Separation of a Mixture of
Solids
Hands-On Labs, Inc.
Version 42-0196-00-02
Review the safety materials and wear goggles when
working with chemicals. Read the entire exercise
before you begin. Take time to organize the materials
you will need and set aside a safe work space in
which to complete the exercise.
Experiment Summary:
You will learn about homogenous and heterogeneous
mixtures. You will learn how solubility and magnetism
are used to separate a mixture of solids into four pure
substances, and calculate the percent composition
of each pure substance.
EXPERIMENT
© Hands-On Labs, Inc. www.HOLscience.com 1
Learning Objectives
Upon completion of this laboratory, you will be able to:
● Define chemical elements and chemical compounds.
● Distinguish between homogenous and heterogeneous mixtures
● Explain solvent, solute, miscible, and immiscible.
● Compare and contrast solubility and dissolution.
● Discuss the nature of solutes and solvents.
● Demonstrate separation techniques using techniques involving solubility and magnetism.
● Determine the pure substances that comprised (make up) the mixture of solids.
● Estimate the percent composition of each pure substance that was present in the mixture of
solids.
Time Allocation: 2.5 hours, plus an overnight drying period
www.HOLscience.com 2 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Materials
Student Supplied Materials
Quantity Item Description
1 Aluminum pie pan
1 Bottle of distilled water
1 Bowl
1 Crushed ice
1 Matches or lighter
1 Oven mitt or kitchen towel
1 Pair of scissors
1 Plastic wrap
1 Roll of paper towels
2 Sheets of white paper
1 Source of tap water
HOL Supplied Materials
Quantity Item Description
1 Aluminum cup, 2 oz
1 Burner fuel
1 Burner stand
1 Digital scale, precision
1 Funnel, 70 mm
2 Glass beakers, 100 mL
1 Glass stirring rod
1 Graduated cylinder, 25 mL
1 Magnet bar, 1.00 x 0.23 in
1 Pair of gloves
1 Pair of safety goggles
1 Plastic cup, 9 oz
1 Ruler
1 Experiment Bag: Separation of a Mixture of Solids
1- Filter paper 12.5 cm
1- Mixture of solids – 5 g in Bag 2”x 3”
1- Weighing boat, plastic
www.HOLscience.com 3 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Note: To fully and accurately complete all lab exercises, you will need access to:
1. A computer to upload digital camera images.
2. Basic photo editing software such as Microsoft Word® or PowerPoint®, to add labels, leader
lines, or text to digital photos.
3. Subject-specific textbook or appropriate reference resources from lecture content or other
suggested resources.
Note: The packaging and/or materials in this LabPaq kit may differ slightly from that which is listed
above. For an exact listing of materials, refer to the Contents List included in your LabPaq kit.
www.HOLscience.com 4 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Background
Elements and Compounds
Elements are the simplest chemical substances and are composed of only one type of atom. The
periodic table is a listing of all elements. For example, hydrogen (H), oxygen (O), sodium (Na), and
chlorine (Cl) are all examples of elements. See Figure 1. Compounds are also pure substances,
but are composed of two or more elements bonded together in specific proportions: water (H
2
O)
and sodium chloride (NaCl) are compounds. Each element and compound has specific properties,
and both are considered to be pure substances; substances that cannot be further separated by
physical means. Compounds can only be separated into their component elements by breaking
chemical bonds.
Figure 1. Periodic Table. All items in the periodic table are elements, the simplest of the pure
substances. Click to Download Printable Version.
