Grade 7: Mixtures and Solutions
Lesson: Potash Solution Mining – Dissolving Potash
Overview
Students will discover through guided inquiry and hands on activities that one of Saskatchewan’s valuable
mineral resources is a mechanical mixture which is mined by conventional underground methods or by
dissolution in water. The students will carry out activities to simulate the work of a Chemical
Engineer/Geochemist/Chemist /Chemical technician and general operations personnel in determining
how to mine potash deposits that are too deep to mine conventionally, how to separate the soluble
minerals from the insoluble minerals.
Source: This lesson plan has been adapted from an
activity developed by Murray Schultz (Chief Chemist,
Mosaic Potash) for the SMA Teacher GeoVenture Tour
and Showcase 2008, and from a lesson plan developed
by Larry Bogdan (Teacher, Avonlea School, Prairie South
School Division).
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Brainstorming
Discussion
Small group work
Guided inquiry
Laboratory investigation
Duration: 2 classes
Dredge on cooling pond. Mosaic Potash Belle Plaine
Materials:
 Clear glass canning jar(250ml) or glass beaker per
group
 250 ml measuring cup or graduated cylinder
 One litre container
 Potash sample (sylvinite) per group (approximately
3cm x 3cm)
 Room temperature water - 200 ml
 Weighing balance
 Coffee filter paper one per group
 One plastic coffee filter holder or a large funnel (more
would make the activity proceed more quickly)
 One litre container (to collect filtered solution)
 Spoon or plastic stir stick per group
 Student Activity and Observation Sheet
 Teacher Activity and Observation Sheet Answers
 Photos
 Potash Solution Mining in Saskatchewan diagram
Photo: Mosaic Potash Belle Plaine
Prior Knowledge:
Before attempting these activities students should have
some understanding of the following:
 Factors that affect solubility
 Saturated and unsaturated solutions
 The use of water as a solvent
Instructional Methods:
Learning Outcomes and Indicators
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
MS7.1 Distinguish between pure substances and
mixtures (mechanical mixtures and solutions) using the
particle model of matter. [SI]
 Will examine samples of potash ore and materials
produced through dissolution and record qualitative
(e.g., colour, texture, and state of matter) and
quantitative (e.g., solubility) physical properties of
those objects in a chart. (MS7.1a)
 Describe the characteristics of the pure substances
(mineral precipitates), mechanical mixtures (potash
ore), and solutions (dissolution of potash ore in water).
(MS7.1b)
 Create a solution using potash ore and water and
compare the physical properties of the original
materials and the resultant solution and precipitates.
(MS7.1f)
MS7.2 Investigate methods of separating the
components of mechanical mixtures and solutions, and
analyze the impact of industrial and agricultural
applications of those methods. [SI, TPS]
 Describe the methods used to separate minerals in the
potash ore (mechanical mixtures) using dissolution,
filtration, evaporation, and precipitation. (MS 7.2a)
MS7.3 Investigate the properties and applications of
solutions, including solubility and concentration. [SI,
DM]
 Identify which substance is the solute and which is the
solvent during the dissolution of potash ore. (MS7.3a)
 Describe the characteristics of solutions using the
terms solute, solvent, soluble, and insoluble, based on
the particle model of matter. (MS3.b)
 Investigate the factors that determine how quickly a
solute dissolves in a solvent. (MS3.e)
Source: Saskatchewan Evergreen Curriculum
Students will also:
 Discover that the potash mineral mined in
Saskatchewan is a salt and can be mined and
separated from other minerals through dissolution.
 Carry out an activity to simulate the work of a
Chemical engineer/Geochemist/Chemist/Chemical
technician and general operations personnel in
determining how to separate the valuable potash from
the potash ore.
 Discover how Geochemists, Chemical Engineers,
Chemists and Chemical technicians study and apply
scientific knowledge related to solutions.
