Experiment 3: Classification of Matter. Separation of Mixtures
Required reading:
-Matter: Physical state and chemical constitution
-Chromatography
-Significant Figures
-SI and derived units
- Percent composition
-Mole calculations
Learning Goals:
 To write a procedure and follow it.
 To design a protocol to separate a mixture, choosing appropriate glassware and
equipment.
 To record data in an organized manner.
 To correctly use measuring units and significant figures.
 To draw logical conclusions based on data.
 To use different separation techniques (filtration, evaporation, chromatography,
magnet).
 To classify matter.
 To keep a lab notebook and write an informal lab report.
Background information and theory:
Matter is anything that has mass and occupies space. Matter can be classified as
pure substances or Mixtures.
A pure substance can be subclassified in elements or compounds. Elements
combine chemically to form compounds.
Compounds and elements combine (without chemical change or reaction) to form
mixtures. Mixtures can be heterogeneous or homogeneous. A heterogeneous mixture is
one where the component of the mixture can be observed. Examples are trail mix, orange
juice with lots of pulp, water and sand. A homogeneous mixture, on the other hand, looks
like one substance since all the components are miscible (the mix together well) examples
are water and sugar, air.
Elements and compounds cannot be separated by physical means, however
mixtures can be separated by techniques as filtration, distillation, chromatography.
To learn more about matter watch the following video:
https://www.youtube.com/watch?v=ASMnfoe1Q-g
In this experiment we will use demonstrations and simulations to observe the
separation of mixtures using different separation techniques.
The first part will deal with the separation of a solid sample by using techniques
like filtration, evaporation, etc.
To learn more about filtration watch the following video:
https://www.youtube.com/watch?v=Q0s71cjCNWs
Analysis of the possible composition of the sample will be done in order to study
% recovered which measures how much of each component was separated from the
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original sample. Theoretical values and experimental values will be provided to perform
these calculations.
The percent recovered is calculated with the formula below and it is a
measurement of the efficiency of the separating method:
% 𝐴 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑 =
𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑚𝑎𝑠𝑠 𝑜𝑓 𝐴
𝑥100%
𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑚𝑎𝑠𝑠 𝑜𝑓 𝐴
Determination and analysis of % composition of the solid sample will be also
carried out in the first part of the experiment. The % composition (or mass%) is defined
as the mass of each substance divided by the total mass of the sample multiplied by 100.
𝑀𝑎𝑠𝑠 % 𝐴 =
𝑚𝑎𝑠𝑠 𝑜𝑓 𝐴 𝑖𝑛 𝑡ℎ𝑒 𝑠𝑎𝑚𝑝𝑙𝑒
𝑥100%
𝑡𝑜𝑡𝑎𝑙 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑎𝑚𝑝𝑙𝑒
Elemental analysis of mixture components and calculation of moles and atoms
contained in the mixture will be performed in this lab (postlab questions).
In the second part of the experiment chromatography will be used to separate two
liquid samples.
To
learn
more
about
chromatography
watch
the
following
video:
https://www.youtube.com/watch?v=gpFb635N2wo
All chromatography procedures contain a sample, a stationary phase and a mobile phase.
The stationary phase is a solid or liquid phase of a chromatography system on which the
materials to be separated are selectively adsorbed. The mobile phase is a liquid or gas
that flows through a chromatography system, moving the materials to be separated at
different rates over the stationary phase.
In paper or thin layer chromatography, samples are spotted on to a pencil line drawn on
a sheet of chromatography paper or silica plate. In the illustrated example, three pens
labelled 1, 2 and 3, and an unknown sample labeled as M are placed on a paper or plate.
The paper is suspended in a container with a shallow layer of a suitable solvent or mixture
of solvents in it. It is important that the solvent level is below the line with the spots on it.
The container is covered to make sure that the atmosphere in the beaker is saturated
with solvent vapor. Saturating the atmosphere in the beaker with vapor stops the solvent
from evaporating as it rises up the paper. As the solvent slowly travels up the paper, the
different components of the ink mixtures travel at different rates and the mixtures are
separated into different colored spots.
The diagram below shows what the plate might look like after the solvent has moved
almost to the top. In this example, the unknown sample M contained the same
components as sample 2. You can also see that sample 1 contains a mixture of two
different substances - one of which might be the same as the single compound in sample
3.
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In this experiment you will use different solvent mixtures to study the composition
of a sample and the efficiency of the separation.
Lab Reports:
 A separate formal lab report will be assigned by your instructor for this experiment.
Follow the instructions provided at the end of this experiment. You must complete the
data pages and post lab questions as part of your formal report.
Materials:
Filter paper (flat coffee filters)
Markers (at least 4 different colors, washable markers work best.)