Mixtures
A mixture is a combination of two of more pure substances and can be either homogenous or
heterogeneous. A heterogeneous mixture is composed of visibly distinguishable parts and does
not have uniform composition. Examples of heterogeneous mixtures include a chopped salad,
water with pieces of lemon, the contents of a lava lamp, or a bowl of mixed nuts. In contrast,
a homogenous mixture is composed of visibly indistinguishable parts which have a uniform
composition. Examples of homogenous mixtures include cake batter (without lumps), chocolate
milk, and perfume.
www.HOLscience.com 5 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
http://holscience.com/sites/default/files/Periodic_Table.pdf
Panning for gold was very popular around the
turn of the 20th century and is still a popular
hobby and activity for many. Panning for gold is
a method that extracts gold from a heterogeneous
mixture. The mixture (sand, gravel, minerals, gold,
etc.) is gathered in a pan and sifted and panned
until all components of the heterogeneous mixture
have separated from the gold, allowing it to be
collected.
Another term for a homogenous mixture is a solution. A solution is a mixture where one substance
has been dissolved into another. Substances are defined as either solutes or solvents. A solvent
is the substance in which the solute is dissolved, forming a solution. A common example of a
solution (homogenous mixture) is salt water, where water (H
2
O) is the solvent and salt (NaCl) is
the solvent. While a solvent can be a solid, liquid, or gas, it is most commonly a liquid. In cases
where both the solute and solvent are liquids, they are said to be either miscible (soluble) or
immiscible (insoluble).
Solubility describes the capacity of a given chemical substance to fully dissolve with another, and
is dependent upon both concentration and temperature. The terms solubility and dissolution
are often used interchangeably, but they actually have distinct meanings. Solubility is the
maximum amount of solute that is able to be dissolved in a specific amount of solvent at a specific
temperature; thus it is defined in terms of concentration and is independent of rate. In contrast,
dissolution is a kinetic process defined by rate (how fast something happens), and not specific to
concentration. The main distinction between the two terms is that a substance can dissolve into a
solution as the result of a chemical reaction, but that same substance may not be soluble. Likewise,
solubility is not dependent on how fast a solute dissolves into a solvent; it is dependent on the
nature or properties of both the solute and solvent, as well as on the conditions of temperature
and pressure.
Nature of Solutes and Solvents
The nature of a solute and solvent is determined by both the chemical structure and properties
of the pure substance. Solutes and solvents can be roughly divided into two groups, polar and
nonpolar. Chemists have developed the general rule “like dissolves like” for determining solubility,
which means that polar solutes are most likely to dissolve into polar solvents, and nonpolar solutes
are most likely to dissolve into nonpolar solvents. For most solids dissolved in liquids (especially
H
2
O), solubility increases as temperature increases. For example, consider the ability of salt (NaCl)
and benzoic acid (C
6
H
5
COOH), both pure substances, to dissolve in water. See Figure 2.
www.HOLscience.com 6 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Figure 2. Solubility of salt and benzoic acid. Benzoic acid (C
6
H
5
COOH) is denoted in blue (▬)
and salt (NaCl) is denoted in red (▬). Both substances have increased solubility at higher
temperatures. Notice that benzoic acid is approximately thirtyfold more soluble at 95°C than at
0°C.
Both substances are soluble at higher temperatures, but differ in solubility at low temperatures.
Notice that NaCl is still quite soluble in cold water while benzoic acid’s solubility decreases
significantly in cold water. Thus, if both substances were mixed with water, they would create a
homogenous mixture at high temperatures, and a heterogeneous mixture at cold temperatures,
as the benzoic acid would crystallize out of solution as the temperature drops, while salt would
remain soluble.
There are numerous methods to separate pure substances from homogenous and heterogeneous
mixtures. In this experiment a mixture of solids will be separated by the properties of solubility
and magnetism. Magnetism is the force produced by a magnetic field, or the ability of a substance
to attract specific substances such as iron, nickel, or steel.
www.HOLscience.com 7 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Exercise 1: Separation of a Mixture
In this exercise, you will separate a mixture into four components using the properties of solubility
and magnetism.
Note: Some sections of this exercise require several days for drying and evaporation. Remember to
read all instructions before beginning.
Procedure
1. Gather the bag containing the mixture of solids.
2. Put on safety glasses and gloves.
3. Place the small weighing boat onto the scale and tare the scale so that it reads 0.00 g with the
weigh boat on the scale.
