Conservation of Mass
IPC HS/Science Unit: 04 Lesson: 01 Suggested Duration: 5 days
Conservation of Mass
Lesson
Synopsis: In this lesson, students will explore the concept that mass is conserved when substances undergo chemical change and that the number and kind of atoms are the same in the reactants and products. In addition, they will recognize valence electrons and that the behavior of valence electrons is responsible for chemical changes. Students will plan and implement an investigation to demonstrate their understanding of the law of conservation of mass.
TEKS: I.7 I.7B I.7C
Science concepts. The student knows that changes in matter affect everyday life. The student is expected to: Recognize that chemical changes can occur when substances react to form different substances and that these interactions are largely determined by the valence electrons. Demonstrate that mass is conserved when substances undergo chemical change and that the number and kind of atoms are the same in the reactants and products.
Scientific Process TEKS: I.2 I.2E ©2012, TESCCC
Scientific processes. The student uses scientific methods during laboratory and field investigations. The student is expected to: Communicate valid conclusions.
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IPC HS Science Unit: 04 Lesson: 01
GETTING READY FOR INSTRUCTION Performance Indicator(s): • Select a balanced equation from a laboratory investigation. Use the balanced equation to explain and demonstrate the law of conservation of mass. Present information in a diagram, and explain, in writing, how the balanced equation represents a chemical change. Demonstrate that the number and kind of atoms are the same in the reactants and products. (I.2E; I.7C) 1C, 1E; 5G
Key Understandings and Guiding Questions: • Matter and mass are conserved in chemical reactions. •
— In what ways is it helpful to know that the mass before and after a reaction is constant? — What information can a chemical equation relay? The law of conservation of mass applies only to a closed system. — What is a closed system? — Why does the law of conservation of mass apply only to closed systems? — How does the law of conservation of mass apply to chemical reactions?
Vocabulary of Instruction: • law of conservation of • coefficient • chemical equation
© 2012, TESCCC
• • •
yield sign reactants products
08/22/12
• •
subscript valence electrons
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IPC HS/Science Unit: 04 Lesson: 01
Materials: Refer to Notes for Teacher section for materials.
Attachments: • Handout: Balancing Equations Practice Sheet (1 per student) • Teacher Resource: Balancing Equations Practice Sheet KEY • Handout: Law of Conservation of Mass • Teacher Resource: Law of Conservation of Mass KEY • Teacher Resource: Baggie Fun Station Cards (see Advance Preparation, 1 per •
station) Teacher Resource: Evaluate Instructions PI (1 for projection)
Advance Preparation: 1. Prior to Day 1, create a classroom set of resealable, plastic bags containing two different colors of gumdrops. The first set will have only one gumdrop to represent hydrogen and one gumdrop to represent oxygen. The second set will have two gumdrops joined together with toothpicks representing oxygen molecules, and the third set will have two gumdrops joined together with toothpicks representing hydrogen molecules. The fourth set will have additional gumdrops available for students to use in modeling. You will need a class set of each of the four types of bags, with one bag per pair of students. 2. Prior to Day 3, gather materials for and prepare resealable, plastic bags from the Teacher Resource: Baggie Fun Station Cards. Students will participate in only one of the five stations, so you will have two sets of the five stations. The class will be divided into ten groups. Prepare enough materials at each station for all class rotations. Predetermine if any students have nut allergies. 3. Prepare attachment(s) as necessary.
Background Information: During this lesson, students demonstrate that mass is conserved when substances undergo chemical change and the number and kinds of atoms are the same in the reactants and products. In addition, they recognize valence electrons, and how the behavior of valence electrons is responsible for chemical changes. In this lesson, students will also be learning about synthesis, decomposition, combustion, double replacement, and single replacement reactions.
GETTING READY FOR INSTRUCTION SUPPLEMENTAL PLANNING DOCUMENT Instructors are encouraged to supplement and substitute resources, materials, and activities to differentiate instruction to address the needs of learners. The Exemplar Lessons are one approach to teaching and reaching the Performance Indicators and Specificity in the Instructional Focus Document for this unit. Instructors are encouraged to create original lessons using the Content Creator in the Tools Tab located at the top of the page. All originally authored lessons can be saved in the “My CSCOPE” Tab within the “My Content” area.
INSTRUCTIONAL PROCEDURES Instructional Procedures
Notes for Teacher
ENGAGE – Conservation of Mass Demonstration
NOTE: 1 Day = 50 minutes Suggested Day 1
©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures 1. Begin the class with a conservation of mass demonstration. Show the students a triple beam balance, a clear bottle with some water in it, a balloon, and an effervescent antacid tablet as shown in Figure 1 (see Instructional Notes).
Notes for Teacher
Materials: • triple beam balance (1 per teach
2. Ask students to draw the setup of the demonstration in their notebooks.
• •
3. Break up an antacid tablet, and place the pieces inside the balloon. Stretch
•
the opening of the balloon over the top of the bottle, being careful not to let the pieces of the tablet fall in to the water.
balloons (1 or more per class)
water bottle (clear, filled with tap water, 1 per teacher) effervescent antacid tablet (1 per class)
Instructional Notes:
4. Place the bottle with water, antacid, and balloon on top of the triple beam balance, and have a student volunteer mass the system as shown in Figures 2 and 3 (see Instructional Notes).