Water
Salt
Vinegar
Sprite or any other colorless Soda
alcohol
Tape
Pencil
Jar
Saran wrap
Ruler
Transparent plastic cups
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Name: ________________________________________
Part 1: Separating a solid mixture- Simulation instructions
Data
Part 1A: separating substances from a mixture-Demonstration
Video demonstration link:
https://lonestar.yuja.com/V/Video?v=5550040&node=24376898&a=1181474347&autopl
ay=1
Watch the video and collect the data below. You may have to pause or rewind the video
to collect the data and do some calculations.
1)
What is the goal in the first part of this demonstration, according to the video?
2)
How do you think you can separate these 3 components (iron filings, salt and
sand)? Draw a scheme.
3)
What PPE (personal protective equipment) was used in this video demonstration?
What is the purpose of each?
4)
Read the tutorial information shown in the video and answer the following
questions: According to the video, what is an element?
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5)
According to the video, what are some properties of elements?
6)
Some properties of cobalt, iron and nickel are given in the video. How can you use
these properties to differentiate or identify one of these elements?
7)
According to the video, what is a compound?
8)
According to the video, what is a mixture?
9)
What is a solution, according to the video?
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10)
In your own words, what is the difference between a compound and a mixture?
Provide an example for each.
11)
From the equipment manual provided in the video write the information about the
glassware and equipment available for this lab. There are 7 instruments in that manual.
12)
From the material facts file write the information about the 3 substances you will
be separating. There are 5 facts for iron and 4 facts for each salt and sand.
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13)
What equipment from the cupboard was used to separate the iron from the
mixture? Explain how do you think this separation works.
14)
Calculation: If the initial mixture contained 5.08 g of iron and 3.26 g of iron were
collected using the magnet, what was the percent recovery for iron? Show your
calculation.
15)
Which instruments from the cupboard were used to separate the sand from the
mixture? Describe and explain how they were used for the separation.
16)
Calculation: If 11.87 grams of sand (SiO2) were contained in the mixture, how
many atoms of oxygen were in the mixture?
(Hint: you can either convert grams of SiO2 to moles, then convert moles to molecules
(using Avogadro’s number) and then relate molecules to atoms of oxygen OR you can
convert grams of SiO2 to moles, then relate to moles of oxygen and finally use Avogadro’s
number to find the atoms of oxygen)
Show your calculation.
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17)
Which equipment from the cupboard was used to separate the salt from the water
solution? Describe and explain how they were used for the separation of salt from the
water.
18)
Calculation: What is the percent composition of salt if there were 17.83 grams of
salt in a sample with a total mass of 43.67 grams? Show your calculation.
Part 1B: Identifying substances- Demonstration
Once you finish your separation demonstration you will proceed to Stage 2 where you will
have to classify substances as an element, compound or mixture. Watch the video and
collect the data below. You may have to pause or rewind the video to collect the data.
19)
According to the info in the video, how is unknown A described?
Unknown A:
20)
According to the info in the video, how is unknown B described?
Unknown B:
21)
According to the info in the video, how is unknown C described?
Unknown C:
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Review the definitions for Element, Compound and Mixture given in the video and answer
the following:
22)
Based on the description provided how would you classify unknown A: element,
compound or mixture? ______________________________
23)
Based on the description provided how would you classify unknown B, element,
compound or mixture? ____________________________
24)
Based on the description provided how would you classify unknown C, element,
compound or mixture? __________________________
25)
Observe the placement of the containers, where your predictions correct? If not,
do you understand why your prediction was incorrect?
26)
Based on the material Disposal Form provided at the end, what was the identity
of unknowns A, B and C?
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Part 2: Separation of a liquid sample by thin layer chromatography (TLC).Simulation
For the simulation go to the following website: https://elearning.cpp.edu/learningobjects/organic-chemistry/tlc/
1) Read the information provided about TLC on the right of the screen to get more
familiarized with this technique.
2) Observe the animation on the left of the screen: do you see how one spot (initial
sample) is separated into two? Does this indicate the initial spot was an element,
compound or mixture? _________________________
3) Proceed to the simulation by clicking start.
4) For the chamber on the left drag the slider all the way to the left until you see
Solvent #1: 100% hexane: 0% Ethyl acetate. This mixture of solvents is nonpolar
therefore it shouldn’t be able to drag the samples through the plate.
5) For the chamber on the right, drag the slider all the way to the right until you see
Solvent #2: 0% hexane: 100% Ethyl Acetate. This mixture of solvents is polar
therefore it should drag both samples far in the plate.
6) Click on start experiment.
7) Observe the plates. Were you able to separate the components of the sample
with either of these solvents? Explain by describing far the samples traveled in
the plate for each case.
