Balancing Chemical Equations

Transcription

1 Lesson Created by: Lauryn Atwood Length of lesson: 1 week Description of the class: Heterogeneous Name of course: Chemistry Grade level: Honors or regular: Regular Balancing Chemical Equations Source of the lesson: ngworksheet/balancingworksheet.htm TEKS addressed: 3.2 (H) The student uses scientific methods to solve investigative questions. The student is expected to organize, analyze, evaluate, make inferences, and predict trends from data. 3.2 (I) The student uses scientific methods to solve investigative questions. The student is expected to communicate valid conclusions supported by the data through methods such as lab reports, labeled drawings, graphs, journals, summaries, oral reports, and technology-based reports. 3.8 (D) The student can quantify the changes that occur during chemical reactions. The student is expected to use the law of conservation of mass to write and balance chemical equations. I. Overview In this lesson, students will balance equations dealing with money in order to become familiar with the logic of balancing. They will then practice balancing chemical equations, using similar techniques. Students will receive a set of balanced equations and create their own categories to classify them in. From this, they will explore the different types of balanced equations, using a jigsaw activity, where they will combine in new groups and have the opportunity to teach explored information to their group members. Groups will then study a new type of chemical reaction and discover its real-life applications. The lesson will end with presentations to the class of the real-life applications. II. Performance or learner outcomes Students will be able to: Identify balanced equations. Classify balanced equations into categories. Demonstrate how to balance equations. Identify types of chemical reactions. Understand the time to use each of the types of chemical reactions. III. Resources, materials and supplies needed 20 balanced chemical equations cut up and in envelopes per group Access to a computer with internet per group IV. Supplementary materials, handouts. (Also address any safety issues Concerning equipment used) Warm-ups and exit slips, Chemical equation booklets,presentation rubric V. Safety Issues None VI. Accommodations for learners with special needs (ELLs, Special Ed, 504, G&T) ELLs, Special Ed, 504: Fill in the blank notes. G&T: Lesson Extensions

2 Five-E Organization Teacher Does Probing Questions Student Does Engage: Learning Experience(s) Critical questions that will establish prior knowledge and Expected Student Responses/Misconceptions create a need to know [Balancing Money] If I went to a bank and handed the teller a $100 bill and asked for change in $20 bills, what can I expect to receive? Five $20 bills. Everyone take out a sheet of paper and write down any amount of money between $10 and $100. Next, write down how many dollar bills and/or coins you could have to make up this total. For example, $100 = five $5 bills, three $10 bills, two $20 bills, and twenty quarters. Call on a few students to share responses. Now pass your paper to another person at your table. When you receive this person s paper, check their answer, then write down another possibility for their total. Call on a few students to share responses. Similar to money, chemical equations can be balanced. We will be exploring how different substances react physically and chemically. In what other ways can I receive change for a $100 bill? Two $50 bills; ten $10 bills; five $10 bills and one $50 bill; etc. Approx. Time 20 mins Evaluation(Decision Point Assessment): Explore: Learning Experience(s) [Balancing Chemical Equations] The assessment you will use to determine what to do next. Critical questions that will allow you to decide whether students understand or are able to carry out the assigned task (formative) What student outcome will indicate that you should move on to the exploration? What will you do if the outcome is something else? Expected Student Responses/Misconceptions

3 Now, let s balance a couple of equations. With the money, we had to figure out how to make different amounts with different types of bills. With chemical equations, we try to make the numbers of atoms on the left equal the numbers on the right. Write HCl + NaOH H 2 O + NaCl on the board. Keep in mind that on the left of the arrow, you have the reactants, which are substances that react to create the products, on the right hand side of the arrow, or what is created. With money, what did we have to keep equal? In chemical equations, what does the arrow mean? The dollar amount. A reaction happens. Create a t-chart under the equation for left and right sides of the arrow. Write H on the board in each column, and fill in the blanks with 2 after students answer the questions. Fill in the rest of the chart doing the same for Na, Cl, and O. [Classifying Balanced Equations] Next, let s balance some equations. Similarly, substances can In this equation, how many hydrogen atoms are on the left side? How many hydrogen atoms are on the right side? How do you know that this equation is already balanced? If 20 students took off one shoe and put it in a pile, what is one way we could organize them? 2 2 All of the atoms on the left equal the number of atoms on the right. Size, color, shape, type, etc.

