SEPARATING SALT, SAND AND IRON FILINGS
Benchmarks:
SC.5.P.8.3
Demonstrate and explain that mixtures of solids can be separated based on
observable properties of their parts such as particle size, shape, color, and magnetic attraction.
(Also assesses SC.5.P.8.2)
SC.5.N.2.1
Recognize and explain that science is grounded in empirical observations that are
testable; explanation must always be linked with evidence.
Objective/Purpose:
 Students will describe and/or explain how mixtures of solids can be separated.
 Students will identify common materials that dissolve in water.
 Students will identify or describe conditions that will speed up or slow down the dissolving
process.
Background Information: Iron is a magnetic solid and does not dissolve in water. Salt is not a
magnetic solid and dissolves in water. Sand is not a magnetic solid and does not dissolve in water.
Teacher Notes: In this activity students will learn that materials can be separated according to
differences in their physical properties. Some of the physical properties used in the activity will
include whether or not a substance is magnetic or whether or not a substance dissolves in water.
Engage: Hold up a small bottle of sand and another of white rice. Ask students to name some
properties of each. Now pour some of each into the same small beaker and stir. How have the
properties of each changed? What have we made? How could we separate them? Students may
suggest separating them by picking out the rice; have a student try this. What would be a faster
way? (Use a strainer.)
Explore: What physical properties could be used to separate a mixture of pepper, salt, sand, and
iron filings?
.
Materials:
 1 one-ounce cup with a mixture of salt, sand, and iron filings
 3 index cards
 2 plastic spoons
 1 magnet in a sealed plastic bag
 1 cone-shaped coffee filter
 100 mL of water in a graduated cylinder
 1 hand lens
 1 paper towel
 1 pair of safety goggles
 2 plastic cups
 1 strainer
Procedures:
1. Spread out the mixture on one of the index cards. Use the hand lens to observe the mixture
and identify the salt, sand, and iron filings. How can you tell their differences? Record your
observations and explanations in a data table #1.
2. Place the magnet in the sealed plastic bag under the index card. Move the magnet around
under the mixture on the index card. Slowly pull the magnet to the side. Take the magnet
away from the index card. Repeat this several times until you have separated one of the
ingredients from the mixture. The student doing this part should wear the safety goggles.
3. Carefully brush only the separated particles onto a clean index card.
4. Use the hand lens to observe the particles that were separated out of the solid mixture.
Record your observations about iron filings in data table #4.
5. Put the remaining mixture of salt and sand back into the plastic cup. Pour 100 mL of water
into the cup with the mixture. Stir it for 10 seconds with a plastic spoon.
6. Put the cone-shaped coffee filter in the other plastic cup.
7. Pour the mixture in the cup through the coffee filter in the other cup. Use the plastic spoon to
scrape out all of the mixture from the cup.
8. Carefully remove the coffee filter from the cup. Open up the filter. Use the hand lens to
observe what is in the coffee filter. Record your observations about the sand in data table #8.
9. Use the hand lens to observe what is in the second plastic cup (water). Record your
observations about the water in data table #9.
10. Leave the cup in a sunny window to allow the water to evaporate. After a several days, use the
hand lens to observe what is in the cup now. Record your observations in data table #10.
Have students record their observations for steps 1, 4, 8, 9, and 10 in the data tables below.
#1. Observations
#4. Observations
#8 Observations
#9. Observations
#10. Observations
Explain
1. What did you observe when you used the magnet to separate the solid mixture? Which
particles were separated out of the solid mixture by using the magnet?
____________________________________________________________________
____________________________________________________________________
2. When you stirred water into the mixture and poured it through the coffee filter, what
did you observe? What is the solid material in the coffee filter?
____________________________________________________________________
____________________________________________________________________
3. What did you observe in the cup after it had been left in the window for several days?
____________________________________________________________________
____________________________________________________________________
4. What physical properties did you use to separate a mixture of salt, sand, and iron
filings?
____________________________________________________________________
____________________________________________________________________
5. From conducting the experiment, I learned __________________________________
_____________________________________________________________________
_____________________________________________________________________
Extension:
Have students create a list of mixtures and solutions that they find in everyday life in their journals.
Then describe how they can be separated using the objects’ physical properties.
Possible examples include:
 In cooking, you normally skim off the oil/fat from the gravy or broth.
In cooking, you sometimes need to separate the egg yolk from the egg white to make
meringues.
 Separating into recyclables into groups of plastic, paper and glass for collection.
 Huge magnets are used to separate iron from other metals in scrap yards.
 In some places in the world, salt is evaporated from oceans to provide drinking water.