8) Take a screenshot of this separation and place it here
9) Change the composition of the solvent mixture in both chambers and start the
experiment again. You can select any combination as long as they are different
from each other. What solvent composition did you use for each chamber?
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10) Click start experiment
11) Observe the plates. What solvent gave a better separation?
12) Take a screenshot of your chromatography and place it here.
13) How do these solvent mixture results compare to the previous results? (100%
hexane and 100% ethyl acetate).
14) Determine the Rf (retention factor) for each spot (each color) for the last two plates
(4 calculations) by using the equation:
𝑅𝑓 =
distance traveled by a component
distance traveled by the mobile phase
Rf is a ratio; it has no units and it has a value between 0 and 1. Organize all your Rf
values in one data table for ease of comparison. Each color should have an R f value.
(Show all your work) NOTE: you can use your printed paper or directly the screen and a
ruler to measure the distances the samples (dots) traveled and the distance the solvent
traveled to calculate the Rf for each dot. These are relative values so it doesn’t matter the
size of the image.
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Part 3: AT HOME
Paper chromatography can be used to separate pigments from markers that you may
have at home.
Instructions: Look at these videos before doing this lab:
https://www.youtube.com/watch?v=1LdYvgy94fg
https://youtu.be/08YMBGS1pYU
1) Cut pieces of paper approximately 8 cm by 5 cm. Write your name in PENCIL on the
top of each paper.
2)Trace a line with pencil at approximately 1 cm from the bottom of each paper
3) You will make 5 samples on each paper: Make 4 spots using the markers on the pencil
line. Each marker will be one spot, then make one spot to combine two or more markers.
Prepare enough identical samples to use with the different solvents.
4) Mix a cup of water with a teaspoon of salt, this will be your solvent #1
5) Prepare chambers by adding each solvent to the transparent cups. (Vinegar is solvent
#2, sprite will be solvent #3, alcohol (if available) will be solvent #4. If alcohol is not
available, use another clear solvent or a combination of solvents as solvent 4. Make sure
you indicate which solvents you used.
6) Place the paper in the chamber making sure the liquid is touching the paper but that
the liquid level won’t be higher than the spots. Use tape and a pencil or a stick to keep
the paper straight by suspending it on the top of the jar/cup. To avoid evaporation of the
solvent, cover the jar/chamber with wrap. Do not move the chamber once you put your
paper sample. Take a picture of your jar with the paper in the chamber.
7) Allow the liquid to climb through the paper until it is almost at the top (around 1 cm
away). This process can take hours!
This is a picture of how your system should look like:
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8) Remove paper from the chamber and allow to dry. Take a picture of the chromatograms
(the papers) once they are done. If you obtain a good separation, calculate the Rf values
and include them in your report.
9) Repeat the experiment with the other solvents (Note: You can run these
simultaneously)
10) Write a conclusion or comment about your separation of inks in the markers at the
bottom of this page.
Pictures of your experiment: (Don’t forget your name on the top of the chromatography
paper)
Conclusion: (Which solvent works best for this separation?)
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Name: ____________________________________
Classification of Matter. Separation of Mixtures
Postlab questions:
Your instructor may ask you to answer these in your lab notebook, or to answer directly
on this page and turn it in, or to include these answers in a formal lab report. Follow your
instructor’s directions.
1) A CHEM1411 student doing the separation of solid obtained the data below. The
masses on the left are the experimental masses obtained by the students after the
separation. The masses on the right are the theoretical masses that were used by
the instructor to prepare the sample.
To determine the % recovered for each component you need to calculate a ratio
between experimental mass (mass found) and the theoretical mass multiplied by 100.
Experimental mass found/theoretical mass grams x 100 = % recovered.
Based on these results,
Part 1: Separation of solids
Experimental mass of sand: ____15.359 g _________Theoretical: ___15.891 g_____
Experimental mass of iron: ____3.253 g__________ Theoretical:___3.189 g_______
Experimental mass of salt: _______16.965 g _____ Theoretical:____17.001 g_____
a) calculate the % recovery for each substance. Show your calculation.
b) Comment on the accuracy of the results from this table. (The theoretical values is what
you were expecting, the experimental value is what was actually collected after the
separation)
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2) Using the data above determine the % composition of the original sample (How
much of each substance in % mass was in the original sample, use the theoretical
values) Show all your calculation.
3) Using the data above, calculate how many moles and how many atoms of iron
(Fe) were experimentally separated from the sample. Show all your calculation.
4) Sand is basically silicon dioxide (SiO2). Determine the number of molecules that
were contained in the original sample. How many atoms of oxygen were contained
in the original sample? (Use the theoretical values) Show all your calculation.
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5) In TLC, why did the samples separate in a mixture of ethyl acetate and hexane but
didn’t separate when these solvents were used alone?
6) Is it better to have a tall plate or a short one? Why?
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