 Understand that the Geochemists, Chemical
Engineers, Chemists and Chemical technicians work
along with the general operations personnel (it is a
team effort) in the development of mining methods
for potash, monitoring the quality of the potash
produced and helping to find new and better ways to
improve production and processing of potash.
Big Picture Question
1. How is potash mined if it is too deep in the ground
to mine in the conventional underground method?
Background Information
Potash is a general term covering several types of
potassium salts, of which the most important is
potassium chloride, the mineral sylvite (KCl). In
Saskatchewan, potash is extracted from deep
underground deposits (generally 1000 m or 1 km) using
either conventional (mining machines) or solution mining
(brine is used to remove the mineral in solution)
techniques.
The largest potash solution mine in the world is in
Saskatchewan. With this technique the potash is
dissolved deep underground and the solution is pumped
to the surface where the potash is removed. The same
process can be used above ground to extract the potash
from the sylvinite ore. After potash is mined, it is
processed in a surface mill, where it is separated into
product (KCl) and waste (tailings comprised of salt and
clays).
In 2010 there were 10 potash mines in Saskatchewan;
two are solution mines, and the remaining 8 are
conventional underground mines that use machines to
mine the ore.
Potash is a nutrient essential for plant growth, and is a
main component of modern agricultural fertilizers.
Roughly 95 per cent of world potash production goes
into fertilizer, while the other five per cent is used in
commercial and industrial products - everything from
soap to television tubes.
Potash is a major export of Saskatchewan. It is
transported by rail to the United States and to Canadian
ports where it is shipped to other countries including
China, Korea, Japan, Malaysia, India, Brazil and Australia.
Canadian markets make up less than 5% of potash sales.
Saskatchewan Mining Association www.saskmining.ca
Page 2
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
their observations prior to moving the jar/beaker to
work station. Continue on with the lab.
Safety concerns
 Do not eat potash sample
 Do not drink solution
1. Have students filter their mixtures by placing the
filter in a coffee filter holder/funnel and carefully
pour all of their solution and the insoluble products
into the filter. If insoluble particles remain in the
jar/beaker use some of the solution to rinse them
out.
Vocabulary
brine
density
halite
ore
Saturated/unsaturated
solution
sylvinite
dense
dissolve
mixture
potash
solute
solvent
sylvite
The solution can be washed down the drain or
collected in a bucket and disposed of down the drain
at a later time. Filters will need to be left to dry, possibly
over night.
If you are going to do the lesson Recovering Dissolved
Potash, keep one litre of the filtered solution.
THE ACTIVITY
Dissolving Potash
(Brainstorming, Hands-on lab) (80 minutes)
Motivational Set (10 minutes)
Inform the students that they are working as
Geochemists, Chemical Engineers, Chemists and
Chemical technicians for a potash company and that it is
their job to determine how to separate the valuable
potash mineral from the potash ore. Explain that potash
ore (sylvinite) is a mixture of halite (NaCl, table salt),
sylvite (KCl), clays and iron minerals. Write the formulas
for the two salts (NaCl (halite) and KCl (sylvite)) on the
board. Discuss the properties of table salt (NaCl) guiding
the students to the conclusion that it can be dissolved in
water. Inform the students that sylvite (KCl) is also a
salt., and that the potassium chloride is the valuable
mineral that the mining company wants but has to
determine a way to separate it from the clay and iron
minerals before they can separate it from the halite.
Brainstorm various methods of separating the potash
from the other undesirable insoluble minerals (clays, iron
minerals).
The students should come up with the answer: by
dissolving the salts and then separating the clay and
iron minerals.
Part 1 (Observation of dissolution of potash) (30 min.)
1. Have students work in pairs.
2. Hand out Student Activity and observation sheet and
have students do the lab activity.
Part 2 Filtration of mixture (40 min.)
At the beginning of the next class have students record
2. Have one person in the class weigh a clean dry filter.
This weight will be used as a standard weight for all
filters used.
3. When the student’s filters are dry, have each group
weigh their own filters with residue and record.
