24
3
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se
m i nu t e
ss
i
ACTIVITY OVERVIEW
LA
O
RY
5 0-
on
40
to
s
Diluting the Problem
BO RA
T
Students explore dilution as a disposal method for copper-containing solutions produced during circuit-board manufacturing. They construct a serial dilution of
100,000 ppm used copper chloride solution and add ammonia to demonstrate that
chemical tests can reveal concentrations lower than those visible to the human eye.
They then use the serial dilution for comparison in determining the concentration of
the copper chloride waste from Activity 23, “Producing Circuit Boards.”
KEY CONCEPTS AND PROCESS SKILLS
(with correlation to NSE 5–8 Content Standards)
1.
The amount of a contaminant in air or water is often expressed in parts per million or even parts per billion.
2.
Toxic waste is harmful to living organisms and must be disposed of according to
strict guidelines. (Perspectives: 4)
3.
Students will use math in all aspects of scientific inquiry. (Inquiry: 1)
KEY VOCABULARY
concentration
control
dilution
indicator
parts per million (ppm)
serial dilution
B-137
Activity 24 • Diluting the Problem
MATERIALS AND ADVANCE PREPARATION
For the teacher
*
*
1
Science Skills Transparency 2, “Use of a Dropper Bottle”
1
Literacy Transparency 3, “Reading Scientific Procedures”
1
Transparency 24.1, “Diluting and Testing Copper Chloride”
(photocopy at 108%)
1
Transparency 24.2, “Treating Waste Concept Map”
1
transparency of Student Sheet 24.1, “Determining Concentration”
1
transparency of Student Sheet 24.2, “Treating Waste”
1
overhead projector
2
plastic cups
1
bottle of red food coloring
*
supply of water
*
1
pair of disposable latex gloves
*
1
pair of safety goggles
*
1
funnel
*
1
container for liquid waste
For each group of four students
1
labeled 30-mL dropper bottle of each of the following:
100,000 ppm copper chloride solution
water
5% ammonia solution
used copper chloride solution from Activity 23, “Producing
Circuit Boards”
1
cup of water
For each pair of students
*
1
SEPUP tray
1
dropper
1
stir stick
1
copy of Transparency 24.1, “Diluting and Testing Copper Chloride”
(photocopy at 108%)
1
sheet of white paper
*
paper towels
For each student
*
1
pair of safety goggles
1
Student Sheet 24.1, “Determining Concentration”
1
Student Sheet 24.2, “Treating Waste”
1
Student Sheet 24.3, “Diluting Used Copper Chloride Solution to
1 ppm Copper” (optional)
*Not supplied in kit
B-138
Diluting the Problem • Activity 24
Masters for Scoring Guides are in Teacher Resources III: Assessment. Masters for Science Skills sheets and literacy transparencies are in Teacher Resources II: Diverse
Learners.
When making a transparency and photocopies of Transparency 24.1, photocopy at
108% so that it fits directly under the wells of the SEPUP tray. If you would like students
to place the copy under their SEPUP tray as they work, make enough photocopies for
each pair of students.
Pour equal amounts of used copper chloride solution from Activity 23, “Producing
Circuit Boards,” into eight 30-mL dropper bottles labeled “Used Copper Chloride
Solution.”
Add 10 drops of red food coloring to a plastic cup that is half filled with water. Fill a
second cup one quarter full of water.
Set out a waste container labeled to collect copper chloride waste solutions from this
activity.
Students will use Student Sheet 24.2, “Treating Waste” again in Activities 26, 27, and
28. Decide on a place in the classroom where students can access the sheet easily or
where they can keep them for use during these upcoming activities.
SAFETY
Have students wear protective eyewear during the activity. Solutions used in this activity, such as ammonia and the copper chloride waste solution, are toxic and corrosive.
Avoid contact with skin and eyes. Wash with water for 2–3 minutes any area that
comes in contact with the solution. If contact with an eye occurs, rinse eye for 15–30
minutes, and consult a doctor.
Disposal
It is important that you dispose of the liquid waste generated in this activity and others in the unit in accordance with your local regulations. It contains copper, a regulated heavy metal, in concentrations of 1–100,000 parts per million (ppm). For more
information, see the Safety section in Activity 23, “Producing Circuit Boards.”
B-139
Activity 24 • Diluting the Problem
TEACHING SUMMARY
Getting Started
1.
