Objectives: To become familiar with the separation of mixtures of solids.
1. Separating out the Iron
a. Use your digital scale to determine the mass of your weighing dish.
Scale is at zero before weighing. Weighing dish is weighed.
b. Empty the entire mixture of solids from the plastic bag into the weighing dish and determine the gross mass of the total mixture and weighing dish. Compute the net mass of the mixture: this is equal to the gross mass of the weighing dish with the mixture less the mass of just the weighing dish determined in 1-A.
Empty bag of mixture. Mixture is weighed on scale.
c. Spread the mixture into a very thin layer over a full sized piece of paper.
Mixture is emptied onto full sized paper and spread into a very thin layer.
d. Cut a second piece of paper into a 10-cm square. Weigh and record its mass and set it aside.
10-cm square is placed on a zero scale and weighed.
e. Wrap a small square of clear plastic over the magnet. Remove the iron powder/filings by passing the magnet closely over the surface of the entire mixture. Repeat several times to make sure you’ve collected all the iron.
Wrap a small square of clear plastic over magnet.
Removing iron powder/fillings over the surface of mixture and repeating.
f. Holding the magnet over the 10-cm square of paper, carefully remove the plastic and allow all the iron to fall onto the paper. Weigh and determine the net mass of the iron powder/filings.
Holding magnet over 10-cm paper, carefully remove plastic and weigh iron.
2. Separating out the Sand
a. Put the remaining mixture, containing sand, benzoic acid, and table salt into your beaker and add 50 mL of distilled water.
Take remaining mixture and place into beaker.
Measure out 50 ml of distilled water.
Pour 50 ml of distilled water into beaker that contains the mixtures.
b. Set up the beaker stand and burner fuel and heat the beaker of solids and water to near boiling. Stir the mixture to make sure all soluble material dissolves. At this point, the benzoic acid and the sodium chloride should have dissolved and been extracted from the insoluble sand.
Heat beaker to near boiling and stir mixture to make sure all soluble material dissolves.
c. Decant (pour) the liquid while it is hot into a small paper or Styrofoam® cup.
Pour mixture, while hot into a Styrofoam cup.
d. Pour another 10 to 15 mL of distilled water into the beaker containing the sand, bring the mixture to a boil, and decant again into the same cup used in 2-C. This assures that any remaining salt and benzoic acid is removed from the sand.
(During this process my beaker broke, but no harm was done and I was wearing proper equipment!)
Reheat beaker with another 10-15 ml of distilled water to ensure remaining salt and benzoic acid is removed from cup. (Had to use a glass from home equivalent to beaker, since beaker broke in middle of experiment.
e. Make an ice bath by placing a small amount of crushed ice and tap water into a coffee cup or similar container that is large enough to hold your paper cup of benzoic acid and salt solution. Make sure the ice bath level is higher than the solution level but low enough so that no additional water can pour into the solution cup.
Make ice bath in a coffee cup.
f. Place the cup containing the water solution of benzoic acid and salt into the ice bath. Observe the benzoic acid crystallizing out of the solution as it cools. Set this water bath assembly aside until the next section.
Place cup containing benzoic acid and salt solution into ice bath cup.
g. Heat the sand in the beaker over low heat until the sand is completely dry. Sand has a tendency to splatter if heated too rapidly. The possibility of sample loss can be reduced by covering the beaker with a small saucer and heating it very slowly. You might accomplish this also by