5. Use the same student throughout the demonstration to measure mass at different points during the reaction.
6. Facilitate a class discussion using the following question. Ask: • What do you think will happen when you let the pieces of antacid tablets fall into the water? Will the system with the bottle weigh more or less? Accept all answers at this time. The main question for the class to ponder is whether the bottle apparatus will weigh more, less, or the same while the tablet dissolves and after the tablet dissolves.
7. Manipulate the balloon so that the pieces of antacid fall in without dislodging the balloon. At all points during the process, the mass should not change, other than when the bottle is touched since it is a closed system. (There is nowhere for the mass/gas to go.)
Figure 1 Figure 2 Figure 3 Figure 4
Loughmiller, D. (Photographer) (2012). Demonstratin of conservation of mass [Print].
Check for Understanding: Allowing students to relate a definitio an experience, such as the demonstration, helps to solidify understanding of concepts.
8. Repeat the activity (steps 4 and 5), but this time cut a hole in the balloon. 9. Ask: • •
Can you explain what has happened in both of these situations? Accept all reasonable answers. What is a chemical reaction? (Chemical reactions occur when two chemicals unite or react to form a compound that is unlike the original substances and cannot be changed back to its original form.) Review this definition as needed.
Science Notebooks: Students draw the demonstration set record the definition of the law of conservation of mass, and then write reflection relating the two.
10. After the class has thoroughly discussed what has occurred, project the following definition for the law for the conservation of mass. • The law of conservation of mass states that the mass of a closed system of substances will remain constant, regardless of the processes acting inside the system. An equivalent statement is ©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
that matter cannot be created nor destroyed, although it may change form.
11. Instruct students to copy down the definition in their science notebooks. 12. Ask students to discuss the definition with a partner and relate the parts of the closed system to the demonstration. For example, the closed system was the water bottle, the antacid tablet, the water, and any gas inside.
13. Facilitate a discussion including the following, and ask for volunteers to share their thoughts regarding the demonstration with the class. • The total mass of reactants in a chemical reaction will equal the total mass of the products. • Gases are produced during some chemical reactions and can be forgotten because they cannot be seen. The mass of the gas needs to be calculated and added to the products when determining the final mass of a reaction. Use a plastic bag or a balloon to collect the gas, and then add this mass to the final reaction products. • Remember, mass is not created or destroyed so when balancing a chemical equation, one must make sure that the number of atoms of each of the reactants on the left side of the equation equals the number of atoms of the products on the right side of the equation. Ex. If you have four atoms of oxygen on the reactant side, make sure that you have four on the product side.
14. Instruct students to write a reflection in their notebooks relating the demonstration to the law of conservation of mass.
EXPLORE/EXPLAIN I – Modeling Equations
Suggested Day 2
1. Divide the class into pairs. Distribute a resealable, plastic bag that has one color gumdrop that will represent a single oxygen atom and one color gumdrop that will represent a single hydrogen atom (see Advance Preparation) to each group. Ask: • Does anyone remember the chemical formula for water? Students should remember H2O from middle school. • Can you make a model of water using these two ‘atoms’? (No, because there are not enough “H” gumdrops.) 2. Explain to students that in reality, elemental hydrogen and elemental oxygen are both diatomic, meaning that hydrogen and oxygen are among seven elements (called diatomic) that only exist in nature in pairs. The complete list is H, N, O, F, Cl, Br, and I. 3. Ask: • What is responsible for the behavior of bonding between ©2012, TESCCC
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Materials: • bags of single atom gumdrops (s Advance Preparation, 1 bag per • bags of oxygen molecule gumdro (see Advance Preparation, 1 bag pair) • bags of hydrogen molecule gumdrops (see Advance Preparation, 1 bag per pair) • bags of additional gumdrops (see Advance Preparation, 1 bag per Single hydrogen and oxygen gumdrops page 5 of 12
IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
elements? (Valence electrons. The outermost shell of an atom is called its valence shell. It is the decisive shell during bonding. Only the electrons of this outermost shell are involved during bonding; electrons are either: given away from the outermost shell, accepted into the outermost shell, or shared with the electrons in the outermost shell of another element. This explains the reactivity of elements which may result in chemical reactions.) 4. Collect the first resealable, plastic bag, and distribute two new bags, one that has two gumdrops joined together with toothpicks representing oxygen molecules and the other that has two gumdrops joined together representing hydrogen molecules (see Advance Preparation). Ask: • Can you make a model of a water molecule with these new bags? Accept all answers. 5. Explain that even though there are enough atoms, the answer is still “no” because we would end up with one single oxygen atom, and because hydrogen and oxygen have to be bonded to another element or paired with other atoms, the bonding will not work. Ask: • What number or combination of gumdrops would you need so that hydrogen and oxygen could be paired and end up making one or more water molecules with no atoms left over? This question is intended to get students to reflect. Do not give the answer at this time. 6. Make as many gumdrops available to students as they may need to experiment with the ratios. After a few minutes, ask the question (above) again. Students should arrive at the answer that two pairs of hydrogen gumdrops and one pair of oxygen gumdrops will start off joined, yet still allow them to end up with two water molecules with no atoms left over.