Introduce the copper chloride waste problem.
2.
Discuss what is meant when concentration is expressed in parts-per-million.
Doing the Activity
3.
Students perform a serial dilution of a copper chloride solution that has a known
concentration.
4.
Students determine the concentration of copper in the used copper chloride solution.
Follow-Up
5.
The class calculates copper concentration in the used copper chloride solution in
parts per million and as a fraction.
6.
The class discusses dilution as a treatment for the used copper chloride.if this wor
BACKGROUND INFORMATION
Copper and Health
Small amounts of copper are essential to the lives of many kinds of organisms. In
green plants copper is part of a molecule that plays a role in photosynthesis. In
humans copper acts as a coenzyme for some metabolic processes. In larger amounts,
however, copper is quite toxic. Although the exact amount of copper that can kill a
human is not known, it is known that a level of 5–8 mg/1 kg of body weight can cause
illness after ingestion. Levels of 40 mg/1 kg could possibly cause death.
B-140
Diluting the Problem • Activity 24
TEACHING SUGGESTIONS
GETTING STARTED
1.
Explain the copper chloride waste problem.
Show students the copper chloride waste solution
produced in Activity 23, “Producing Circuit
Boards.” Explain that this is similar to the waste
from actual circuit-board production. Remind them
that the main components of the solution are water
and copper-containing compounds formed when
the copper-etching solution chemically reacted
with the copper metal. Once the circuit board is
etched, the copper chloride solution is left over, and
manufacturers must decide how to handle the
resulting waste. Ask students, What should we do
with our used copper chloride solution? Encourage
the class to brainstorm a list of options. Students’
answers will likely include pouring the solution
down the drain and delivering the solution to a
waste-collection site. Consider looking up with the
class local limits for pouring copper-containing
solutions down the drain. Explain that it might
seem easiest to pour it down a sewer. But the harm
to animals and humans when too much copper is
released into the water systems is a health hazard.
Like other toxic substances, the disposal of copper is
regulated by laws that set limits on what wastes can
be released into the environment. Tell students that
while living things need copper in small amounts,
in larger amounts copper can be toxic and is a problem too big to ignore. For more information of the
effects of copper on health see the Background
Information.
In most places, the concentration of copper in
wastewater cannot exceed 1–10 parts per million
(ppm). Parts per million is a way to measure the
concentration of one component compared to the
amount of the whole mixture. This concept will be
developed in Teaching Step 2 and further explored
in Unit C, “Water,” of Issues and Physical Science.
Explain to students that in this activity they will
determine the concentration of copper chloride in
the used copper chloride solution in parts per million (ppm). This will help them determine how
much water it would take to dispose of the waste
according to legal regulations. Point out that many
units can communicate concentration, but partsper-million is often used when talking about substances for which a very small amount in a large
volume is significant because the solution can still
be toxic.
2.
Discuss what is meant when concentration
is expressed in parts per million.
Talk with the class about ways in which concentrations are described. Students may be familiar with
concentrations expressed in percentages, such as
the 5% alcohol solution used in this activity. You
might hold up a container of hydrogen peroxide or
rubbing alcohol that shows the percent composition. Students may not be familiar with the concept
of parts per million (ppm). Tell them that parts per
million is a measurement that describes the
amount, or concentration, of one substance in a
mixture, as in one part copper in a solution of a million parts. In this activity student will determine the
concentration of copper in a rinse-water solution.
For students to effectively perform the serial dilution in the first part of this activity, they will need to
understand the measurement of parts per million.
Parts per million is the key concentration in this and
subsequent activities since it describes substances
that while very low in concentration, remain toxic
to the health of humans and animals.
To demonstrate parts per million show students a
plastic cup containing red food coloring and water.
Explain how you prepared this solution. Then pour
half the solution into a second cup. Ask, What is the
concentration of the solution in the second cup—
more, less, or the same as the first cup? The answer is
that it is the same. Next add water to the second
cup, and repeat the question, What is the concentration of the solution in the second cup—more, less, or
the same as the first cup? This time, the answer is
less because when more water was added it lowered
the amount of food coloring in water. This is a more
dilute solution.