4. Carefully pour the contents of the bag into the weigh boat to obtain the mass of the mixture
of solids. Record this mass in Data Table 1 of your Lab Report Assistant.
5. Gather a clean sheet of white paper and pour the entire mixture of solids into a smooth layer
on the white paper. See Figure 3.
Figure 3. Mixture of solids spread across clean sheet of white paper.
6. Gather a second sheet of clean white paper and use the ruler and scissors to cut a 10 cm x 10
cm square of paper. Fold the sheet of paper in half. See Figure 4.
www.HOLscience.com 8 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Figure 4. Square of clean paper folded in half.
7. Place the folded paper on the scale to obtain the mass of the paper. Record the mass in Data
Table 1.
8. Gather the magnet bar and a piece of plastic wrap. Wrap the magnet in plastic wrap and hold
the magnet directly above the mixture of solids. Separate the iron filings from the mixture by
passing the magnet closely over the surface several times until all filings have collected onto
the magnet. See Figure 5.
Figure 5. Bar magnet, wrapped in plastic, collecting all iron filings from the mixture of solids.
www.HOLscience.com 9 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
9. Remove the iron filings from the magnet by holding the magnet with the iron filings over the
folded paper and carefully removing the plastic wrap from the magnet. As the plastic wrap is
separated from the magnet the iron filings will fall onto the paper.
10. Place the paper containing all of the iron filings onto the scale to obtain the mass of the paper
and iron filings. Record the mass in Data Table 1.
11. Subtract the mass of the paper from the mass of the paper and iron filings to obtain the mass
of the iron filings. Record this mass in Data Table 1.
12. Place the iron filings to the side, as they will not be used again in the experiment.
Note: You have finished separating the first of 4 mixtures.
13. Gather one of the clean, 100-mL glass beakers and place it on the scale to obtain the mass.
Record the mass in Data Table 1.
14. Transfer the remaining mixture of solids from the white paper into a clean, 100-mL glass
beaker.
15. Use the graduated cylinder to measure 50 mL of distilled water and pour the distilled water
into the glass beaker containing the remaining mixture of solids.
16. Stir the solids in the water with the glass stir rod.
17. Place the burner stand and burner fuel on the pie plate.
18. Uncap the burner fuel and light the wick with the matches or lighter.
19. Slide the burning fuel under the burner stand. See Figure 6.
Figure 6. Burner fuel setup.
www.HOLscience.com 10 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
20. Place the glass beaker containing the mixture and distilled water onto the burner stand and
stir the mixture with the stir rod until the mixture begins to boil.
21. When the mixture begins to boil, use the small, 2 oz aluminum cup to extinguish the burner
fuel flame. See Figure 7.
• Do not touch the metal stand or the beaker; they may be hot.
• Carefully slide the burner fuel canister out from underneath the burner stand. The
sides of the burner fuel canister will be warm, but not hot.
• Place the aluminum cup directly over the flame to smother it. The cup should rest on
top of the fuel canister, with little or no smoke escaping.
Figure 7. Using the aluminum cup to extinguish the flame.
22. Gather the clear, 9 oz. plastic cup.
23. Use an over mitt or towel to carefully lift the beaker from the stand and decant the liquid into
the clear, 9 oz. plastic cup by placing the stir rod in a horizontal position over the spout of the
beaker to help keep the solids from decanting into the plastic cup. See Figure 8.
www.HOLscience.com 11 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Figure 8. Decanting the liquid from the mixture. Note that small amounts of solid may transfer
with the decanted liquid.
24. When all liquid has been decanted, place the glass beaker containing the solid in a warm
location, where it will not be disturbed, and allow the remaining liquid to evaporate. This may
require an overnight waiting period, depending on the humidity of your location.
25. Rinse the glass stir rod with water and dry using paper towels.
26. Create an ice bath by placing ice cubes and water into the bowl. Carefully place the clear
plastic cup containing the decanted liquid into the ice bath, making sure the cup does not tip
over.
