Chemical Reactions Conservation of Matter

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1 Chemical Reactions

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3 Chemical Reactions Teacher Pages Purpose The purpose of this station is to reinforce students ability to compare and analyze the rearrangement of atoms in a chemical reaction. Students will create and use models to show this rearrangement and how it demonstrates conservation of matter. Essential Understandings! The total number and type of atoms does not change in a chemical reaction.! Mass is conserved in a chemical reaction.! The rearrangement of the atoms in a chemical reaction results in new substances with new properties. Materials Container of vinegar Box of baking soda Beaker Graduated cylinder Plastic spoon or Scoopula Weigh paper, if desired Metric balance Atom tiles Colored pencils (3 different colors) The following materials are included in the blackline masters for this station. Station Information Sheet Atom Tile Stickers Advance Preparation 1. Print one copy of all the blackline masters for this station using a color printer. Color is essential to the station activities. Make one copy of the Student Pages (including the glossary) for each student. 2. Laminate the Station Information Sheet and a Periodic Table of Elements. 3. Obtain 20 board game tiles, such as Scrabble tiles. Teacher Pages 1

4 Chemical Reactions: Middle School Physical Science Formative Assessments 4. Print a copy of the Atom Tile Stickers onto sticker paper. Cut out the atom stickers and apply them to the tiles. Use 20 tiles labeled as follows: 5 labeled C, 6 labeled H, 6 labeled O and 3 labeled Na. There will be more tiles than students need. Station Setup 1. Tape the Station Information Sheet to the station table. Students will use this to confirm the station is set up correctly. 2. Set out the atom tiles, ensuring there are 20 tiles: 5 carbon 6 oxygen 6 hydrogen 3 sodium 3. Place the balance, vinegar, baking soda, and plastic spoon or Scoopula at the station. Procedures 1. Tell students to check the station setup against the Station Information Sheet when they arrive at the table. If anything is missing or out of place, they should notify you. 2. Pass out a copy of the Student Pages to each student. Instruct students to work through the procedures and answer the questions with their teammates. 3. As students work through the station activity, circulate around the room, checking their work and responding to questions. Guide to Student Responses Note The suggested student responses presented below in italics represent the best possible answers to the student questions; actual student responses may vary. Essential Question How does the arrangement of atoms in hydrogen gas and oxygen gas change when they react to form liquid water as shown in the following equation? 2H 2 + O 2 " 2H 2O Before the reaction, hydrogen is bonded to itself and oxygen is bonded to itself. The atoms of hydrogen and oxygen rearrange and become bonded to each other when they react to form liquid water. Teacher Pages 2

5 Middle School Physical Science Formative Assessments Chemical Reactions: Procedure 1. Using the supplies at your table, mix 20 ml of vinegar and 5 grams of baking soda in the beaker. Observe what happens during this chemical reaction and fill out the table below using the information that follows. The balanced chemical equation for this reaction looks like this: Baking soda + vinegar " sodium acetate + water + carbon dioxide HC 2H 3O 2 + NaHCO 3 " NaC 2H 3O 2 + H 2O + CO 2 Reactants: Count the number of atoms of each element in the baking soda (NaHCO 3) and in the vinegar (HC 2H 3O 2). Write the totals on the chart below in the Reactants column. Products: Count the number of atoms of each element in the sodium acetate (NaC 2H 3O 2), in the water (H 2O), and in the carbon dioxide (CO 2). Write the totals on the chart in the Products column. Number of atoms of each element Atoms Reactants Products carbon 3 3 hydrogen 5 5 oxygen 5 5 sodium 1 1 Total What do you notice about the total number of atoms in the Reactants column as compared to the total number of atoms in the Products column for each element involved in this reaction? What does this tell you about what happens to atoms during a chemical reaction? The number and type of atoms in the Reactants column is the same as in the Products column. This indicates that no matter is created or destroyed during the reaction. Teacher Pages 3

6 Chemical Reactions: Middle School Physical Science Formative Assessments 3. Choose the correct number of atom tiles equal to the type and amount in your Reactants column. Assemble the baking soda molecule as pictured below. Now use the remaining tiles to assemble the vinegar molecule. Draw this in the space provided. Be sure to indicate the chemical symbols and color your drawings with the colored pencils. Baking soda tiles Vinegar tiles drawing 4. Gather all the tiles from the baking soda and vinegar arrangements. Place the tiles on the metric balance and record the mass. Mass of model reactants = grams [Answers will vary depending on the type of tiles.] 5. Using the same tiles, assemble the sodium acetate, water, and carbon dioxide models. Draw these in the spaces provided. Be sure to indicate the chemical symbols and lightly color your drawings with the colored pencils. Teacher Pages 4