Emphasize that adding more water, and making
the amount of red food coloring in the cup dilutes
the solution. The solution in the first cup is more
B-141
Activity 24 • Diluting the Problem
concentrated, while the solution in the second cup
is more dilute. Generally, if a solution is colored—as
with food coloring or tea—the color becomes less
visible as it becomes more dilute. Ask students, How
could you make the solution in the second cup (or the
first cup) more dilute? They may suggest adding
more water, or removing some of the food coloring.
Emphasize that both of these methods decrease the
amount of food coloring per volume of water, or
concentration. Understanding the concept of concentration will help them as they construct a serial
dilution and determine how many parts per million
of copper are in the waste solution from Activity 23,
“Producing Circuit Boards.”
DOING THE ACTIVIT Y
3.
Students perform a serial dilution of a
copper chloride solution that has a known
concentration.
Explain that a serial dilution is a way to approximate concentration of a substance. Let students
know that they will take a substance of known concentration (100,000 ppm) and dilute it. Then they
will compare this to the concentration of the used
copper chloride from Activity 23, “Producing Circuit
Boards,” to determine its concentration.
Instruct students in the proper use of the dropper
bottles as shown on Science Skills Transparency 2,
“Use of a Dropper Bottles.” When SEPUP dropper
bottles are held upside down and vertically, the bottles produce drops of consistent size, allowing for
reproducible measurements. This is especially
important when constructing a serial dilution, a
tool that will assist students in determining concentration. Approximately 14-20 drops from the SEPUP
dropper bottles equals 1 mL.
As a class read the introduction, Challenge, and
review the Procedure. Point out that Cup 8 will contain water only, this is to be used as a control for
comparison purposes. Assure that students understand the importance of cleaning the dropper in
between cups so as not to unnecessarily add additional copper to any of the cups in the serial dilution. You may want to use Transparency 24.1,
B-142
“Diluting and Testing Used Copper Chloride,” in
reviewing the Procedure. Hand out Student Sheet
24.1, “Determining Concentration.” As the students
work on the investigation, circulate around the
classroom. Monitor and assist where needed, but
encourage each pair of students to work as independently as possible.
This activity requires students to read a scientific
procedure. Encourage students to be independent
as they read and complete the procedure. If you o
bserve they need support, model the strategies on
Literacy Transparency 3, “Reading Scientific Procedures”. Learning and practicing these skills will
help students become more independent in laboratory activities and become stronger readers.
4.
Students estimate the concentration of
copper in the used copper chloride
solution.
In Part B of the Procedure students use the serial
dilution they created in Part A with the solution of
known concentration to estimate the unknown concentration of copper in the used copper chloride
solution, from Activity 23, “Producing Circuit
Boards.”
Students will add ammonia to detect the presence
of copper ions at a concentration greater than 100
ppm. When ammonia is mixed with the coppercontaining solutions, the ammonia initially forms a
precipitate of milky-green copper hydroxide. As
more ammonia is added, the precipitate dissolves
and the solution turns blue, indicating the presence
of the copper-ammonia ion. Seeing if this complex
chemical reaction occurs is a more reliable test for
detecting unsafe levels of copper than judging solution color alone.
Constructing the serial dilution while using the
ammonia indictor allows students to determine the
concentration of the copper chloride waste. Typically students’ results after the serial dilution lead
them to estimate the concentration of copper
chloride in the waste solution to be approximately
50,000 ppm through 100,000 ppm.
Diluting the Problem • Activity 24
The equations for these reactions are as follows:
Cu2+
+
2OH-
Þ
Cu(OH)2
(milky green precipitate)
Cu(OH)2 + 4NH3
Þ
[Cu(NH3)4]2+ + 2OH(blue ion)
n Teacher’s Note: If in Procedure Step 10 adding 5
drops of ammonia to Cup 1 produces only a milkygreen precipitate, tell students to increase the number of drops one at a time until a blue color is
obtained. If it takes more than 10 drops to produce
the blue color, you should replace the ammonia
with fresh ammonia. Sample student results are
shown on the next page. Students will calculate the
concentration for each of the cups during Teaching
Step 4.
After students have completed the lab, they should
pour the waste solutions into the waste container
you have provided and use their droppers to transfer any remaining liquid into the waste container as
well. To ensure that no copper-containing wastes
are washed down the drain, give students paper
towels to wipe off remaining copper-containing
solutions from trays and equipment before washing
all equipment.
FOLLOW-UP
5.
