# Conservation of Mass

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26 Νοε 2013 (πριν από 4 χρόνια και 5 μήνες)

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IPC

HS/Science

Unit: 04

Lesson: 01

Suggested Duration: 5

days

Conservation of Mass

2012
, TESCCC

06/12/13

page
1

of
9

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.

valence
electrons and that the behavior of valence electrons
is

responsible f
or chemical changes.

Students will plan and
implement an investigation to demonstrate their understanding of the law of conservation of mass.

TEKS
:

I.
7

Science concepts.
The student knows that changes in matter affect everyday life.

The student is
expected to:

I.
7B

Recognize that
chemical changes can occur when substances react to form different substances

and that these

interactions are largely determined by the valence electrons.

I.
7C

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
P
rocess

TEKS:

I.
2

Scientific processes. The student uses scientific methods during laboratory and field investigations. The student is
expected
to:

I.
2E

C
ommunicate valid conclusions
.

G
ETTING
R
I
NSTRUCTION

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 cha
nge. 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 i
s
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 潦⁣潮s敲e慴i潮⁯ ⁭慳s

yi敬搠dign

s畢scri灴

c潥ffici敮t

r敡c瑡t瑳

val敮c攠敬散瑲潮s

c桥mic慬⁥ 畡瑩on

Materials
:

Refer to Notes for Teacher section for materials.

Attachments:

Handout:
Balancing Equations Practice Sheet

(1 per stud
ent)

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

(
1 per station)

IPC

HS/Science

Unit: 04 Lesson: 01

, TESCCC

06/12/13

page
2

of
9

Teacher Resource:
Evaluate Instructions PI

(1 for projection)

1.

Prior to Day 1, c
reate 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
gumdrop
s joined together with
to
othpicks representing oxygen
molecul
es
,
and
the
third set will have
two
gumdrop
s 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 t
wo 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 kind
s

of atoms are the same in the reactants and products. In addition, they recognize valence electrons
,

and
how
the
behavior of val
ence electrons is

responsible for chemical changes.
In this lesson
,

students will
also
be learning
about synthesis, decomposition, combustion, double replacement, and single replacement reactions.

G
ETTING
R
I
NSTRUCTION
S
UPPLEMENTAL
P
LANNING
D
OCUMENT

Instructors are encouraged to supplement and substitute resources, materials, and activities to differentiate instruction to
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 pa
ge.
All originally authored lessons can be saved in the “My CS
COPE” Tab within the “My Content” area.

I
NSTRUCTIONAL
P
ROCEDURES

Instructional Procedures

Notes for Teacher

ENGAGE

Conservation of Mass Demonstration

NOTE:
1 Day = 50 minutes

Suggested
Day 1

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)
.

2.

to
draw the
set
up of the demonstration in their notebooks.

3.

Break
up an antacid tablet
,

and place the pieces inside the balloon
.

S
tretch
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
.

4.

Place the bottle with water, antacid, and balloon on top
of the triple beam
balance
,

and
have a student volunteer mass the
s
ystem 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.

What do you think will happen when you let the pieces of antacid
tablets fall i
n
to the water?

Will the system with the bottle weigh
more or less?

Accept all answers at this time.

The main question for
the cl
ass to ponder is whether the bottle apparatus will weigh more,
less, or the same while the tablet dissolves and after the tablet

M
aterials
:

triple beam balance

(1 per teacher)

balloon
s

(1
or more per class
)

water

bottle (clear, filled with tap
water, 1 per teacher
)

effervescent antacid tablet

(1 per
class)

Instructional Notes:

Figure 1

IPC

HS/Science

Unit: 04 Lesson: 01

, TESCCC

06/12/13

page
3

of
9

Instructional Procedures

Notes for Teacher

dissolves.

7.

Manipulate the balloon so that the pieces of antacid fall in without
dislodging the balloon.

At all points during t
he 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
.
)

8.

Repeat the activity (steps 4 and 5), but this time cut a hole in the balloon.

9.

:

Can you e
xplain what
has happe
ned in both of these situations?

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 o
riginal form.
)

Review
this definition as needed.

10.

After the class has thoroughly discussed what has occurred,
project the
following definition for

the
law for the conservation of mass.

The
l
aw of
c
onservation of
m
ass 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
that matter cannot be created nor destroyed, although it may
change form.

11.

Instruct students to copy down the definition in their sc
ience notebooks.

12.

Ask students to discuss the definition with a partner and relate the parts of
the clos
ed 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
,

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
,

ss 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 pr
oducts on t
he right side of
the equation.
Ex. If you have
four
atoms of
o
xygen 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 con
servation of mass.

Figure 2

Figure 3

Figure 4

Loughmil
l
er, D.
(Photographer)
(2012).
Demonstrating law
of conservation of mass

[Print].