27. Allow the cup with the decanted liquid to remain in the ice bath for approximately 5 minutes
to evenly cool the solution.
Note: As the solution in the cup begins to cool, you will see the benzoic acid crystallizing out of
solution.
28. While the decanted liquid is in the ice bath, fold the round filter paper into a cone shape, as
shown in Figure 9.
www.HOLscience.com 12 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Figure 9. Folding of filter paper.
29. Place the folded filter paper onto the tared scale and record the mass of the filter paper in
Data Table 1.
30. Gather the second, clean 100 mL glass beaker and place it on the scale to obtain the mass.
Record the mass in Data Table 1.
31. Place the filter paper into the plastic funnel and the plastic funnel on top of the 100 mL glass
beaker.
32. After the cup containing the decanted liquid has been cooling for approximately 5 minutes,
carefully pour the decanted liquid (which now contains visible benzoic acid crystals) into the
filter paper, and allow the liquid to separate from the benzoic acid crystals.
33. Rinse the clear plastic cup with a small amount (approximately 5 mL) of distilled water to
dislodge any benzoic acid crystals stuck to the side of the cup and pour into the filter.
Note: It may take a few minutes for all of the liquid to flow through the filter paper. Slightly swirling
the plastic filter will help the liquid to flow through the paper.
34. When all of the liquid has collected in the 100 mL glass beaker, carefully remove the filter
paper from the plastic funnel and set it next to the beaker containing the sand in a warm
location, and allow the filter paper to completely dry. This may take overnight. See Figure 10.
www.HOLscience.com 13 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Figure 10. Filter paper with benzoic acid, next to beaker containing sand, sitting in a warm
location waiting for the water to evaporate.
Note: The liquid remaining in the second 100-mL beaker, which flowed through the filter paper,
contains the fourth substance in the mixture of solids.
35. Place the burner stand and burner fuel on the pie plate.
36. Uncap the burner fuel and light the wick with the matches or lighter.
37. Slide the burning fuel under the burner stand. See Figure 7.
38. Place the glass beaker containing the salt solution onto the burner stand and allow the water
to boil and evaporate from the salt solution. Watch this carefully and do not walk away from
the boiling solution.
39. When the salt begins to splatter along the sides of the beaker and the majority of the water
has evaporated, extinguish the burner by carefully placing the aluminum cup just over the
flame.
40. Allow the beaker to cool and the remainder of the water to evaporate. This may take overnight.
41. After all water has fully evaporated, weigh the beaker containing the sand and record the
mass in Data Table 1, weigh the beaker containing the salt and record the mass in Data Table
1, and weigh the filter paper containing the benzoic acid and record the mass in Data Table 1.
42. Determine the mass of each of the 3 substances by subtracting the mass of the beakers and
filter paper alone, from the mass of the beakers and filter paper with substances in them and
record the mass of each substance in Data Table 1.
Cleanup:
43. Discard the used filter paper and any leftover solids in the trash.
44. Wash and dry all other equipment and return to the lab kit for future use.
www.HOLscience.com 14 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
www.HOLscience.com 15 ©Hands-On Labs, Inc.
Experiment Separation of a Mixture of Solids
Exercise 2: Summary of Separation
You will estimate the percent composition of each pure substance that was present in the mixture
of solids.
Procedure
1. Transfer the necessary data from Data Table 1 of Exercise 1, into Data Table 2 of your Lab
Report Assistant.
2. Calculate the percent of total mixture for each substance by dividing the mass of the substance
by the mass of the mixture of solids and multiplying by 100. See equation below.
Questions
A. What percent of the total mass of mixture of solids (Initial) was recovered through the
separation techniques? (Hint: What was the percent difference between the sum of the four
separated components and the initial mass of the mixture of solids?)
B. Describe possible sources of error to account for any deviation between the percent of the
total mass of mixture of solids (initial) and the sum of separated components.
C. What was the most challenging step to perform in the separation procedure? What would
you suggest to make the step less challenging?