The class calculates the copper
concentration in the used copper chloride
solutions in parts per million and as a
fraction.
Ask students to share the observations they
recorded in their tables. Display Transparency 24.1,
“Diluting and Testing Used Copper Chloride,” and
point out the concentration of the solution in Cup 1
is 100,000 ppm as shown on the bottle. Next
explain that 100,000 ppm is equivalent to the fraction 100,000/1,000,000. Write this value in the column titled “As a fraction.” Show how this fraction
can be reduced, or simplified, to 1/10 by crossing
out the same number of zeroes in the denominator
and numerator. Write this value in the column
titled “As a simplified fraction” on Student Sheet
24.1, “Determining Concentration.” Tell students
that 1/10 is the same as one part in 10.
Remind students that each cup was diluted with
nine drops, or parts, water to one drop, or part,
solution. This means that each cup was 1/10 as concentrated as the cup before it. You may wish to show
Transparency 24.1, “Diluting and Testing Copper
Chloride,” to review the Procedure. To determine
the concentration in Cup 2 the denominator is
increased by a factor of 10; do this by multiplying
the denominator 10 (the concentration in Cup 1)
by 10. The concentration in Cup 2 is 1/100, or one
part in 100. Use optional Student Sheet 24.3, “Diluting Used Copper Chloride Solution to 1 PPM Copper,” to demonstrate this concentration. Concrete
models, like one penny in a dime compared to one
penny in 10 dimes, can help you explain this idea. It
is important to point that this visual model may
promote the misconception that not every part of a
solution contains the substance in question. Be sure
to emphasize that in a solution every drop contains
some amount, even a minuscule amount, of the
substance being measured; all of these amounts
contribute to the total concentration of a substance
in a solution. This concept will be developed further
in Unit C, “Water,” of Issues and Physical Science.
You may need to review with students how to convert 1/100 to 10,000/1,000,000. Then point out that
10,000/1,000,000 means 10,000 parts per million.
Explain that many substances that people are concerned about in the environment (lead, copper,
and mercury, for example) are present in relatively
low amounts. If these concentrations were
expressed as fractions, such as 10,000/1,000,000, it
would cumbersome. Parts per million is clearer and
simpler.
B-143
Activity 24 • Diluting the Problem
Sample Student Results for Student Sheet 24.1, “Determining Concentration”
Color of solution
Cup
6.
Copper chloride
+ water
Copper chloride
+ water + ammonia
Concentration
In parts per million
(ppm)
As a fraction
As a simplified
fraction
1
Green
Milky green
to blue
100,000
100,000
1,000,000
1
10
2
Light green
Dark blue
10,000
10,000
1,000,000
1
100
3
Colorless
Light blue
1,000
1,000
1,000,000
1
1,000
4
Colorless
Slight blue tint
100
100
1,000,000
1
10,000
5
Colorless
Colorless
10
10
1,000,000
1
100,000
6
Colorless
Colorless
1
1
1,000,000
1
1,000,000
7
(Water)
Colorless
Colorless
0
0
0
9
(Used
copper
chloride
solution)
Green
Milky green to blue
about 100,0000
100,000
1,000,000
1
10
The class discusses dilution as a treatment
for the used copper chloride.
Project Transparency 24.2, “Treating Waste Concept Map.” Explain that in this activity students
considered one way to treat the used copper chloride waste from Activity 23, “Producing Circuit
Boards” —dilution. In this, and in the next series of
activities they will explore three more methods of
dealing with the waste —incineration, precipitation
with solids, and precipitation with liquids. As a way
to keep track of what they are learning about each
method, and as a tool to help them with their final
decision about how to treat the waste, they will
record information about each method on Student
Sheet 24.2, “Treating Waste.” As a class, fill out the
“Dilution” column to summarize the treatment
method. Sample student answers are shown on the
next page.
For Analysis Question 2, make sure that students
have come to the understanding that toxic waste is
not always visible in a solution when in low concentrations. This creates the need for a test like the
ammonia test.
B-144
It is possible that students will find a variety of ways
to work through the calculations to answer Analysis
Question 4. Allow them to explore different methods. If they need support, consider passing out
optional Student Sheet 24.3, “Diluting Used Copper
Chloride Solution to 1 PPM Copper.”
If you decide to do so, be sure to explain that this
dilution sequence is specific to a 100,000-ppm
solution.