Paired hydrogen and oxygen gumdrops
Loughmiller, D. (Photographer) (2012). Gumdrop ato [Print].
Instructional Notes: There are several websites available do an excellent job of describing the process of balancing equations. Consider mixing such activities in as practice and homework throughout th week.
Writing equations and using subscrip covered in greater depth in chemistry
Misconceptions: • Students may think that a chemic change changes the atoms themselves.
Science Notebooks: Students copy sample equations and label the components in their noteboo
7. Repeat the process with chemical equations you have modeled on the board or projected. Working with a concrete model first should demonstrate to students how electrons work within bonding. 8. Write the following on the board: First Equation H + O H2 O 9. Review with students that the 2 in H2O is called a subscript and represents a pair of hydrogen atoms. The elements or compounds on the left side of the equation are reactants, the ones on the right side are products, and the arrow is a yields sign. Ask for a volunteer to come to the board and count the number of hydrogen atoms on the left side of the equation and then the numbers on the right side of the equation. Repeat ©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
the same task for oxygen. Ask: 1. What is wrong with the equation? (Hydrogen and oxygen elements are not ‘traveling’ in pairs, and there are more hydrogen atoms on the right side of the equation than on the left.) 10. Write the following on the board: Second Equation H2 + O2 H2O 11. Ask:
2. Is this equation correct? (No) Their answer should still be “no” because the number of atoms on both sides still don’t match. 12. Write the correctly balanced equation. Third Equation 2H2 + O2 2H2O 13. Review the fact that we have now added a number, called a coefficient, in front of the letters, which are a chemical symbols. The coefficient carries forward to all elements in the compound. 2H2 + O2
2H2O
2 X H2 = 4H O2 = 2O
2 X H2 = 4H 2 X O = 2O
14. Instruct students to copy down the correct formula and then label the above equation with the terms: subscript, coefficient, reactants, products, and yield. Monitor for correct labeling. 15. Explain that the first equation represents their first bag, the second equation represents the second pair of bags, and the third equation matches their prediction that two pair of hydrogen gumdrops and one pair of oxygen gumdrops would be needed to have an even number of pairs to start with in order to create water molecules (with no “left over” atoms). 16. Point out to students that the last model illustrates the law of conservation of mass. 17. Say:
3. This law states: in a chemical reaction, the mass of the products (what you start with) is equal to the mass of the reactants (what you end with). ©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
18. Facilitate a discussion in which students reflect on the following questions. Ask: 4. How would the law of conservation of mass apply to chemical reactions? (The law of conservation of mass is often applied to basic chemical reactions to explain what happens on an atomic level during a reactionthat every atom present at the start of the reaction is still present at the end of the reaction.) 5. In what ways is it helpful to know that the mass before and after a reaction is constant? Accept appropriate answers. 6. What information can a chemical equation relay? Accept appropriate answers.
ELABORATE I – Balancing Equations Practice
©2012, TESCCC
Suggested Day 2 (continued)
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures 1. Ask students to review their definition of the law of conservation of mass in their notebooks.
2. Ask for student volunteers to restate the law in their own words. Answers will vary, but correct any misconceptions.
3. Inform students that today they will be practicing the balancing of equations, just as they did the previous day with the gumdrops.
4. Distribute the Handout: Balancing Equations Practice Sheet to each student.
5. Model an example problem or two on the board for students, balancing the equation.
6. Ask students to complete the next equation and then stop. 7. Ask for a volunteer to come to the board and show how they completed the problem. Work with the student to clarify, and assist them in completing the problem, if needed.
8. Inform students they will have most of the class to complete the handout, but that the class will discuss the problems during the last 15 minutes of the period.
9. Monitor and assist students as they complete the rest of the problems.
Notes for Teacher Materials: • glue or tape (per group)
Attachments: • Handout: Balancing Equations Practice Sheet (1 per student) • Teacher Resource: Balancing Equations Practice Sheet KEY
Instructional Notes: Exercise sensitivity in calling student work problems on the board. Try to choose volunteers or choose specific students who have correctly answere the problems. One way to do this eas is to walk by students’ desks and ma check mark by correctly completed examples that students will later shar with the class.
Science Notebooks: Students affix correctly completed handouts in their notebooks to use fo later reference.
10. When the majority of students are finished, ask for volunteers to come to the board to show and explain how they worked each problem. Clarify misconceptions, and instruct students to revise their handouts as necessary.
11. Instruct students to affix the handouts in their notebooks. EXPLORE/EXPLAIN II – Law of Conservation of Mass Investigation 1. Inform students they will be completing two activities to demonstrate the law of conservation of mass.
2. Divide the class into groups. 3. Distribute a copy of the Handout: Law of Conservation of Mass. Instruct students to read through the first activity carefully. Address safety precautions and lab cleanup procedures. Answer any questions students may have about the first activity.
4. Monitor and assist students as they complete Activity 1. ©2012, TESCCC
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Suggested Days 3 and 4
Materials: • resealable plastic bag (gallon-siz per group) • cup (small, plastic, 2 per group)
• • •
vinegar (acetic acid, 1 small container per group) baking soda (sodium bicarbonate small container per group) triple beam balance (1 per group page 9 of 12
IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures 5. When groups have completed the first activity, facilitate a discussion in which students share their results and reflect on how the investigation relates to the law of conservation of mass.