4. Students can then calculate the amount of the
insoluble materials in their sample.
5. Students can complete the discussion questions.
6. Have students post their answers to question 3 on
the board. As an extension students could do mean,
median and range of values.
7. Review the discussion questions.
Assessment Method and Evidence
 Anecdotal notes and/or checklist
 Students will show an ability to work together in a
cooperative learning environment.
 Discussion questions:
 Students will be able to explain that the potash
mineral mined in Saskatchewan is a salt which can
be mined and separated from other minerals
through dissolution in warm water.
 Students will be able to explain using their prior
knowledge of solutions and the solubility of salt to
come to the conclusion that the potash can be
separated from the ore waste through dissolution
 Students will be able to describe the solution
method used to separate the potash ore
(mechanical mixtures) from the waster rock using
dissolution, filtration, evaporation, and
precipitation.
Saskatchewan Mining Association www.saskmining.ca
Page 3
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
 Students will be able to identify which substance
is the solute and which is the solvent during the
dissolution of potash ore.
 Students will discover that stirring the materials
resulting from the partial dissolution of the ore
material will increase the speed and the amount
of dissolution.
 Students will be able to discuss some of the
consequences of solution mining such as what to
do with the remaining salt solution.
 Calculation Sheet:
 Students will weigh their sylvinite samples and
residue and calculate the percent of dissolved salts
and insoluble materials in their sample using
quantitative measurements.
 Hands on Activity:
 Students will take a sample of potash ore and
separate the soluble salts from the insoluble
waste materials through dissolution and
precipitation.
 Observation Chart:
 Students will describe the solution, resulting from
the dissolution of sylvinite, using qualitative terms.
 Students will describe the sample of potash ore
and the insoluble waste materials.
Technician, Chemist, and Geochemist by going to
Future Paths
http://www.futurepaths.ca/storage/CareerTreeMining.pdf
2. Have students investigate the uses of potash through
a web search of Saskatchewan’s potash companies:
Resources
Mining and milling processes used at the PotashCorp
mines.
http://www.potashcorp.com/media/POT_Mini_Mine_To
ur_brochure.pdf
Saskatchewan Potash Interpretive Centre:
http://www.potashinterpretivecentre.com/index2.htm
Saskatchewan Mining Association Website:
http://www.saskmining.ca
Potash Corporation of Saskatchewan Website:
http://www.potashcorp.com/
International Fertilizer Association Website:
http://www.fertilizer.org/ifa/default.asp
Agrium Website: http://www.agrium.com
 Journal Entry:
 Student will show their understanding of potash
solution mining in Saskatchewan and what role
the Geochemist/Chemical Engineer/Chemist plays
in the production of potash.
Summary
In a combination of guided inquiry and hands on
laboratory, students investigated how to mine potash
deposits that are too deep to mine conventionally and
how to how to separate the insoluble waste minerals
from the soluble salt minerals which includes the
valuable potash mineral sylvite (KCl). This activity
simulated some of the work of a Geochemist/Chemical
Engineer/ Chemist/ Chemical technician and general
operations personnel at a potash solution mine.
The Mosaic Company Website:
http://www.mosaicco.com
Fuzesy, A. (1981): Potash in Saskatchewan;
Saskatchewan Energy and Mines Report No.181, 44p.
Holter, M.E. (1969): The Middle Devonian Prairie
Evaporite of Saskatchewan; Department of Mineral
Resources-Geological Sciences Branch-Industrial
Minerals Division-Province of Saskatchewan; Report
No.123, 134p.
Storer, J., (1989): Geological History of Saskatchewan;
Saskatchewan Museum of Natural History. Regina:
Government of Saskatchewan, 90p.