Check for Understanding:

Allowing students to relate a definition to
an experience, such as the
demonstration, helps to solidify
understanding of concepts.

Science Notebooks:

Students draw the demonstration set up,
record the definition of the law of
conservation of mass
,

and then write a
reflection relating the two.

IPC

HS/Science

Unit: 04 Lesson: 01

, TESCCC

06/12/13

page
4

of
9

Instructional Procedures

Notes for Teacher

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

Preparation)

to each group.

Does anyone

remember the chemical formula for water?

S
tudent
s
should remember
H
2
O 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, C
l
, Br, and I.

3.

What is
responsible for
the behavior of bond
ing between
elements
?

(
Valence electrons.
The outermost shell of an atom is
called its
v
alence 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 sh
ell,
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
d
istribute
two

new
bag
s, one
that has two
gumdrop
s joined together with
to
othpicks representing oxygen
molecules

and the other that has two
gumdrop
s joined together
representing hydrogen
molecules
.

Can you make a model of a water molecule
with these new bags
?

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 w
ill not

work.

What number or combination of
gumdrops

would you need so
that hydrogen and oxygen
could be paired

and end up making
one or mor
e water molecules with no atoms left over?

This
question is
intended
to get students to
reflect
. Do
at this time.

6.

Make as many
gumdrop
s available
to

students
as they
m
ay

need to
experiment with the ratios.
After a few minutes
,

again.
Students should a
rrive at
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.

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:

Materials:

bags
of single atom gumdrops
(see

Preparation
, 1 bag per pair
)

bags of oxygen
molecule
gumdrops
(see Advance Preparation, 1 bag per
pair)

bags of hydrogen
molecule
Preparation, 1 bag per pair)

bags of
Advance Preparation, 1 bag per pair)

Single
hydrogen and oxygen
gumdrops

Paired
hydrogen and oxygen
gumdrops

Loughmiller, D. (Photographer) (2012).
Gumdrop atoms

[Print].

Instructional Note
s
:

There are several

websites
available that
do an excellent job of describing the
process of ba
lancing equations.
Consider m
ix
ing

such
activities in as
practice and homework

throughout this
week
.

Writing equations and
using

subscripts is
covered in
greater depth in
chemistry.

Misconception
s
:

IPC

HS/Science

Unit: 04 Lesson: 01

, TESCCC

06/12/13

page
5

of
9

Instructional Procedures

Notes for Teacher

First Equation

H + O

H
2
O

9.

Review

with students
that the 2 in H
2
O 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
h
ydrogen atoms on the left side of the equation and then the
numbers on t
he right side of the equation.
o
xygen.

What is wrong with the equation?

(
Hydrogen and ox
ygen 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

H
2

+ O
2

H
2
O

11.

Is this equation correct?

(
N
o
)

still be “
no
” because the number of atoms on both
sides still don’t match.

12.

Write
the
correct
ly
balanced

equation.

Third Equation

2H
2

+ O
2

2H
2
O

13.

Review the fact that we have now added a number
,

called a
coefficient
,

in
front of the letters
, which are
a chemical symbol
s
.

The coefficient

carries
forward to all elements in the compound
.

2H
2

+ O
2

2H
2
O

2 X H
2

= 4H

2 X H
2

= 4H

O
2

= 2O

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 t
he 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
in order to create
water molecules
(with no

left over
” atoms).

16.

Point out

to students
that
the last model

illustrates

the la
w of conservation
of mass
.

17.

Say:

This law

states
:

in a chemical reaction, the mass of the products

Students may think that
a
chemical
change changes the atoms
themselves.

Science Notebooks:

Students copy sample equations and
label the components

in their notebooks
.

IPC

HS/Science

Unit: 04 Lesson: 01

, TESCCC

06/12/13

page
6

of
9

Instructional Procedures

Notes for Teacher

is equal to
the mass of the reactants (what
you end with).

18.

Facilitate a discussion in which students reflect on the following
questions.

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 reaction

that every atom present at the

start of the reaction is still
present at the end of the reaction.
)

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?

Accept
appropriate an
swers.

ELABORATE I

Balancing Equations Practice

Suggested
Day 2

(continued)

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.

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.

complete

the next
equation

and then stop.

7.

come to the board and show

how they completed the
problem
.
Wo
rk 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 c
omplete the rest of the problems.

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 hando
uts in their notebooks.

Materials:

glue or tape (per group)

Attachments:

Handout:
Balancing Equations
Practice Sheet

(1 per student)

Teacher Resource:
Balancing
Equations Practice Sheet

KEY

Instructional Note
s
:

Exercise sensitivity in calling students
to
work problems on the board.
Try to
choose volunteers or choose specific
students who have co
the problems.
One way to do this
easily
is to walk by students’ desks and make a
check mark by correctl
y
completed

examples that students will later share
with the class.