6. Instruct students to read through the second activity carefully. Address the steps the groups will use to plan their investigation. Answer any questions they may have regarding the preparation of the plan.
7. Remind students they must have their plan approved before any testing may occur.
8. Monitor and assist groups in planning their investigations and then in completing the investigations.
9. Facilitate a discussion in which each group shares a summary of their procedure and their results. Include the following questions in the discussion: Say/Ask: • The law of conservation of mass applies only to a closed system. • What is a closed system? (A system in which energy or matter is not gained or lost by the system is considered a closed system.) • Why does the law of conservation of mass apply only to closed systems? (Theoretically, nothing in nature is totally isolated and energy or matter may be transferred in or out of a system in many forms, including chemical, heat, and light. Therefore, the law of conservation of mass applies only to closed systems. In this case, nothing is created nor destroyed.)
Notes for Teacher • seltzer tablets (amount will vary p • • • •
group based on student design) flask (1 per group) flask stopper (1 per group) water (per group) safety goggles (1 per student)
Attachments: • Handout: Law of Conservation Mass • Teacher Resource: Law of Conservation of Mass KEY
Safety Notes: Safety goggles must be worn for this activity.
ELABORATE II – Baggie Fun 1. Inform the class that today they will complete an activity and then will be 2. 3.
4.
5.
Suggested Day 4 (continued) Materials: 8. station bags (see Advance sharing their results with the class. Preparation, enough for each gro to have 1 bag, per class per Stati Divide the class into ten groups. You will need to gather materials for two 2-5): sets of the five stations (see Advance Preparation). 9. resealable plastic bags Explain to the students that each group will complete only one station. 10. walnuts in shells Students will have 45 minutes to observe the outcome of their specified 11. ice cubes activity and make as many measurements as they can. hammer (1 per Station 1) beakers (large, 1 per Station 2) Instruct the groups to read the instructions on their station card, complete 14. beakers (small, 4; 2 per Station 4 the investigation, record their observations and set up in their notebooks, per Station 5) and then clean up their station. water (warm, per Station 2) paper towels (1 roll, per Station 2) Remind students to wear their safety goggles throughout the activity. 17. Play-Doh® (large amount, per
©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures 6. Instruct students to have a representative from their group transfer the group's findings to an appropriate table on the board, so that the whole class can see the outcomes of the other groups.
7. Assign a station to each group. Monitor and assist groups as they complete the activity.
8. After the activity is completed, facilitate a discussion in which each group summarizes their activity and their results.
9. Ask: 7. What did each of the activities have in common? The students should find that mass is conserved in all examples.
10. Encourage each group to respond to the question. Clarify any misconceptions, especially if a group’s data doesn’t correlate with the other groups’ data. Look for errors in student procedures, and discuss how retesting could be done.
Notes for Teacher Station 3)
18. weigh paper (several sheets per group at Station 3)
19. water (tap, per Stations 4; warm
Station 5) 20. Epsom Salts™ (250 g minimum, Station 4) 21. sugar (70 g minimum, per Station 22. wooden craft stick (2, 1 per Statio 4 and 5) 23. triple beam balance (1 per station safety goggles (1 per student) Attachments: • Teacher Resource: Baggie Fun Station Cards (see Advance Preparation, 1 per station)
Safety Notes: Predetermine if anyone in your class nut allergies. Safety goggles must be worn for this activity.
Instructional Notes: While these activities may seem simp they reinforce the law of conservation mass.
The law of conservation of mass, als known as the principle of mass/matte conservation, states that the mass of closed system (in the sense of a completely isolated system) will rema constant over time.
This principle is equivalent to the conservation of energy, in the sense when energy or mass is enclosed in system and none is allowed in or out quantity cannot otherwise change. Th mass of an isolated system cannot b changed as a result of processes act inside the system.
The law implies that mass cannot be created or destroyed, although it may ©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
rearranged in space and changed int different types of particles; and for an chemical process in a closed system mass of the reactants must equal the mass of the products. Science Notebooks: Students draw set ups, record observations, and answer questions their science notebooks.
EVALUATE – Performance Indicator - Balanced Equations Performance Indicator • Select a balanced equation from a laboratory investigation. Use the balanced equation to explain and demonstrate the law of conservation of mass. Present information in a diagram, and explain, in writing, how the balanced equation represents a chemical change. Demonstrate that the number and kind of atoms are the same in the reactants and products. (I.2E; I.7C) 1C, 1E; 5G 1. Refer to the Teacher Resource: Evaluate Instructions PI for information on administering the performance assessment.
Suggested Day 5 Attachments: • Handout: Balancing Equations Practice Sheet (previously distributed) • Teacher Resource: Balancing Equations Practice Sheet KEY • Teacher Resource: Evaluate Instructions PI (1 for projection)
Science Notebooks: Students refer to their notes in order complete the assessment. The assessment may be completed in the science notebooks.