Extension Activities
1. Students could investigate a career as a Chemical
Engineer, Chemical Technologist, Chemical
Saskatchewan Mining Association www.saskmining.ca
Page 4
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Teacher Answer Sheets Dissolving Potash
Background: Potash is one of the major exports of Saskatchewan. The potash minerals sylvite is a salt (KCl) that is
found in the potash ore sylvinite. The mining companies need to separate the KCl from the rest of the ore in order
to sell it.
Problem: How can the potash mineral (KCl) be separated from its ore? What properties are used to do this?
Hypothesis: (the hypothesis should be written as “if…then” and should include some explanation). Answer
Question 1 in Discussion.
If we place the potash ore in water then the salts (potash) will dissolve and can be separated from the insoluble
portion of the ore.
Materials: Clear glass canning jar(250ml) or glass beaker , Measuring cup or graduated cylinder, lump of potash
(sylvinite), 200 ml room temperature water, thermometer, weighing balance, filter, paper, spoon.
Procedure:
Part 1.
1. Measure 200 ml of room temperature tap water into a 250 ml jar/beaker. Put your names on the jar.
2. Weigh your potash ore (sylvinite) samples. Record weight
3. Carefully place your sample of sylvinite into the jar/beaker. Do not shake or stir the jar/beaker.
4. Over a period of 10-30 minutes observe what is happening in the jar/beaker and record on your
observation sheet. A drawing may be helpful.
5. Explain what is happening to the potash sample when it is immersed in the tap water.
6. Place jars/beakers in a safe place (shelf/counter) where they will not be disturbed until the next
class. Make observations throughout the day or wait until the next science class. Record your
observations including time and date.
Part 2
1. At the beginning of the next class record your observations before moving the jar/beaker.
2. Stir the mixture to break up any of the bigger pieces and record your observations.
3. Use a ball point pen to put your names on the coffee filter. Label the filter #1.
4. When your turn is called, place your filter into the coffee filter holder/funnel. Carefully stir the contents of the
jar and pour it all into the filter trying to get all of the remaining material into the filter. If insoluble particles
remain in the jar/beaker use some of the solution to rinse them out. DO NOT USE WATER.
5. Record your observations of the materials in the filter.
6. Leave the filters to dry until the next class.
7. Work on Discussion questions 2-5.
Part 3
1. Record the weight of the clean dry filter on your results sheet.
2. Weigh your own filter with residue and record (see Calculations sheet)
3. Determine the amount of the dissolved salts and the insoluble materials in your sample. See the
calculations on your results sheet.
4. Complete the discussion questions.
Teacher Answer Sheet: Dissolving Potash
Saskatchewan Mining Association www.saskmining.ca
Page 5
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Results:
Part 1.
Weight of filter
Weight of sample
OBSERVATIONS
Time
Observations
Start to 5 minutes
Tiny bubbles rise to the top, the colours of the sample are more distinct, tiny
white flecks like dust moved off the sylvinite and sank, white flecks are rising to
the surface.
Looking closely at the face of the potash ore there is a “wavy, flowing” look.
This is the salt on the edge of the sample dissolving in the water. As the water
dissolves the crystals you will see small cloud like eddies form which appear to
fall down to the bottom of the beaker.
10 to 15 minutes
Larger red particles are rising and sinking, most particles are less than a
millimetre, the surface of the ore is rougher and the clearer crystal part seems to
be disappearing, there is a reddish layer about the same depth as the top of the
ore and when sinking red particles hit this layer they stop sinking.
* the amount of red iron oxide and grey clays will vary per sample
20 to 25 minutes
30 – 35 minutes
Larger flakes are rising and sinking, the ore looks rough, red and grey, red flakes
are accumulating on the surface, very little clear crystal is visible.
Lots of sediment is on the bottom around the remaining ore, more red particles
rising and sinking, more particles suspended at a level near the top of the ore
and not moving.
Other observations
Part 2. Next Day or two
Description of materials in
the jar
There are many air bubbles attached to the sides of the jar/beaker, some red
flakes are floating on the surface, some are suspended in the clear liquid, there
doesn’t appear to be a reddish liquid zone near the bottom anymore, where the
ore was on the bottom there is now a layer of red and grey sediment, all of the
clear crystals are gone.
