3: LAB 3 - SEPARATION OF SAND AND SALT
- Page ID
- 505954
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The purpose of this experiment is to
- Separation of a mixture containing an unknown composition of sand and salt.
- Calculate the percentage of sand and salt in the unknown mixture.
INTRODUCTION
Matter can be classified as a pure substance or a mixture. Pure substances include elements and compounds. Elements are the simplest forms of matter that cannot be decomposed into other types of matter. They are found in the periodic table. A compound is a chemical combination of elements. Mixtures can either be homogeneous, if they are uniform throughout, or heterogeneous, if they are non-uniform.
Mixtures can be separated by physical methods such as filtration, decantation, distillation, and evaporation. In this experiment, you will use filtration and evaporation to separate a mixture of sand and salt. Once the mixture is separated, you will be asked to determine the respective percentages of sand and salt. The following example illustrates how to perform these calculations.
Sample Problem:
A mixture of sand and salt had a mass of 3.750 g. Once separated, the mass of sand was determined to be 1.873 g. The mass of recovered salt was 1.877 g. This information determines the respective percentages of sand and salt in the mixture.
Solution
To find the percentage of a component in a mixture, we use the following formula:
\[
\text{Percentage of a component} = \left( \frac{\text{mass of component}}{\text{mass of mixture}} \right) \times 100
\]
The percentage of sand would be
\[
\text{Percentage of sand} = \left( \frac{1.873\ \text{g}}{3.750\ \text{g}} \right) \times 100 = 49.95\%
\]
And the percentage of sand would be
\[
\text{Percentage of salt} = \left( \frac{1.877\ \text{g}}{3.750\ \text{g}} \right) \times 100 = 50.05\%
\]
1) Wear chemical splash goggles throughout the experiment.
2) Gloves are provided if you wish to wear them.
3) Be careful when handling glassware while it is being heated and after it has been heated, as it will be hot. Allow all hot glassware to cool to room temperature before touching it.
4) At the end of the experiment, dispose of the sand in the "recovered sand jar" on the lab cart.
5) At the end of the experiment, wash the watch glass and evaporating dish containing the recovered salt in the sink with plenty of soap and water.
6) Be sure all glassware is clean and all equipment is returned to its proper place.
EQUIPMENT* AND CHEMICALS NEEDED
• Milligram balance
• 50.0 mL beaker
• Stirring rod
• Hot plate
• Evaporating dish
• Watch glass
• Beaker tongs
• Spatula
• Ring stand
• Ring clamp
• Wire gauze pad
• Bunsen burner
• Deionized water in the wash bottle
* Images of equipment needed in this lab can be found in the appendix (the equipment may differ or be subject to changes; follow your instructor's directions).
EXPERIMENTAL PROCEDURE
1) Using a milligram balance, weigh the following:
• an empty 50.0 mL beaker
• An empty evaporating dish with a watch glass.
2) Using a spatula, add approximately 1.00 - 2.000 g of an unknown mixture (record the mixture number or letter) to the 50 mL beaker.
3) Obtain the mass of the mixture and the beaker, and record the total mass. (Subtracting the mass of the empty beaker from the total mass will give you the mass of the mixture.)
4) Using a wash bottle, add enough deionized water to the 50 mL beaker to completely cover the mixture. Continuously stir the mixture with a stirring rod for approximately 5 minutes to dissolve the salt.
5) Decant (pour) the saltwater into the evaporating dish, keeping the sand in the 50 mL beaker.
To recover the sand, follow steps 6 through 8. To retrieve the salt, follow steps 9 through 11. Depending on the number of members in your lab group, these steps may be performed simultaneously.
6) To dry the wet sand, place the 50.0 mL beaker on a hot plate on a low setting.
Note: Once the beaker gets warm, the sand may pop. Hold the beaker with tongs and use a stirring rod to move the sand particles around it to prevent this.
7) Once the sand is completely dry and does not clump together (it will appear like sand on a beach on a hot summer day), turn off the hot plate and allow the beaker to cool. You can remove the beaker from the hot plate using beaker tongs.
8) Once the beaker is cool, obtain the mass of the 50.0 mL beaker and sand. (Subtracting the mass of the empty beaker from the combined mass of the beaker and sand will give you the mass of sand.)
9) Under the hood, set up a ring stand containing a ring clamp and wire gauze pad. Place a Bunsen burner a few inches below the wire gauze pad. (Note: Your instructor will demonstrate how to set up this apparatus. Once you set up your apparatus, be sure your instructor approves it before moving on to the next step.)
10) Place the evaporating dish on the wire gauze pad and cover it with the watch glass. Light the Bunsen burner under the wire gauze pad and heat the mixture until all the water evaporates and there is no condensation on the watch glass. Then, turn off the burner and allow the evaporating dish to cool.
11) Once the evaporating dish is cool, obtain the mass of the evaporating dish, the watch glass, and the salt. (Subtracting the mass of the empty evaporating dish and watching glass from the mass of the evaporating dish, watching glass, and salt will give you the mass of salt.)
12) Clean up all equipment, as specified in the safety precautions section.
PRE-LAB QUESTIONS
Name: ____________________________________
1) Briefly describe a procedure that can separate a mixture of sand and salt in three steps.
2) Define the following terms and provide an example of each.
Homogeneous mixture:
Heterogeneous mixture:
Element:
Compound:
3) A mixture weighing 5.000 g was shown to contain 2.445 g of sand and 2.555 g of salt. What is the percentage of sand and salt in the mixture?
4) Explain how the Law of Conservation of Matter can be applied to the previous question (Pre-lab #3).
DATA AND OBSERVATIONS
Unknown Number / Letter =
|
Mass empty a 50.0 mL Beaker |
|
|---|---|
|
Mass of the Beaker and the Mixture |
|
|
Mass of Mixture |
|
|
Mass of the Beaker and Sand |
|
|
Mass of Sand |
|
|
Mass of Empty Evaporating Dish and Watch Glass |
|
|
Mass of Evaporating Dish, Watch Glass, and Salt. |
|
|
Mass of Salt |
Percentage of Sand in the Mixture (Show Work):
Percentage of Salt in the Mixture (Show Work):
The combined Percentage of Sand and salt in the mixture (show work):
POST-LAB QUESTIONS
1) What are some potential sources of error in the experiment, and how can they be used to explain any discrepancies in the mixture's combined percentage of sand and salt?
2) Classify the following samples of matter encountered in the experiment as a homogeneous mixture, a heterogeneous mixture, an element, or a compound.
A mixture of Sand and Salt:
Sand:
Saltwater:
Salt:
Deionized water:
3) In this experiment, decantation separated the sand from the saltwater. What other method could have been used to achieve this separation?