©2012, TESCCC
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Conservation of Mass
Lesson
Synopsis: In this lesson, students will explore the concept that mass is conserved when substances undergo chemical change and that the number and kind of atoms are the same in the reactants and products. In addition, they will recognize valence electrons and that the behavior of valence electrons is responsible for chemical changes. Students will plan and implement an investigation to demonstrate their understanding of the law of conservation of mass.
TEKS: I.7 I.7B I.7C
Science concepts. The student knows that changes in matter affect everyday life. The student is expected to: Recognize that chemical changes can occur when substances react to form different substances and that these interactions are largely determined by the valence electrons. Demonstrate that mass is conserved when substances undergo chemical change and that the number and kind of atoms are the same in the reactants and products.
Scientific Process TEKS: I.2 I.2E ©2012, TESCCC
Scientific processes. The student uses scientific methods during laboratory and field investigations. The student is expected to: Communicate valid conclusions.
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IPC HS Science Unit: 04 Lesson: 01
GETTING READY FOR INSTRUCTION Performance Indicator(s): • Select a balanced equation from a laboratory investigation. Use the balanced equation to explain and demonstrate the law of conservation of mass. Present information in a diagram, and explain, in writing, how the balanced equation represents a chemical change. Demonstrate that the number and kind of atoms are the same in the reactants and products. (I.2E; I.7C) 1C, 1E; 5G
Key Understandings and Guiding Questions: • Matter and mass are conserved in chemical reactions. •
— In what ways is it helpful to know that the mass before and after a reaction is constant? — What information can a chemical equation relay? The law of conservation of mass applies only to a closed system. — What is a closed system? — Why does the law of conservation of mass apply only to closed systems? — How does the law of conservation of mass apply to chemical reactions?
Vocabulary of Instruction: • law of conservation of • coefficient • chemical equation
© 2012, TESCCC
• • •
yield sign reactants products
08/22/12
• •
subscript valence electrons
page 2 of 12
IPC HS/Science Unit: 04 Lesson: 01
Materials: Refer to Notes for Teacher section for materials.
Attachments: • Handout: Balancing Equations Practice Sheet (1 per student) • Teacher Resource: Balancing Equations Practice Sheet KEY • Handout: Law of Conservation of Mass • Teacher Resource: Law of Conservation of Mass KEY • Teacher Resource: Baggie Fun Station Cards (see Advance Preparation, 1 per •
station) Teacher Resource: Evaluate Instructions PI (1 for projection)
Advance Preparation: 1. Prior to Day 1, create a classroom set of resealable, plastic bags containing two different colors of gumdrops. The first set will have only one gumdrop to represent hydrogen and one gumdrop to represent oxygen. The second set will have two gumdrops joined together with toothpicks representing oxygen molecules, and the third set will have two gumdrops joined together with toothpicks representing hydrogen molecules. The fourth set will have additional gumdrops available for students to use in modeling. You will need a class set of each of the four types of bags, with one bag per pair of students. 2. Prior to Day 3, gather materials for and prepare resealable, plastic bags from the Teacher Resource: Baggie Fun Station Cards. Students will participate in only one of the five stations, so you will have two sets of the five stations. The class will be divided into ten groups. Prepare enough materials at each station for all class rotations. Predetermine if any students have nut allergies. 3. Prepare attachment(s) as necessary.
Background Information: During this lesson, students demonstrate that mass is conserved when substances undergo chemical change and the number and kinds of atoms are the same in the reactants and products. In addition, they recognize valence electrons, and how the behavior of valence electrons is responsible for chemical changes. In this lesson, students will also be learning about synthesis, decomposition, combustion, double replacement, and single replacement reactions.
GETTING READY FOR INSTRUCTION SUPPLEMENTAL PLANNING DOCUMENT Instructors are encouraged to supplement and substitute resources, materials, and activities to differentiate instruction to address the needs of learners. The Exemplar Lessons are one approach to teaching and reaching the Performance Indicators and Specificity in the Instructional Focus Document for this unit. Instructors are encouraged to create original lessons using the Content Creator in the Tools Tab located at the top of the page. All originally authored lessons can be saved in the “My CSCOPE” Tab within the “My Content” area.
INSTRUCTIONAL PROCEDURES Instructional Procedures
Notes for Teacher
ENGAGE – Conservation of Mass Demonstration
NOTE: 1 Day = 50 minutes Suggested Day 1
©2012, TESCCC
06/12/13
page 3 of 12
IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures 1. Begin the class with a conservation of mass demonstration. Show the students a triple beam balance, a clear bottle with some water in it, a balloon, and an effervescent antacid tablet as shown in Figure 1 (see Instructional Notes).
Notes for Teacher
Materials: • triple beam balance (1 per teach
2. Ask students to draw the setup of the demonstration in their notebooks.
• •
3. Break up an antacid tablet, and place the pieces inside the balloon. Stretch
•
the opening of the balloon over the top of the bottle, being careful not to let the pieces of the tablet fall in to the water.
balloons (1 or more per class)
water bottle (clear, filled with tap water, 1 per teacher) effervescent antacid tablet (1 per class)
Instructional Notes:
4. Place the bottle with water, antacid, and balloon on top of the triple beam balance, and have a student volunteer mass the system as shown in Figures 2 and 3 (see Instructional Notes).