Description of materials in
the filter (residue)
The residue is reddish with some grey materials. When dry it looks pink, powdery
with some oddly shaped white particles. (See photos)
Teacher Answer Sheet: Dissolving Potash
Saskatchewan Mining Association www.saskmining.ca
Page 6
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Calculations:
Weight of residue and filter paper: _______
- Weight of filter paper: _______
Weight of residue =________ (the minerals (insolubles) that did not dissolve in the water)
Weight of sylvinite ore: _______
- Weight of residue: _______
= _______ Weight of dissolve salts
% dissolved salts = (weight of dissolved salts/total weight of sylvinite sample X 100) = _______
% of insolubles = (weight of dry residue/total weight of sylvinite sample X 100)
= _______
The insoluble material is the waste rock. Mining companies do not make money from waste rock, so the
less there is in the ore the better.
Teacher Answer Sheet: Dissolving Potash
Saskatchewan Mining Association www.saskmining.ca
Page 7
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Discussion Questions: (answer in full and complete sentences)
Part One
1. What is your hypothesis?
If we place the potash ore in water then the salts (potash) will dissolve and can be separated from the
insoluble portion of the ore.
2. Examine your sample of potash ore. How many different substances can you see or find in your
sample?
Students should have three or four substances in their samples. A red mineral (iron oxide), grey
mineral (clay), clear grey/white mineral and a cloudy or milky white mineral (the salts NaCl and KCl).
3. What properties helped you decide that the substances were different? Explain.
If the students do not have previous knowledge of mineral identification they will not use the terms
lustre and crystal structure. Ore samples vary so the descriptions will also vary. Properties used will
be colour, clarity (clear or milky), lustre (shininess), and crystal structure (or shape).
4. Is the sylvinite a pure substance, a mechanical mixture or a solution? Explain what observations
allow you to make this conclusion? Sylvinite is a mechanical mixture. Sylvinite is a mixture of
different minerals that grew together when they formed. When the ore is under water it becomes
more apparent that it is made up of different substances with different colours. Red particles, grey
particles and the shiny crystals.
5. You observed some particles rising and some sinking. Explain why some particles rise and others
sink.
Particle will rise if they are less dense than the liquid (some may be less dense because they have air
bubbles attached to them). Particles will sink if they are denser than the liquid. Students will probably
use the term heavy instead of dense. You can demonstrate what is happening with eggs and beakers
of water and salt solution. An egg will sink in a beaker of tap water but will float in a beaker of
concentrated salt solution.
DEMO: Dissolve as much table salt as you can in a beaker of water to form a concentrated or even
saturated solution. Next pour a beaker half full of concentrated salt solution and let it sit undisturbed
until the liquid has stopped moving. Hold a bent spoon (90° bend) at the surface of the salt solution
and gently pour water onto the convex surface of the spoon so that it forms a layer of pure water
above. Gently place an egg into this top layer and it will sink but float on the bottom layer. The top
layer of water is less dense than the egg but the layer of salt water is more dense than the egg. If you
mix the two layers the egg will sink to the bottom or float to the top depending on the final salt
concentration.
Part Two
1. You observed a pinkish layer near the bottom of the beaker. Why would sinking particles stop
sinking when they hit this layer? What causes this layer to form? What substance makes this layer
different from the surface layer?
The pink layer formed as the ore was dissolving. The sinking red particles are clay. They are red due
to an iron (hematite) coating. Sinking red particles would stop sinking when they hit this layer
because they are less dense that the pinkish layer. The reason for this is that as salt dissolves in to
the water it adds weight to the water (now a brine). As a result the more salt that dissolves the
heavier the brine gets which causes it to sink to the bottom. As the brine sits over time the salt ions
Teacher Answer Sheet: Dissolving Potash
Saskatchewan Mining Association www.saskmining.ca
Page 8
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
tend to settle down and form a density gradient which goes from least dense at the top to the most
dense at the bottom of the beaker.
