LAB 2.4 SEPARATING A HETEROGENEOUS MIXTURE
Objective: Your lab group will obtain a mixture consisting of:
Silicon dioxide (sand)
Sodium chloride
Procedure:
Your job is to separate this mixture into its 2 components, or phases.
Discuss with your lab partners, before using any equipment, how you are going to do the separations and develop a
plan.
2. Separate the mixture into 2 separate phases. WARNING: THE ORDER IN WHICH YOU USE THESE
METHODS IS IMPORTANT!
3. Once you have separated the 2 phases, dry any that are wet gently in the oven and measure their masses.
Record the masses of each phase IN THE ORDER IN WHICH THEY WERE SEPARATED, as well as the
separation method used for each.
LAB 2.5: HOMOGENEOUS MIXTURES: USING CHROMATOGRAPHY TO IDENTIFY INKS
Objective: Use chromatography techniques to separate inks from different pens, and identify the pen used in check
forgeries.
Procedure:
1.
Cut the 2 strips of chromatography paper in half, lengthwise.
2.
With one of the black markers, place a small dot about 1.5 cm from the bottom of one of the strips of
chromatography paper. With a pencil, on the top of the paper write down the number or name of the marker used to
make the dot. Also, draw a light pencil line about 1.5 cm from the top of the paper.
3.
With the other 3 pens, place dots on the other 3 strips of chromatography paper, each about 1.5 cm from the
bottom of each strip. THERE SHOULD ONLY BE ONE DOT PER PAPER. Label each paper, in pencil, with the
number or name of the marker used to make each dot and draw a pencil line 1 cm from the top of the paper.
4.
Place NO MORE than 1 cm (in depth) of water in each of your test tubes, and place in the test tube rack.
5.
Carefully and slowly lower one of your paper strips into one of the test tubes, taking care that the ink dot is
above the water level. Fold the top of the paper over the lip of the test tube so it stays in place. Do the same for the
other 3 strips.
6.
Observe the separation of the inks. When the water has traveled to your pencil line near the top of the paper,
each strip from the water and lay on a paper towel. Carefully observe the differences among the 4 strips, noting the
resulting colors, the order in which they appear, and the length of each color band. Record in a data chart.
7.
Obtain the chromatography sample from the forged check. Compare with your suspects’ samples. Do any of
them match? If not, and time is available, obtain another pen and run another sample.
QUESTIONS:
1.
Is pen ink a heterogeneous mixture, or a solution? Explain your answer.
2.
Are the components of black ink all identical? Use evidence from your lab to support your answer.
3.
Research paper chromatography on the web. Define stationary phase and mobile phase. What was the
stationary phase and what was the mobile phase in this lab?
LAB 2.6: SOLID MIXTURES
Objective: Observe the melting points of 2 metals (an intrinsic property) and a mixture of those 2 metals.
Procedure:
1.
Place a crucible lid upside-down on top of a clay triangle arranged on a ring stand.
2.
Place a small amount of each sample of metal in the crucible lid, taking care to keep the 2 metals apart.
Make sure you know which is which!
3.
Heat the crucible lid over a blue Bunsen burner flame. Record which metal melts first.
4.
Turn off the flame, and mix the 2 melted metals together with a piece of copper wire. Then add 2 more
small samples of tin and lead to the crucible lid. You know have 3 samples: the mixture, and the 2 pure
metals.
5.
Let the mixture cool until it is solid again.
6.
Relight the Bunsen burner and heat until the samples melt, recording the melting order of each.
Questions:
1. How did the melting temperature of the mixture compare with the 2 pure samples?
2. Look up the melting points of each of the 2 metals and record.
3. Define alloy, and give some advantages of alloys over pure metals. What kind of mixture is an alloy?