Science Notebooks:

Students affix correctly completed
handouts in their notebooks to use for
later reference.

EXPLORE
/EXPLAIN

II

Law of Conservation of
Mass

Investigation

Suggested
Day
s

3

and 4

1.

Inform students they will be completing
two activities

to
demonstrate the
law of conservation of mass
.

2.

Divide
the class
into groups.

Materials:

res
ealable plastic

bag

(gallon
-
size
, 1
IPC

HS/Science

Unit: 04 Lesson: 01

, TESCCC

06/12/13

page
7

of
9

Instructional Procedures

Notes for Teacher

3.

Distribute
a copy of the
Handout:
Law of Conservation of
Mass
.

Instruct
first
activity carefully.

precautions and lab cleanup procedures.
students

may have

first
activity.

4.

Monitor and assist students as they complete Activity 1.

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.

steps the groups will use to plan t
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
completi
ng 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:

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.
)

per group
)

cup

(small
,

plastic, 2 per group)

vinegar (acetic acid,
1 small
container
per group)

baking soda (sodium bicarbonate,
1
small container
per group)

triple beam balance

(1 per group)

seltzer tablets (amount will vary
per
group
based on student design)

(1 per group)

water (per group)

safety goggles

(1 per student)

Attachments:

Handout:
Law of Conservation of
Mass

Teacher Resource:

Law of
Conservation of
Mass

KEY

Safety
N
ote
s
:

Safety g
oggles must be worn for this
activity.

ELABORATE

I
I

Baggie Fun

Suggested Day 4

(continued)

1.

Inform the class that today they will complete an activity and then will be
sharing their results with
the class.

2.

Divide the
class
into
ten

groups.
You will need to gather materials for
two

sets of the
five

3.

Explain to the students that e
ach group will

complete only on
e station.
Students will have 4

5 minutes
to observe
the outcome of the
ir

specified
activity and make as many measuremen
ts as they can.

4.

Instruct the groups to read the instructions on their station
card, complete
the investigation,
record their observations and set up in their notebooks,
and then clean up t
heir station.

5.

Remind students to wear their safety goggles throughout the activity.

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.

Materials:

Preparation, enough for each group
to have 1 bag, per class

per Stations
2
-
5
):

resealable plastic bags

walnuts

in shells

ice cubes

hammer

(1 per Station 1)

beakers

(
large,
1 per Station 2)

b
eakers (small, 4; 2 per Station 4; 2
per Station 5)

water

(warm, per Station 2)

paper towels (1 roll, per Station 2)

Play
-
D
oh®

(large amount, per
Station 3)

weigh paper (several sheets per
group at Station 3)

water (tap, per Stations 4
; warm per
IPC

HS/Science

Unit: 04 Lesson: 01

, TESCCC

06/12/13

page
8

of
9

Instructional Procedures

Notes for Teacher

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 act
ivity and their results.

9.

W
hat
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.

Station 5
)

Epsom Salts™

(250 g minimum, per
Station 4)

s
ugar (
70 g minimum, per Station 5)

wooden craft stick (
2, 1 per Stations
4 and 5
)

triple beam balance

(1 per station)

safety
g
oggles

(1 per student)

Attachments:

Teacher Resource
:
Baggie Fun
Station Cards
(
Preparation,
1 per station)

Safety
N
ote
s
:

Predetermine if anyone in your class has
nut allergies.
Safety g
oggles

must be
worn for this activity.

Instructional
Note
s
:

While these activities
may
seem simple,
they reinforce the
l
aw of
c
onservation of
m
ass.

The
law of conservation of mass
, also
known as the
principle of mass/matter
conservation
, states that the
mass

of a
closed system

(in the sense of a
completely isolated system) will remain
constant over time.

This
principle

is equivalent to the
conservation of energy, in the sense
that
when energy or mass is enclosed in a
system and none is allowed in or out
,

its
quantity cannot otherwise change. The
mass of an isolated system cannot be
changed as a result of processes acting

inside the system.

The law implies that mass cannot be
created or destroyed, although it may be
rearranged in space and changed into
differe
nt types of particles; and
for any
chemical process in a closed system, the
mass of the reactants must equal the
mass of the products.

Science Notebooks:

Students draw set ups, record
observations
,

their science notebooks.

IPC

HS/Science

Unit: 04 Lesson: 01

, TESCCC

06/12/13

page
9

of
9

Instructional Procedures

Notes for Teacher

EVALUATE

Performance Indicator
-

Balanced Equations

Suggested Day 5

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 cha
nge. 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

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 to
complete the assessment. The
assessment may be completed in their
science notebooks.