Lab: What makes a mixture?
Name
Please follow the laboratory notebook format to properly record all results from this lab.
Pre Lab terms to know…
Matter
Pure Substance
Mixture
Physical property
Solution
Phase
Purpose: To describe and classify different types of mixtures and to explain how to separate them.
Use small, labeled test tubes to obtain samples of A – F. Observe the contents of each test tube. Follow
directions for each of the procedures and record your own summary of each procedure along with
observations and analysis in your lab notebook.
Test tube A
 Observe and describe the contents.
 Hold a magnet to the OUTSIDE of the tube and describe the effect.
Test tube A
Initial Observations
Effect of the magnet
Analysis
1. Are the contents of test tube A considered to be a mixture? How do you know?
2. If it is a mixture, how could you separate the parts from each other?
Test tube B
 Observe and describe the contents.
 Use a plastic pipette to carefully place two drops of the liquid into a separate tiny test tube.
 Use test tube tongs to hold the tiny test tube over a flame until the liquid evaporates.
 Observe the bottom/sides of the tiny test tube and record what you see.
Test tube B
Initial Observations
Observations after evaporation
Analysis
1. How do these results prove that the contents of test tube B are a mixture? Be specific.
2. If water is the part that evaporated, what might the other part be?
Test tube C and Test tube D
 Observe and describe the contents of each.
 For tube C, transfer a small amount of the solid into a tiny test tube, add ~1cm of water and gently
shake.
 Use a plastic pipette to carefully place two drops of the liquid part into a different tiny test tube.
 Use test tube tongs to hold this new tiny test tube (containing just the liquid) over a flame until the
liquid evaporates.
 Observe the bottom/sides of the tiny test tube and record what you see.
 Repeat for tube D
Test tube C
Initial Observations
Observations after evaporation
Analysis
1. Are the contents of test tube C a mixture? Explain using evidence from your data.
Test tube D
Initial Observations
Observations after evaporation
Analysis
1. Are the contents of test tube D a mixture? Explain using evidence from your data.
Test tube E
 Observe and describe the contents.
 Shake the tube for two seconds and observe and describe what you see.
 Allow the contents to “settle” for about one minute. Observe and describe what you see.
Test tube E
Initial observations
After shaking
Analysis
1. Describe a possible method for separating the parts of this mixture.
2. What properties allow you to separate the two parts easily? Explain.
After settling
Test tube F
 Observe and describe the contents.
 Take a very small amount of the contents and place them in a tiny test tube.
 Add water until the tube is ½ filled. Heat the water slightly over a flame for a few seconds at a
time while swirling the contents. Observe and describe what changes you see.
Test tube F
Initial observations
Observations in water
Analysis
1. Is this a mixture or a pure substance? How do you know?
Challenge
Clean up your area and return the mixtures to the teacher. Obtain an unknown mixture (mixture will have
three substances) from your teacher. Separate the mixture into its parts and give the percent mass of
each substance in the mixture. Be sure to write all steps used in your lab notebook.
Conclusion
It is easy to classify samples as mixtures, compounds, or elements when you are looking at a picture
representation of the particles that make it up. It is not as easy when you are looking at the actual
substance. Summarize the types of mixtures you observed today (could you tell they were mixtures just by
looking at them?) and discuss the techniques you can use to help you determine whether the sample is a
pure substance or a mixture.
Lab: What makes a mixture?
TEACHER DIRECTIONS:
Give one set of mixtures to each lab group.
If you do not have enough containers for this, then have 2 sets of each sample in the
front of the room…one for each side of the room…and have the students take one at a
time. Tell students to label 6 small test tubes A-F. Divide the test tubes among the
students in the group and have each obtain a SMALL sample for the test tubes.
They should have 5 additional small test tubes for testing of the samples.
SAFETY:
Do not heat the bottom of the test tubes! Slowly wave the tube over the flame to heat
it GENTLY!
TEST TUBE CONTENTS:
A = iron filings and aluminum
B = salt water
C = sand
D = sand and salt
E = oil and water
F = tea leaves
Unknown mixture is iron, salt, and sand. The identity can be given to students for a
slightly easier challenge, or not given to students for a slightly more difficult challenge.