4 react in a number of ways, which we can categorize. Your group will receive a set of reactions and you will create categories and classify the equations. For each category, you must include a reasonable title and explanation. Pass out a set of 20 balanced chemical equations to each group of 3-4 students. While students are working: Approx. Time 25 mins Evaluation(Decision Point Assessment): Balancing Equations Exit Slip Explain: Learning Experience(s) Why did you organize them like this? What do the numbers in front of the compounds mean? Do you notice any patterns? What do you notice about the numbers of atoms on the left and the numbers of atoms on the right of the arrow? The assessment you will use to determine what to do next. Critical questions that will allow you to help students There are two compounds combining to make one; one compound makes two; etc. Misconception: How many there are [be sure that students understand that the coefficients represent the ratios of compounds in the reaction] In this [double displacement] reaction, the atoms are switched around and partner with the other They are equal What student outcome will indicate that you should move on to the explanation? What will you do if the outcome is something else? Correctly balanced equations and a good explanation of how the equations were balanced would indicate that the class can move forward to the explanation. If not, then the next class day s warm up will be more intensive than a review, until students feel comfortable with balancing the equations. Expected Student Responses/Misconceptions

5 [Investigation: Balanced Equations] Write Al + O 2 Al 2 O 3 on the board. [Aluminum oxide is used to produce aluminum metal] This type of reaction is called a synthesis reaction. In a synthesis reaction, two or more substances combine to make a new compound, which contains the original atoms from the combined substances. In this equation, let s make a general equation. There are six main types of chemical equations that we are going to be talking about today. These include synthesis, decomposition, single displacement, double displacement, acid-base, and combustion. Split students into 5 groups, one for each remaining reaction. In your groups, explore your specific reaction and fill out the page for your specific reaction in your Chemical Equations Booklet. clarify their understanding and introduce information related to concepts to be learned Based on your categories of chemical equations, how is this equation classified? Why? What do you think a synthesis reaction is? How is this equation balanced? If carbon is now the variable A and sulfur is now the variable B, how is a synthesis reaction generalized? Various responses. Students will most likely respond along the lines of this being a combination reaction, where two substances combine to make another. A reaction where something is synthesized/created. 4 aluminum atoms, 3 O 2 compounds, 2 Al 2 O 3 compounds A + B AB

6 You will include a list of compounds involved in your reaction (ex. H and O, for H2 + ½O2 H2O), the basic format of the reaction (ex. A + BX AX + B), and the conditions for which the reaction works (ex the attraction between A and X is stronger than that of B and X). After you and your group learn this set of equations, you will split up and become experts in a larger group, where you will share what you have learned so that everyone else can learn your reaction type. Have students get back into the groups they were in when they classified the balanced equations. Re-classify these equations into their correct categories. Approx. Time 45 mins Evaluation(Decision Point Assessment) Quiz: Balancing Equations Quiz Question: How do your classifications of balanced equations compare to the actual categories of equations? Explain/justify why these categories are sufficient for each reaction type? How do your categories compare? If you had a category that is not similar to the ones we studied, what is it, and how can you justify it? The assessment you will use to determine what to do next. Various responses. Have the class discuss whether or not these categories could be valid. What student outcome will indicate that you should move on to the extension? What will you do if the outcome is something else? The quiz will help familiarize students with balancing equations even more from the day before. This can also be used as a warm up if students didn t do well the day before. The question is useful for students to reflect on their work. They have the chance to assess the categories they created and justify why the balanced equations are separated in the categories that they are. If the outcome is

7 Extend / Elaborate: Learning Experience(s) Critical questions that will allow you to decide whether students can extend conceptual connections in new situations not sufficient, the posters and booklets will solidify the content. Expected Student Responses/Misconceptions Let s talk about synthesis reactions together. Hydrogen and oxygen do form to make water. However, oxygen is unstable as a single atom, so an oxygen molecule is necessary to create water. Write H2 + O2 H2O on the board and have a student balance the equation. Each of the reactions we discussed has a real-life application. Today, we are going to explore these to become more familiar with them and to see how abundant they are in our everyday lives. Split students into the same groups they were in to explore the specific reaction types. Give each group a different reaction type than they had before. In your groups, explore how these reactions are found in real life. Each person in your group must have one reaction from real life. Use this website for your explorations: act.htm What might be an example of a synthesis reaction? How might the formation of water, H 2 O, be a synthesis reaction? Watch for the misconception that adding any two substances can create a new one. This is characteristic of chemical changes in general, not necessarily of synthesis reactions. Two hydrogen atoms and one oxygen atom could collide.

8 Create a PowerPoint slide about this type of reaction. Your group will then present these findings to the class. Everyone will be able to see how your reactions are useful and where/when they occur. Approx. Time 45 mins Evaluation(Decision Point Assessment): Students will be evaluated during their presentations based on their group visuals. Evaluate: Lesson Objective(s) Learned (WRAP UP at end) -> Summarize Go through the PowerPoint submitted by students, having each group present. Students will be evaluated during their presentations based on their group visuals. Students will turn in their completed Chemical Reactions Booklets. The students will note the types of reactions and list the reactions that pertain to their topic of interest. This will be due one week after the completion of the Benchmark/Investigation. Approx. Time 45 mins The assessment you will use to determine what to do next. Critical questions that will allow you to decide whether students understood main lesson objectives What student outcome will indicate that you should move on to the final evaluation? What will you do if the outcome is something else? The PowerPoints will include information from their booklets, as well as real life applications of the equation types they have found. If the PowerPoint slides are insufficient, give students feedback and the option for revisions. Expected Student Responses/Misconceptions

