Chemical Reactions
Conservation of Matter
Chemical Reactions
Conservation of Matter
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.
Charles A. Dana Center at The University of Texas at Austin
Teacher Pages–1
Chemical Reactions:
Conservation of Matter
4.
Middle School Physical Science Formative Assessments
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
3.
6 oxygen
6 hydrogen
3 sodium
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?
2H2 + O2 " 2H2O
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
Charles A. Dana Center at The University of Texas at Austin
Middle School Physical Science Formative Assessments
Chemical Reactions:
Conservation of Matter
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
HC2H3O2 + NaHCO3 " NaC2H3O2 + H2O + CO2
Reactants: Count the number of atoms of each element in the baking soda (NaHCO3)
and in the vinegar (HC2H3O2). Write the totals on the chart below in the Reactants
column.
Products: Count the number of atoms of each element in the sodium acetate
(NaC2H3O2), in the water (H2O), and in the carbon dioxide (CO2). Write the totals on the
chart in the Products column.
Number of atoms of each element
Atoms
Products
carbon
3
3
hydrogen
5
5
oxygen
5
5
sodium
1
1
14
14
Total
2.
Reactants
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.
Charles A. Dana Center at The University of Texas at Austin
Teacher Pages–3
Chemical Reactions:
Conservation of Matter
3.
Middle School Physical Science Formative Assessments
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
4.
Vinegar tiles drawing
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
Charles A. Dana Center at The University of Texas at Austin
Middle School Physical Science Formative Assessments
Sodium acetate tiles
6.
Water tiles
Chemical Reactions:
Conservation of Matter
Carbon dioxide tiles
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
Conservation of Matter?
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.
Charles A. Dana Center at The University of Texas at Austin
Teacher Pages–5
Chemical Reactions:
Conservation of Matter
9.
Middle School Physical Science Formative Assessments
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
Charles A. Dana Center at The University of Texas at Austin
Middle School Physical Science Formative Assessments
Chemical Reactions:
Conservation of Matter
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.
Charles A. Dana Center at The University of Texas at Austin
Teacher Pages–7
Chemical Reactions:
Conservation of Matter
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
Charles A. Dana Center at The University of Texas at Austin
Blackline Masters
Chemical Reactions
Conservation of Matter
Charles A. Dana Center at The University of Texas at Austin
Blackline Masters–1
Chemical Reactions:
Conservation of Matter
2–Blackline Masters
Middle School Physical Science Formative Assessments
Charles A. Dana Center at The University of Texas at Austin
Middle School Physical Science Formative Assessments
Chemical Reactions:
Conservation of Matter
Atom Tile Stickers
Charles A. Dana Center at The University of Texas at Austin
Blackline Masters–3
Chemical Reactions:
Conservation of Matter
Middle School Physical Science Formative Assessments
Station Information Sheet
for Chemical Reactions: Conservation of Matter
4–Blackline Masters
Charles A. Dana Center at The University of Texas at Austin
Chemical Reactions
Conservation of Matter
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?
2H2 + O2 ! 2H2O
Charles A. Dana Center at The University of Texas at Austin
Student Pages–1
Chemical Reactions:
Conservation of Matter
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
HC2H3O2 + NaHCO3 ! NaC2H3O2 + H2O + CO2
Reactants: Count the number of atoms of each element in the baking soda
(NaHCO3) and in the vinegar (HC2H3O2). Write the totals on the chart below in
the reactant column.
Products: Count the number of atoms of each element in the sodium acetate
(NaC2H3O2), in the water (H2O) and in the carbon dioxide (CO2). 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
Charles A. Dana Center at The University of Texas at Austin
Middle School Physical Science Formative Assessments
Chemical Reactions:
Conservation of Matter
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
4.
Vinegar tiles drawing
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
Charles A. Dana Center at The University of Texas at Austin
Student Pages–3
Chemical Reactions:
Conservation of Matter
5.
Middle School Physical Science Formative Assessments
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
6.
Water tiles
Carbon dioxide tiles
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 Conservation of Matter?
Student Pages–4
Charles A. Dana Center at The University of Texas at Austin
Middle School Physical Science Formative Assessments
Chemical Reactions:
Conservation of Matter
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)?
Charles A. Dana Center at The University of Texas at Austin
Student Pages–5
Chemical Reactions:
Conservation of Matter
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
Charles A. Dana Center at The University of Texas at Austin
Middle School Physical Science Formative Assessments
Chemical Reactions:
Conservation of Matter
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.
Charles A. Dana Center at The University of Texas at Austin
Student Pages–7
Chemical Reactions:
Conservation of Matter
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
Charles A. Dana Center at The University of Texas at Austin
Middle School Physical Science Formative Assessments
Chemical Reactions:
Conservation of Matter
Glossary for Chemical Reactions: Conservation of Matter
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.
Conservation of Matter
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.
Charles A. Dana Center at The University of Texas at Austin
Student Pages–9
Chemical Reactions:
Conservation of Matter
Student Pages–10
Middle School Physical Science Formative Assessments
Charles A. Dana Center at The University of Texas at Austin