2. What is the major property difference between the residue substances and the salts that allows you
to separate them using water and a filter?
The major property difference between the residue and the salts is solubility. The residue substances
are not soluble so their particles stay clumped together and cannot pass through the holes in the
filter. The particles of the salts dissolve and become separated into small individual particles that can
pass through the holes in the filter with the water
3. What percent of the sylvinite is insoluble? What percent is soluble? (See your calculation)
4. How do your answers for question 3 compare with your classmate’s answers? Answers should vary
somewhat. As an extension have the class do mean, median and range of values.
5. Your piece of sylvinite was just a small sample of a potash ore body. Why is the percent composition
of a small sample taken from a mechanical mixture not always the same?
Samples from a mechanical mixture are usually different because some samples may have bigger
amounts of one of the substances. The amounts of the substances are not constant.
6. What is a factor that determines how quickly a solute dissolves in a solvent?
Stirring or shaking the mixture in the solution increases the rate of dissolution.
Note to Teacher: Conclusion and Science Journal questions can be done here if not continuing on to
Activity Two. If continuing on, Conclusion and Science Journal questions can be answered after
Activity Two or Three.
Conclusions:
Your conclusion should include:
a) How the potash minerals were separated from the rest of the potash ore.
b) What property allows this to happen?
The salt minerals in potash ore can be separated from the ore by dissolving the ore in water and
passing it through a filter. The property is solubility. The salts KCL and NaCl are soluble in water.
Science Journal Questions:
1. Why is potash so important?
Potash is used in fertilizers as well as in TV. picture tubes, glass, rocket fuel, water softener, drilling
mud, and to melt ice.
The potassium, that comes from the potash, helps plants use water and resist drought. Potassium is
important to food crops and enhances the size of fruits and vegetables. It is called the regulator of
plants.
2. What is one of the jobs the potash company Geochemist/Chemical Engineer/Chemist does?
3. What courses do you think these scientists/technicians need to be good in?
4. What information have you learned in grade 7 science that would help you have a career with a
potash company?
5. Is this a career that you might be interested in?
Teacher Answer Sheet: Dissolving Potash
Saskatchewan Mining Association www.saskmining.ca
Page 9
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Student Activity Sheet Dissolving Potash
Background: Potash is one of the major exports of Saskatchewan. The potash mineral sylvite is a salt
(KCl) that is found in the potash ore sylvinite. The mining companies need to separate the KCl from the
rest of the ore in order to sell it.
Problem: How can the potash mineral (KCl) be separated from its ore? What properties are used to do
this?
Hypothesis: (the hypothesis should be written as “if…then” and should include some explanation).
Answer Question 1 in Discussion.
Materials: Clear glass canning jar(250ml) or glass beaker , Measuring cup or graduated cylinder, lump of
potash (sylvinite), 200 ml room temperature water, thermometer, weighing balance, filter
paper, spoon.
Procedure:
Part 1.
1. Measure 200 ml of room temperature tap water into a 250 ml jar/beaker. Put your names on the jar.
2. Weigh your potash ore (sylvinite) samples. Record weight
3. Carefully place your sample of sylvinite into the jar/beaker. Do not shake or stir the jar/beaker.
4. Over a period of 10-30 minutes observe what is happening in the jar/beaker and record on your
observation sheet. A drawing may be helpful.
5. Explain what is happening to the potash sample when it is immersed in the tap water.
6. Place jars/beakers in a safe place (shelf/counter) where they will not be disturbed until the next
class. Make observations throughout the day or wait until the next science class. Record your
observations including time and date.