5. Use the same student throughout the demonstration to measure mass at different points during the reaction.
6. Facilitate a class discussion using the following question. Ask: • What do you think will happen when you let the pieces of antacid tablets fall into the water? Will the system with the bottle weigh more or less? Accept all answers at this time. The main question for the class to ponder is whether the bottle apparatus will weigh more, less, or the same while the tablet dissolves and after the tablet dissolves.
7. Manipulate the balloon so that the pieces of antacid fall in without dislodging the balloon. At all points during the process, the mass should not change, other than when the bottle is touched since it is a closed system. (There is nowhere for the mass/gas to go.)
Figure 1 Figure 2 Figure 3 Figure 4
Loughmiller, D. (Photographer) (2012). Demonstratin of conservation of mass [Print].
Check for Understanding: Allowing students to relate a definitio an experience, such as the demonstration, helps to solidify understanding of concepts.
8. Repeat the activity (steps 4 and 5), but this time cut a hole in the balloon. 9. Ask: • •
Can you explain what has happened in both of these situations? Accept all reasonable answers. What is a chemical reaction? (Chemical reactions occur when two chemicals unite or react to form a compound that is unlike the original substances and cannot be changed back to its original form.) Review this definition as needed.
Science Notebooks: Students draw the demonstration set record the definition of the law of conservation of mass, and then write reflection relating the two.
10. After the class has thoroughly discussed what has occurred, project the following definition for the law for the conservation of mass. • The law of conservation of mass states that the mass of a closed system of substances will remain constant, regardless of the processes acting inside the system. An equivalent statement is ©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
that matter cannot be created nor destroyed, although it may change form.
11. Instruct students to copy down the definition in their science notebooks. 12. Ask students to discuss the definition with a partner and relate the parts of the closed system to the demonstration. For example, the closed system was the water bottle, the antacid tablet, the water, and any gas inside.
13. Facilitate a discussion including the following, and ask for volunteers to share their thoughts regarding the demonstration with the class. • The total mass of reactants in a chemical reaction will equal the total mass of the products. • Gases are produced during some chemical reactions and can be forgotten because they cannot be seen. The mass of the gas needs to be calculated and added to the products when determining the final mass of a reaction. Use a plastic bag or a balloon to collect the gas, and then add this mass to the final reaction products. • Remember, mass is not created or destroyed so when balancing a chemical equation, one must make sure that the number of atoms of each of the reactants on the left side of the equation equals the number of atoms of the products on the right side of the equation. Ex. If you have four atoms of oxygen on the reactant side, make sure that you have four on the product side.
14. Instruct students to write a reflection in their notebooks relating the demonstration to the law of conservation of mass.
EXPLORE/EXPLAIN I – Modeling Equations
Suggested Day 2
1. Divide the class into pairs. Distribute a resealable, plastic bag that has one color gumdrop that will represent a single oxygen atom and one color gumdrop that will represent a single hydrogen atom (see Advance Preparation) to each group. Ask: • Does anyone remember the chemical formula for water? Students should remember H2O from middle school. • Can you make a model of water using these two ‘atoms’? (No, because there are not enough “H” gumdrops.) 2. Explain to students that in reality, elemental hydrogen and elemental oxygen are both diatomic, meaning that hydrogen and oxygen are among seven elements (called diatomic) that only exist in nature in pairs. The complete list is H, N, O, F, Cl, Br, and I. 3. Ask: • What is responsible for the behavior of bonding between ©2012, TESCCC
06/12/13
Materials: • bags of single atom gumdrops (s Advance Preparation, 1 bag per • bags of oxygen molecule gumdro (see Advance Preparation, 1 bag pair) • bags of hydrogen molecule gumdrops (see Advance Preparation, 1 bag per pair) • bags of additional gumdrops (see Advance Preparation, 1 bag per Single hydrogen and oxygen gumdrops page 5 of 12
IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
elements? (Valence electrons. The outermost shell of an atom is called its valence shell. It is the decisive shell during bonding. Only the electrons of this outermost shell are involved during bonding; electrons are either: given away from the outermost shell, accepted into the outermost shell, or shared with the electrons in the outermost shell of another element. This explains the reactivity of elements which may result in chemical reactions.) 4. Collect the first resealable, plastic bag, and distribute two new bags, one that has two gumdrops joined together with toothpicks representing oxygen molecules and the other that has two gumdrops joined together representing hydrogen molecules (see Advance Preparation). Ask: • Can you make a model of a water molecule with these new bags? Accept all answers. 5. Explain that even though there are enough atoms, the answer is still “no” because we would end up with one single oxygen atom, and because hydrogen and oxygen have to be bonded to another element or paired with other atoms, the bonding will not work. Ask: • What number or combination of gumdrops would you need so that hydrogen and oxygen could be paired and end up making one or more water molecules with no atoms left over? This question is intended to get students to reflect. Do not give the answer at this time. 6. Make as many gumdrops available to students as they may need to experiment with the ratios. After a few minutes, ask the question (above) again. Students should arrive at the answer that two pairs of hydrogen gumdrops and one pair of oxygen gumdrops will start off joined, yet still allow them to end up with two water molecules with no atoms left over.
