the equation, you cannot change the structure of any of the molecules, but you can change the number of molecules that are used. Question: How are chemical equations balanced? 1. Balance: Turn on Show histograms. The equation is balanced when there are equal numbers of each type of atom represented on each side of the equation. In the Gizmo, use the up and down arrows to adjust the numbers of hydrogen, oxygen, and water molecules until the equation is balanced. When you are done, turn on Show summary to check your answer. Write the balanced equation here: 4 H2 + 2 O2 ฀ 4 H2O 2. Solve: Turn off Show summary. Use the Choose reaction drop down menu to see other equations, and balance them. Check your answers and then write the balanced equations. 2 Al + 6 HCl ฀ 2 AlCl3 + 3 H2 6 NaCl ฀ 6 Na + 3 Cl2 3 Na2S + 6 HCl ฀ 6 NaCl + 3 H2S 1 CH4 + 2 O2 ฀ 1 CO2 + 2 H2O 3. Practice: Balance the following chemical equations. (These equations are not in the Gizmo.) A. 2 Na + 1 Cl2 ฀ 2 NaCl B. 2 Na + 2 H2O ฀ 4 NaOH + C. 2 Mg + 1 O2 ฀ 2 MgO D. 2 KClO3 ฀ 2 KCl + 3 O2 E. 4 Al + 6 CuO ฀ 2 F. 1 I2 + 4 Na2S2O3 ฀ 2 1 H2 Al2O3 + 6 Cu NaI + 2 Na2S4O6 G. 6 Activity B: Mg + 1 P4 ฀ 2 Mg3P2 Get the Gizmo ready: Classifying reactions ● Turn off Show summary and Show histograms. Introduction: Chemical equations show how compounds and elements react with one another. An element is a substance consisting of one kind of atom, such as aluminum (Al) or oxygen gas (O2). A compound is a substance made of more than one kind of atom, such as water (H2O) or table salt (NaCl). Question: How are chemical reactions classified? 1. Match: Most chemical reactions can be classified as one of four types. Using the chemical equations in the Gizmo as a guide, match the following definitions to the type of reaction. e One reactant is broken down into two or more products. A. Synthesis b A fuel is combined with oxygen to produce carbon dioxide and water. B. Decomposition a Two or more reactants combine to form one product. C. Single replacement d Two compounds react to form two different compounds. D. Double replacement c A compound reacts with an element to form a new compound and a different element. E. Combustion 2. Practice: Balance each of the chemical equations below. (Some equations may already be in balance.) In the space to the right, classify the reaction as a synthesis, decomposition, single replacement, or double replacement reaction. A. 1 AgNO3 + 1 KCl ฀ 1 AgCl + 1 B. 1 H2O + 1 SO3 ฀ 1 H2SO4 synthe sis KNO3 double replac ement I2 C. 2 KI + 1 Cl2 ฀ 2 KCl + 1 single replac ement D. 2 NaHCO3 ฀ 1 Na2CO3 + 1 H2O + 1 CO2 decom positio n H2 E. 1 Zn + 2 HCl ฀ 1 ZnCl2 + 1 single replace ment F. 1 BaCl2 + 1 Na2SO4 ฀ 1 BaSO4 + 2 NaCl double displac ement G. 1 C 3H 8 + 5 O2 ฀ 3 CO2 + 4 H2O combu stion H. 2 Al + 3 CuCl2 ฀ 2 AlCl3 + 3 Cu single displac ement