Part 2
1. At the beginning of the next class record your observations before moving the jar/beaker.
2. Stir the mixture to break up any of the bigger pieces and record your observations.
3. Use a ball point pen to put your names on the coffee filter. Label the filter #1.
4. When your turn is called, place your filter into the coffee filter holder/funnel. Carefully stir the
contents of the jar and pour it all into the filter trying to get all of the remaining material into the
filter. If insoluble particles remain in the jar/beaker use some of the solution to rinse them out. DO
NOT USE WATER.
5. Record your observations of the materials in the filter.
6. Leave the filters to dry until the next class.
7. Work on Discussion questions 2-5.
Part 3
1. Record the weight of the clean dry filter on your results sheet.
2. Weigh your own filter with residue and record (see calculations)
3. Determine the amount of the dissolved salts and the insoluble materials in your sample. See the
calculations on your results sheet.
4. Complete the discussion questions.
Student Sheet: Dissolving Potash
Saskatchewan Mining Association www.saskmining.ca
Page 10
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Results:
Part 1.
Weight of filter
Weight of sample
OBSERVATIONS
Time
Name:____________________
Observations
Start to 5 minutes
Part 2. Next Day
Description of materials
in the jar
Description of materials
in the filter (residue)
Student Sheet: Dissolving Potash
Saskatchewan Mining Association www.saskmining.ca
Page 11
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Calculations:
Weight of residue and filter paper: _______
- Weight of filter paper: _______
Name:_____________________
__________________________
_
= Weight of residue: ________ (the minerals that did not dissolve in the water)
Weight of sylvinite ore: _______
- Weight of residue: _______
= Weight of dissolved salts: _______
% dissolved salts = (weight of dissolved salts/total weight of sylvinite sample X 100) = _______
% of insolubles = (weight of dry residue/total weight of sylvinite sample X 100)
= _______
Solute = __________g
Solvent = _________ ml
The insoluble material is the waste rock. Mining companies do not make money from waste
rock, so the less there is in the ore the better.
Student Sheet: Dissolving Potash
Saskatchewan Mining Association www.saskmining.ca
Page 12
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Name: _____________________
Discussion Questions:
Part One
1. What is your hypothesis?
2. Examine your sample of potash ore. How many different substances can you see or find in your
sample? Describe them.
2. What properties helped you decide that the substances were different? Explain.
3. Is the sylvinite a pure substance, a mechanical mixture or a solution? Explain what observations allow
you to make this conclusion?
4. You observed some particles rising and some sinking. Explain why some particles rise and others sink.
Part Two
1. You observed a pinkish layer near the bottom of the beaker. Why would sinking particles stop sinking when
they hit this layer? What causes this layer to form? What substance makes this layer different from the surface
layer?
2. What is the major property difference between the residue substances and the salts that allows you to separate
them using water and a filter?
3. What percent of the sylvinite is insoluble? What percent is soluble? (from your calculations)
4. How do your answers for question 3 compare with your classmate’s answers?
5. Your piece of sylvinite was just a small sample of a potash ore body. Why is the percent composition of a small
sample taken from a mechanical mixture not always the same?
6. What is a factor that determines how quickly a solute dissolves in a solvent?
Conclusions:
Your conclusion should include: a) How the potash minerals were separated from the rest of the potash ore.
b) What property allows this to happen?
Student Sheet: Dissolving Potash
Saskatchewan Mining Association www.saskmining.ca
Page 13
Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Science Journal Questions:
1. What is one of the jobs the potash company Geochemist/Chemical Engineer/Chemist does?
2. What courses do you think these scientists need to be good in?
3. What information have you learned in grade 7 science that would help you be a geochemist for a
potash company?
4. Is this a career that you might be interested in?
Student Sheet: Dissolving Potash
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Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Potash Solution Mining in Saskatchewan
2
1
From: Mosaic Potash PowerPoint –Showcase Belle Plaine
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Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Vocabulary
Brine: Water saturated with or containing large amounts of a salt, especially sodium chloride. The water
of a sea or an ocean is a brine.
Dense: Closely packed. Having relatively high density.
Density: The measure of the compactness of a substance, expressed as its mass per unit volume.