Paired hydrogen and oxygen gumdrops
Loughmiller, D. (Photographer) (2012). Gumdrop ato [Print].
Instructional Notes: There are several websites available do an excellent job of describing the process of balancing equations. Consider mixing such activities in as practice and homework throughout th week.
Writing equations and using subscrip covered in greater depth in chemistry
Misconceptions: • Students may think that a chemic change changes the atoms themselves.
Science Notebooks: Students copy sample equations and label the components in their noteboo
7. Repeat the process with chemical equations you have modeled on the board or projected. Working with a concrete model first should demonstrate to students how electrons work within bonding. 8. Write the following on the board: First Equation H + O H2 O 9. Review with students that the 2 in H2O is called a subscript and represents a pair of hydrogen atoms. The elements or compounds on the left side of the equation are reactants, the ones on the right side are products, and the arrow is a yields sign. Ask for a volunteer to come to the board and count the number of hydrogen atoms on the left side of the equation and then the numbers on the right side of the equation. Repeat ©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
the same task for oxygen. Ask: 1. What is wrong with the equation? (Hydrogen and oxygen elements are not ‘traveling’ in pairs, and there are more hydrogen atoms on the right side of the equation than on the left.) 10. Write the following on the board: Second Equation H2 + O2 H2O 11. Ask:
2. Is this equation correct? (No) Their answer should still be “no” because the number of atoms on both sides still don’t match. 12. Write the correctly balanced equation. Third Equation 2H2 + O2 2H2O 13. Review the fact that we have now added a number, called a coefficient, in front of the letters, which are a chemical symbols. The coefficient carries forward to all elements in the compound. 2H2 + O2
2H2O
2 X H2 = 4H O2 = 2O
2 X H2 = 4H 2 X O = 2O
14. Instruct students to copy down the correct formula and then label the above equation with the terms: subscript, coefficient, reactants, products, and yield. Monitor for correct labeling. 15. Explain that the first equation represents their first bag, the second equation represents the second pair of bags, and the third equation matches their prediction that two pair of hydrogen gumdrops and one pair of oxygen gumdrops would be needed to have an even number of pairs to start with in order to create water molecules (with no “left over” atoms). 16. Point out to students that the last model illustrates the law of conservation of mass. 17. Say:
3. This law states: in a chemical reaction, the mass of the products (what you start with) is equal to the mass of the reactants (what you end with). ©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
18. Facilitate a discussion in which students reflect on the following questions. Ask: 4. How would the law of conservation of mass apply to chemical reactions? (The law of conservation of mass is often applied to basic chemical reactions to explain what happens on an atomic level during a reactionthat every atom present at the start of the reaction is still present at the end of the reaction.) 5. In what ways is it helpful to know that the mass before and after a reaction is constant? Accept appropriate answers. 6. What information can a chemical equation relay? Accept appropriate answers.
ELABORATE I – Balancing Equations Practice
©2012, TESCCC
Suggested Day 2 (continued)
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures 1. Ask students to review their definition of the law of conservation of mass in their notebooks.
2. Ask for student volunteers to restate the law in their own words. Answers will vary, but correct any misconceptions.
3. Inform students that today they will be practicing the balancing of equations, just as they did the previous day with the gumdrops.
4. Distribute the Handout: Balancing Equations Practice Sheet to each student.
5. Model an example problem or two on the board for students, balancing the equation.
6. Ask students to complete the next equation and then stop. 7. Ask for a volunteer to come to the board and show how they completed the problem. Work with the student to clarify, and assist them in completing the problem, if needed.
8. Inform students they will have most of the class to complete the handout, but that the class will discuss the problems during the last 15 minutes of the period.
9. Monitor and assist students as they complete the rest of the problems.
Notes for Teacher Materials: • glue or tape (per group)
Attachments: • Handout: Balancing Equations Practice Sheet (1 per student) • Teacher Resource: Balancing Equations Practice Sheet KEY
Instructional Notes: Exercise sensitivity in calling student work problems on the board. Try to choose volunteers or choose specific students who have correctly answere the problems. One way to do this eas is to walk by students’ desks and ma check mark by correctly completed examples that students will later shar with the class.
Science Notebooks: Students affix correctly completed handouts in their notebooks to use fo later reference.
10. When the majority of students are finished, ask for volunteers to come to the board to show and explain how they worked each problem. Clarify misconceptions, and instruct students to revise their handouts as necessary.
11. Instruct students to affix the handouts in their notebooks. EXPLORE/EXPLAIN II – Law of Conservation of Mass Investigation 1. Inform students they will be completing two activities to demonstrate the law of conservation of mass.
2. Divide the class into groups. 3. Distribute a copy of the Handout: Law of Conservation of Mass. Instruct students to read through the first activity carefully. Address safety precautions and lab cleanup procedures. Answer any questions students may have about the first activity.
4. Monitor and assist students as they complete Activity 1. ©2012, TESCCC
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Suggested Days 3 and 4
Materials: • resealable plastic bag (gallon-siz per group) • cup (small, plastic, 2 per group)
• • •
vinegar (acetic acid, 1 small container per group) baking soda (sodium bicarbonate small container per group) triple beam balance (1 per group page 9 of 12
IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures 5. When groups have completed the first activity, facilitate a discussion in which students share their results and reflect on how the investigation relates to the law of conservation of mass.