9 Name: Balancing Equations Exit Slip Balance the following equation. CO 2 + H 2 O C 6 H 12 O 6 + O 2 In your own words, explain how you balanced the equation. What chemical process does this equation represent? Name: Balancing Equations Quiz Balance the following equations: Give each reaction type: 1. Hg + O 2 --> HgO 2. Ag 2 O --> Ag + O 2 3. Ba(OH) 2 + H 3 PO 4 --> BaHPO 4 + H 2 O 4. C 3 H 8 + O 2 --> CO 2 + H 2 O 5. Fe + Cl 2 --> FeCl3 Name: Chemical Reaction Types Quiz/Warm Up Provide 3 types of chemical reactions and an example of a balanced equation for each. Types of Chemical Reactions Example of a balanced equation for each reaction

10 Chemical Equations Booklet Page 1 Name: Synthesis Reactions List 2 examples of formulas for this reaction. Using A, B, X, and Y for variables, what is the basic format of the reaction? A + B AB When is this type of reaction likely to happen? (Think on a molecular level!) Everyday Life Examples: Include at least 3 examples, giving both the chemical formula and an explanation of what is happening.

11 Chemical Equations Booklet Page 2 Decomposition Reactions List 2 examples of formulas for this reaction. Using A, B, X, and Y for variables, what is the basic format of the reaction? (For example, A + B AB, for a Synthesis Reaction) When is this type of reaction likely to happen? (Think on a molecular level!) Everyday Life Examples: Include at least 3 examples, giving both the chemical formula and an explanation of what is happening.

12 Chemical Equations Booklet Page 3 Single Displacement Reactions List 2 examples of formulas for this reaction. Using A, B, X, and Y for variables, what is the basic format of the reaction? (For example, A + B AB, for a Synthesis Reaction) When is this type of reaction likely to happen? (Think on a molecular level!) Everyday Life Examples: Include at least 3 examples, giving both the chemical formula and an explanation of what is happening.

13 Chemical Equations Booklet Page 4 Double Displacement Reactions List 2 examples of formulas for this reaction. Using A, B, X, and Y for variables, what is the basic format of the reaction? (For example, A + B AB, for a Synthesis Reaction) When is this type of reaction likely to happen? (Think on a molecular level!) Everyday Life Examples: Include at least 3 examples, giving both the chemical formula and an explanation of what is happening.

14 Chemical Equations Booklet Page 5 Acid-Base Reactions List 2 examples of formulas for this reaction. Using A, B, X, and Y for variables, what is the basic format of the reaction? (For example, A + B AB, for a Synthesis Reaction) When is this type of reaction likely to happen? (Think on a molecular level!) Everyday Life Examples: Include at least 3 examples, giving both the chemical formula and an explanation of what is happening.

15 Chemical Equations Booklet Page 6 Combustion Reactions List 2 examples of formulas for this reaction. Using A, B, X, and Y for variables, what is the basic format of the reaction? (For example, A + B AB, for a Synthesis Reaction) When is this type of reaction likely to happen? (Think on a molecular level!) Everyday Life Examples: Include at least 3 examples, giving both the chemical formula and an explanation of what is happening.

16 Oral Presentation Rubric : Balancing Equations Teacher Name: Ms. Atwood Student Name: CATEGORY Collaboration with Peers Content Almost always listens to, shares with, and supports the efforts of others in the group. Tries to keep people working well together. Shows a full understanding of the assigned chemical reaction. Usually listens to, shares with, and supports the efforts of others in the group. Does not cause "waves" in the group. Shows a good understanding of parts of the assigned chemical reaction. Often listens to, shares with, and supports the efforts of others in the group but sometimes is not a good team member. Does not seem to understand the assigned chemical reaction very well. Rarely listens to, shares with, and supports the efforts of others in the group. Often is not a good team member. Does not provide any input in regards to the assigned chemical reaction. Real-World Example Listens to Other Presentations Provides a thorough understanding of a real-world example for the assigned chemical reaction and gives a balanced chemical equation. Listens intently. Does not make distracting noises or movements. Provides a real-world example for the assigned chemical reaction and gives a balanced chemical equation. Full understanding may be questionable. Listens intently but has one distracting noise or movement. Provides a real-world example for the assigned chemical reaction OR gives a chemical equation that may not be balanced. Sometimes does not appear to be listening but is not distracting. Does not provide a real-world example for the assigned chemical reaction, nor gives a balanced chemical equation. Sometimes does not appear to be listening and has distracting noises or movements.