Dissolve: To break into component parts to become incorporated into a liquid so as to form a solution.
Halite: Sodium chloride (NaCl) as a mineral, typically occurring as colourless cubic crystals; what we know
as salt.
Mixture: is a material system made up by two or more different substances which are mixed together
but are not combined chemically
Ore: Is rock that contains important minerals including metals. The ore is extracted through mining and
processed to extract the valuable element(s). Ore contains minerals that can be mined at a profit.
Potash: Is Saskatchewan’s provincial mineral. Potash is the common name for the potassium rich ore
mined in Saskatchewan. It is made up of the minerals sylvite, halite, sometimes carnallite, clay and
iron oxides.
Saturated: If saturated, it has absorbed the maximum amount of something that it can.
Solute: A substance dissolved in solvent, forming a solution.
Solution: A liquid with something dissolved in it. It is a homogeneous mixture composed of two or more
substances. In such a mixture, a solute is dissolved in another substance, known as a solvent.
Solvent: is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute,
Sylvinite: is the most important ore for the production of potash in North America. It is a mechanical
mixture of sylvite (KCl, or potassium chloride) and halite (NaCl, or sodium chloride).[
Sylvite: is potassium chloride (KCl) in natural mineral form. It forms very similar to normal rock salt,
halite (NaCl). Sylvite is colorless to white with shades of yellow and red due to inclusions. It has a
Mohs hardness of 2.5. Sylvite has a salty taste with a distinct bitterness. Sylvite is one of the last
evaporite minerals to precipitate out of solution. As such, it is only found in very dry saline areas.
Its principal use is as a potassium fertilizer.
Waste rock: Barren or sub-marginal rock or ore that has been mined, but is not of sufficient value to
warrant treatment and is therefore removed ahead of the milling processes.
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Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Source:
Wikipedia. Available at: http://en.wikipedia.org/wiki/
Dictionary of Mining, Minerals and Related Terms. Available at:
http://xmlwords.infomine.com/xmlwords.htm
Oxford English Dictionary on-line: Available at: http://oxforddictionaries.com
Yahoo Kids: Available at: http://kids.yahoo.com/reference/dictionary/english/
Saskatchewan Mining Association www.saskmining.ca
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Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Photos
Sylvinite, potash ore sample – dry. Look as the size of
the minerals. You should see red (iron oxide), greybrown (clay), clear and white minerals (salt minerals
halite and sylvite)
Sometimes it is easier to see the minerals if the sample
is wet.
You will see the clay mineral start to fall apart in little
clumps. You may also see air bubbles on the sample.
This is air that was attached to the sample as it went
into the water or may be some air being released from
small fractures or holes in the sample.
When the sample is first put into the water it will start
to dissolve making the water cloudy. Some of the iron
oxide minerals will start to float to the top of the water.
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Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
This sample has a lot of clay (grey – brown). It has
dissolved into little chunks while the red oxided
minerals are floating in the solution.
Potash ore sample dissolving. The clay (grey – brown
minerl and the iron oxide mineral are visible but where
are the salt minerals?
Eventually the solution clears. Some of the red oxide
has sunk to the bottom and some remains floating on
the surface of the solution.
Layer of iron oxides
forming
Occassionaly you may see the development of density
layering. The iron oxides are floating on the more dense
salt-water solution.
To break up the clumps of clay shake the jar (with the lid on) or stir.
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Grade 7 Mixtures and Solutions: Potash Solution Mining: Dissolving Potash continued
Once the sediment has settle you will see layering with
the heavier clay minerals on the bottom and the lighter
oxide minerals on top as well as floating on the surface
of the solution.
A close up of the sediment layers.
The filtered material is fine grained but when dried may
have some crystals. Fine material is the clay and iron
oxide minerals (reddish). Larger white grains are salts.
The unsoluble minerals left in the filter. Wet.
When the residue is dry the minerals that crystallized can be irregular in shape.
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