6. Instruct students to read through the second activity carefully. Address the steps the groups will use to plan their investigation. Answer any questions they may have regarding the preparation of the plan.
7. Remind students they must have their plan approved before any testing may occur.
8. Monitor and assist groups in planning their investigations and then in completing the investigations.
9. Facilitate a discussion in which each group shares a summary of their procedure and their results. Include the following questions in the discussion: Say/Ask: • The law of conservation of mass applies only to a closed system. • What is a closed system? (A system in which energy or matter is not gained or lost by the system is considered a closed system.) • Why does the law of conservation of mass apply only to closed systems? (Theoretically, nothing in nature is totally isolated and energy or matter may be transferred in or out of a system in many forms, including chemical, heat, and light. Therefore, the law of conservation of mass applies only to closed systems. In this case, nothing is created nor destroyed.)
Notes for Teacher • seltzer tablets (amount will vary p • • • •
group based on student design) flask (1 per group) flask stopper (1 per group) water (per group) safety goggles (1 per student)
Attachments: • Handout: Law of Conservation Mass • Teacher Resource: Law of Conservation of Mass KEY
Safety Notes: Safety goggles must be worn for this activity.
ELABORATE II – Baggie Fun 1. Inform the class that today they will complete an activity and then will be 2. 3.
4.
5.
Suggested Day 4 (continued) Materials: 8. station bags (see Advance sharing their results with the class. Preparation, enough for each gro to have 1 bag, per class per Stati Divide the class into ten groups. You will need to gather materials for two 2-5): sets of the five stations (see Advance Preparation). 9. resealable plastic bags Explain to the students that each group will complete only one station. 10. walnuts in shells Students will have 45 minutes to observe the outcome of their specified 11. ice cubes activity and make as many measurements as they can. hammer (1 per Station 1) beakers (large, 1 per Station 2) Instruct the groups to read the instructions on their station card, complete 14. beakers (small, 4; 2 per Station 4 the investigation, record their observations and set up in their notebooks, per Station 5) and then clean up their station. water (warm, per Station 2) paper towels (1 roll, per Station 2) Remind students to wear their safety goggles throughout the activity. 17. Play-Doh® (large amount, per
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures 6. Instruct students to have a representative from their group transfer the group's findings to an appropriate table on the board, so that the whole class can see the outcomes of the other groups.
7. Assign a station to each group. Monitor and assist groups as they complete the activity.
8. After the activity is completed, facilitate a discussion in which each group summarizes their activity and their results.
9. Ask: 7. What did each of the activities have in common? The students should find that mass is conserved in all examples.
10. Encourage each group to respond to the question. Clarify any misconceptions, especially if a group’s data doesn’t correlate with the other groups’ data. Look for errors in student procedures, and discuss how retesting could be done.
Notes for Teacher Station 3)
18. weigh paper (several sheets per group at Station 3)
19. water (tap, per Stations 4; warm
Station 5) 20. Epsom Salts™ (250 g minimum, Station 4) 21. sugar (70 g minimum, per Station 22. wooden craft stick (2, 1 per Statio 4 and 5) 23. triple beam balance (1 per station safety goggles (1 per student) Attachments: • Teacher Resource: Baggie Fun Station Cards (see Advance Preparation, 1 per station)
Safety Notes: Predetermine if anyone in your class nut allergies. Safety goggles must be worn for this activity.
Instructional Notes: While these activities may seem simp they reinforce the law of conservation mass.
The law of conservation of mass, als known as the principle of mass/matte conservation, states that the mass of closed system (in the sense of a completely isolated system) will rema constant over time.
This principle is equivalent to the conservation of energy, in the sense when energy or mass is enclosed in system and none is allowed in or out quantity cannot otherwise change. Th mass of an isolated system cannot b changed as a result of processes act inside the system.
The law implies that mass cannot be created or destroyed, although it may ©2012, TESCCC
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IPC HS/Science Unit: 04 Lesson: 01
Instructional Procedures
Notes for Teacher
rearranged in space and changed int different types of particles; and for an chemical process in a closed system mass of the reactants must equal the mass of the products. Science Notebooks: Students draw set ups, record observations, and answer questions their science notebooks.
EVALUATE – Performance Indicator - Balanced Equations Performance Indicator • Select a balanced equation from a laboratory investigation. Use the balanced equation to explain and demonstrate the law of conservation of mass. Present information in a diagram, and explain, in writing, how the balanced equation represents a chemical change. Demonstrate that the number and kind of atoms are the same in the reactants and products. (I.2E; I.7C) 1C, 1E; 5G 1. Refer to the Teacher Resource: Evaluate Instructions PI for information on administering the performance assessment.
Suggested Day 5 Attachments: • Handout: Balancing Equations Practice Sheet (previously distributed) • Teacher Resource: Balancing Equations Practice Sheet KEY • Teacher Resource: Evaluate Instructions PI (1 for projection)
Science Notebooks: Students refer to their notes in order complete the assessment. The assessment may be completed in the science notebooks.
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