It may help students understand the quantities of
water described in Analysis Questions 4 and 5 if you
express them in terms of the water needs for a family of four. Most families of four can get along comfortably on 1,000 liters (250 gallons) of water per
day, not counting outdoor applications, such as
watering the garden. You might display a 2-L soft
drink bottle to help students imagine 500 2-L containers being delivered to their houses each day to
meet their basic water needs. At this level, a family
of four uses approximately 30,000 liters (7,500 gallons) of water per month. That is equivalent to
15,000 2-liter bottles! To dilute one liter—just one
Diluting the Problem • Activity 24
Sample Student Responses to Student Sheet 24.2, “Treating Waste” (Results for Dilution)
Dilution
Summary of
method
Adding water to lower
the concentration of
waste in a solution
Does it involve
a chemical
change?
No
Incineration
Reclaim
using solids
Reclaim
using liquids
Easy to add water
Positives
Can then release waste
into water system
Need a huge volume of
water to reduce to
nontoxic levels before can
be put down drain
Negatives
Heavy metals, even if
diluted, build up to
unhealthy and toxic
levels in waterways and
harm ecosystems and
humans
liter—of 100,000 ppm toxic waste to 1 ppm would
require the same amount of water that the family of
four uses in three months. The quantities of toxic
copper chloride waste produced by various industrial processes are much greater than one liter—
we’re talking about thousands and millions of
liters. The amount of water needed to dilute only
100 liters of 100,000 ppm used copper chloride solution to a safe level of less than 1 ppm is the same as
a family’s water needs for over 27 years! That’s a lot
of water that a manufacturer would need in a short
amount of time. This explanation can lead into a
discussion of Analysis Question 6.
Analysis Questions 5 and 6 turn students’ attention
from determining the concentration of copper in a
solution to using dilution as a disposal option for
the copper-containing waste generated when manufacturing circuit boards. Use students’ answers to
these questions to discuss with the class the option
of diluting, and then pouring the used copper chloride solution down the drain. Encourage students to
look up local guidelines for Analysis Question 6, as
prompted in the extension, and to incorporate
those into their answers. Students often think that
dilution is an acceptable strategy for disposing of
potentially toxic waste. Point out that a growing
body of scientific evidence shows that dilution as a
technique for dealing with solid, liquid, or gaseous
wastes has had varying degrees of success. One
important point for students to keep in mind is that,
regardless of the concentration, the total amount of
toxic waste released into an aquatic environment
(stream, river, lake, or ocean) remains the same for
heavy metal substances such as copper, mercury,
and lead. Thus, even if the concentrations of the
metals are minute when they are disposed of by
dilution, they accumulate in ecosystems, eventually
threatening humans and animals. Because the
major goal of pollution prevention is to reduce the
amount of toxic materials released into the environment, dilution is not usually an effective option for
wastes that are particularly hazardous.
Today, it is illegal to dispose of copper solutions
above a certain concentration and volume by pouring them into drains, sewers, or bodies of water. In
most areas, local water districts establish and
enforce these standards, which limit the concentration of copper that can be deposited into the sewers
from one source in a single day to 1–10 ppm. Many
municipal wastewater treatment plants are not
equipped to reduce the copper concentration low
enough to be considered safe.
B-145
Activity 24 • Diluting the Problem
EXTENSION
4.
The extension challenges students to find information about the local limits for copper disposal down
the drain. Encourage them to contact local Enviornmental Protection Agencies, or school district officials to find this information. This information can
be used to lead a class discussion on whether the
used copper chlroide waste can be poured down the
drain once it is diluted.
It would take 99,999 liters of water to dilute 1
liter of the copper solution to less than 1 ppm.
Answers to the optional Student Sheet 24.3,
“Diluting Used Copper Chloride Solution to 1
ppm Copper,” are shown on the next page.
5.
SUGGESTED ANSWERS TO QUESTIONS
1.
Which contains a more dilute solution, Cup 1
or Cup 2? Explain.
The solution in Cup 2 is less concentrated
because it is the 100,000 ppm copper chloride
solution from Cup 1 with water added to dilute it.
2.
Was there copper in Cups 1-6? How did you
know it was or was not there? Explain, using evidence from this activity.