7 Middle School Physical Science Formative Assessments Chemical Reactions: Sodium acetate tiles Water tiles Carbon dioxide tiles 6. Gather all the tiles from the sodium acetate, water, and carbon dioxide tile arrangements. Place all the tiles on the metric balance and record the mass. Mass of model products = grams [Answers should equal the mass found in number 4 but will vary depending on the type of tiles.] 7. Based on the work you have just completed, explain how your measurements support the Law of Conservation of Mass. The Law of Conservation of Mass states that in chemical reactions, the mass of the products equals the mass of the reactants. The mass of the reactants was equal to the mass of the products. 8. The same 20 tiles were used in each part of this activity. How does this support the Law of? Matter cannot be created or destroyed. The number and type of atoms in the reactants is the same as the number and type of the products. The same number and type of atom tiles in both the reactants and the products were used. Electricity is passed through a sample of water producing 4 g of hydrogen and 32 g of oxygen. Teacher Pages 5

8 Chemical Reactions: Middle School Physical Science Formative Assessments 9. How many grams of water reacted in order to obtain the results described above? The sample of water has a mass of 36 g because the mass of the reactants must equal the mass of the products. The products were 4 g of hydrogen and 32 g of oxygen and when added together equal 36 g. 10. How do the properties of the products (hydrogen and oxygen) compare with the reactant (water)? Water is a colorless, odorless liquid at room temperature while hydrogen is a colorless, flammable gas, and oxygen is a colorless, odorless gas. Teacher Pages 6

9 Middle School Physical Science Formative Assessments Chemical Reactions: In photosynthesis, plants use energy in sunlight to make glucose and release oxygen by rearranging the atoms of carbon dioxide and water. Here is a word equation for the chemical reaction for photosynthesis: Six molecules of carbon dioxide plus six molecules of water yield one molecule of glucose and six molecules of oxygen. The chemical equation looks like this when it is represented with chemical formulas: 11. How many carbon atoms are needed for this reaction? Explain your answer. 6 carbon atoms are needed because there are 6 in the reactants (in the carbon dioxide) and 6 in the products (in the glucose). 12. How does the arrangement of carbon atoms change during photosynthesis? The carbon atoms are bonded to oxygen only in the reactants forming carbon dioxide. The carbon atoms are rearranged and bonded to hydrogen and oxygen in the products of the reaction. 13. How were the oxygen atoms rearranged after photosynthesis? The carbon dioxide molecules contained 12 oxygen atoms, and there were 6 oxygen atoms in the water molecules before photosynthesis. After photosynthesis, 6 oxygen atoms became part of the glucose molecule and the remaining 12 oxygen atoms formed the oxygen molecules. Teacher Pages 7

10 Chemical Reactions: Middle School Physical Science Formative Assessments 14. Now that you have completed these exercises, return to the Essential Question. Would you like to modify or change your answer? Write any modifications to your answer below. Answers will vary. Teacher Pages 8

11 Blackline Masters Chemical Reactions Blackline Masters 1

12 Chemical Reactions: Middle School Physical Science Formative Assessments 2 Blackline Masters

13 Middle School Physical Science Formative Assessments Chemical Reactions: Atom Tile Stickers Blackline Masters 3

14 Chemical Reactions: Middle School Physical Science Formative Assessments Station Information Sheet for Chemical Reactions: 4 Blackline Masters

15 Chemical Reactions Student Pages Purpose The purpose of this station is to reinforce your ability to compare and analyze the rearrangement of atoms in a chemical reaction. You will create and use models to show this rearrangement and how it demonstrates conservation of matter. Materials Metric balance Container of vinegar Box of baking soda Beaker Plastic spoon or Scoopula Graduated cylinder Atom tiles Colored pencils (3 different colors) Essential Question How does the arrangement of atoms in hydrogen gas and oxygen gas change when they react to form liquid water as shown in the following equation? 2H 2 + O 2! 2H 2 O Student Pages 1