When first observing the color of the solutions, it
appeared that cups 1 and 2 were the only ones
that had copper. Then, when the ammonia indicator was added, it showed that copper was
present in cups 1, 2, 3, and 4.
3. What is the concentration of copper in the class’s
used copper chloride solution from Activity 23, “Producing Circuit Boards”? Use the evidence from the
activity to support your answer.
The concentration of the copper is about
100,000 ppm. I know this because the color of
Cup 7 was closest to the color of Cup 1 when I
added the ammonia indictor, and Cup 1 has a
concentration of 100,000 ppm.
B-146
How many liters of water would you need
to dilute 1 liter of used copper chloride
solution from 100,000 ppm of copper to less than 1
ppm?
Based on your answers to Analysis
Questions 3 and 4, how many liters of
water would it take to dilute your waste from Activity
23, “Producing Circuit Boards,” to 1 ppm, an
acceptable concentration to pour down the drain?
According to the calculations in Analysis Questions 3 and 4, it would take 99,999 liters of water
to dilute 1 liter of the copper waste solution to
1ppm.
6. Is dilution an acceptable way to dispose of the used
copper chloride solution?
It would take a lot of water to dilute a very little
bit of waste. So it is not really feasible for a company that is producing circuit boards, unless
they are willing to incorporate large volumes of
water, which does not seem good for the environment either. Also, even though the amount
of copper is smaller, relative to the amount of
water when diluted, the copper will end up
down line in the water system and may accumulate in another part, harming an ecosystem.
Diluting the Problem • Activity 24
Sample Answers to Student Sheet 24.3, “Diluting Used Copper Chloride Solution to 1 ppm Copper”
1 liter of
100,000 ppm
copper solution
+
9 liters of
water
=
10 liters of
10,000 ppm
copper solution
10 liters of
10,000 ppm
copper solution
+
90 liters of
water
=
100 liters of
1,000 ppm
copper solution
100 liters of
1,000 ppm
copper solution
+
900 liters of
water
=
1,000 liters
of
100 ppm copper
solution
1,000 liters of
100 ppm copper
solution
+
9,000 liters
of water
=
10,000 liters
of
10 ppm copper
solution
10,000 liters
of
10 ppm copper
solution
+
90,000 liters
of water
=
100,000 liters
of
1 ppm copper
solution
B-147
©2007 The Regents of the University of California
Issues and Physical Science • Transparency 24.1
B-149
Treating Waste Concept Map
Manufacturing
processes
produce
Waste
treatment options
treatment options
Reuse
Disposal
reclaim
through
Incineration
Dilution
Precipitation
Metals
Solutions
©2007 The Regents of the University of California
2461 LabAids SEPUP IAPS TG
Figure: PhysTG B 28.01Trans
LegacySansMedium 10/11.5 (and bold)
Issues and Physical Science • Transparency 24.2
B-151
Name
Date
Determining Concentration
Color of Solution
Cup
Copper
Chloride
+ Water
Copper
Chloride
+ Water
+ Ammonia
1
Concentration
In parts
per million
(ppm)
As a fraction
As a
simplified
fraction
100,000
2
3
4
5
©2007 The Regents of the University of California
6
7
(Water)
9
(Used copper
chloride
solution
Issues and Physical Science • Student Sheet 24.1
B-153
Issues and Physical Science • Student Sheet 24.2
Negatives
Positives
Does it involve a
chemical reaction?
Summary of
method
Dilution
©2007 The Regents of the University of California
Incineration
Reclaim using solids
Reclaim using liquids
Name
Date
Treating Waste
B-155
Name
Date
©2007 The Regents of the University of California
Diluting Used Copper Chloride Solution to 1 ppm Copper
1 liter of
100,000 ppm
+ 9 liters
copper solution
of water
= 10 liters of
10,000 ppm
copper solution
10 liters of
10,000 ppm
+ 90 liters
copper solution
of water
= 100 liters of
_____ ppm
copper solution
100 liters of
_____ ppm
___ liters
_____ liters of
+
=
copper solution
of water
_____ ppm
copper solution
_____
liters of
_____ ppm
___ liters
_____ liters of
+
=
copper solution
of water
_____ ppm
copper solution
_____ ppm
___ liters
_____ liters of
+
=
copper solution
of water
1 ppm
copper solution
_____
liters of
Issues and Physical Science • Student Sheet 24.3
B-157