16 Chemical Reactions: Middle School Physical Science Formative Assessments Procedure 1. Using the supplies at your table, mix 20 ml of vinegar and 5 grams of baking soda in the beaker. Observe what happens during this chemical reaction and fill out the table below using the information that follows. The balanced chemical equation for this reaction looks like this: Baking soda + vinegar! sodium acetate + water + carbon dioxide HC 2 H 3 O 2 + NaHCO 3! NaC 2 H 3 O 2 + H 2 O + CO 2 Reactants: Count the number of atoms of each element in the baking soda (NaHCO 3 ) and in the vinegar (HC 2 H 3 O 2 ). Write the totals on the chart below in the reactant column. Products: Count the number of atoms of each element in the sodium acetate (NaC 2 H 3 O 2 ), in the water (H 2 O) and in the carbon dioxide (CO 2 ). Write the totals on the chart in the products column. Number of atoms of each element Atoms Reactants Products carbon hydrogen oxygen sodium Total Dispose of used vinegar and baking soda according to your teacher s instructions. Student Pages 2

17 Middle School Physical Science Formative Assessments Chemical Reactions: 2. What do you notice about the total number of atoms in the Reactants column as compared to the total number of atoms in the Products column for each element involved in this reaction? What does this tell you about what happens to atoms during a chemical reaction? 3. Choose the correct number of atom tiles equal to the type and amount in your Reactants column. Assemble the baking soda molecule as pictured below. Now use the remaining tiles to assemble the vinegar molecule. Draw this in the space provided. Be sure to indicate the chemical symbols and color your drawings with the colored pencils. Baking soda tiles Vinegar tiles drawing 4. Gather all the tiles from the baking soda and vinegar arrangements. Place the tiles on the metric balance and record the mass. Mass of model reactants = grams Student Pages 3

18 Chemical Reactions: Middle School Physical Science Formative Assessments 5. Using the same tiles, assemble the sodium acetate, water, and carbon dioxide models. Draw these in the spaces provided. Be sure to indicate the chemical symbols and lightly color your drawings with the colored pencils. Sodium acetate tiles Water tiles Carbon dioxide tiles 6. Gather all the tiles from the sodium acetate, water, and carbon dioxide tile arrangements. Place the tiles on the metric balance and record the mass. Mass of model products = grams 7. Based on the work you have just completed, explain how your measurements support the Law of Conservation of Mass. 8. The same 20 tiles were used in each part of this activity. How does this support the Law of? Student Pages 4

19 Middle School Physical Science Formative Assessments Chemical Reactions: Electricity is passed through sample of water producing in 4g of hydrogen gas and 32g of oxygen gas. 9. How many grams of water reacted in order to obtain the results described above? 10. How do the properties of the products (hydrogen and oxygen) compare with the reactant (water)? Student Pages 5

20 Chemical Reactions: Middle School Physical Science Formative Assessments In photosynthesis, plants use energy in sunlight to make glucose and oxygen from carbon dioxide and water. Here is a word equation for the chemical reaction for photosynthesis: Six molecules of carbon dioxide plus six molecules of water yield one molecule of glucose and six molecules of oxygen. The chemical equation looks like this when it is represented with chemical formulas: 11. How many carbon atoms are needed for this reaction? Explain your answer. 12. How does the arrangement of carbon atoms change during photosynthesis? Student Pages 6

21 Middle School Physical Science Formative Assessments Chemical Reactions: 13. How were the oxygen atoms rearranged after photosynthesis? 14. Now that you have completed these exercises, return to the Essential Question. Would you like to modify or change your answer? Write any modifications to your answer below. NOTE: Because other students are going to do the activity after you, be sure to put all the materials at the station back as you found them. Sometimes there will be materials that need to be renewed or replaced. If you need assistance or have any questions, ask your teacher. Student Pages 7

22 Chemical Reactions: Middle School Physical Science Formative Assessments I Need to Remember... Complete this part after class discussion of this station. I need to remember... Student Pages 8

23 Middle School Physical Science Formative Assessments Chemical Reactions: Glossary for Chemical Reactions: Atom An atom is the smallest unit of matter that keeps all of the properties of an element. Chemical Equation A chemical equation uses symbols to show reactants on the left of a reaction arrow and products on the right. In all chemical processes, matter is neither created nor destroyed, but instead simply changes in form. Element An element is a pure substance that cannot be broken into smaller parts using chemical changes. Molecule A molecule is the smallest group of atoms bonded together to form a pure substance that has properties different from the elements forming it. Product Products are the materials that form as the result of a chemical reaction. Reactants Reactants are the materials that enter into a chemical reaction. Student Pages 9

24 Chemical Reactions: Middle School Physical Science Formative Assessments Student Pages 10