What two conditions are considered when determining whether a molecule is polar or non-polar?.
Pre-lab Questions
What two conditions are considered when determining whether a molecule is polar or non-polar?
What determines if a bond is polar?
List several examples of polar molecules.
List several examples of non-polar molecules.
What is the rule when using polar and non-polar solvents?
Experiment: Slime Time
Some inks are polar while others are non‐polar. A polar solvent will pick up polar inks, while a non‐polar solvent will pick up non‐polar inks. In this lab you will use inks to identify slime and silly putty as polar or non‐polar. You will also use paper chromatography to verify the inks are correctly identified as polar or non‐polar.
Procedure
**Take photographs of your experiment for Parts 1, 2, and 3; and your results. Submit them with your laboratory report.**
Part 1: Making Slime
Weigh out 0.5 g of guar gum into a 250 mL beaker.
Measure 50.0 mL of distilled water into a 100 mL graduated cylinder and pour it into the 250 mL beaker that contains the guar gum.
Rapidly stir the mixture with a stirring rod for at least 3 minutes and until the guar gum is dissolved.
Measure 4.00 mL of a 4% Borax solution into a 10 mL graduated cylinder and add it to the guar gum and water.
Stir the solution until it becomes slime. This will take a few minutes. If the slime remains too runny, add an additional 1.0 mL of the 4.0% Borax solution and continue to stir until the slime is the right consistency.
Once you are satisfied with the slime, pour it into your hands. Be sure not to drop any of it on to the floor.
Manipulate the slime in your hands. Write down observations made about how slime pours, stretches, breaks, etc.
CAUTION: Slime is slippery and if dropped it can make the work area slick.
Place the slime back into the beaker and WASH YOUR HANDS.
Part 2: Slime and Putty Ink Tests
On a piece of notebook paper make one 20-25 mm long mark of each of the inks you are testing. Space the marks at least one inch apart. Use a pencil to label each mark with its description.
Water soluble inks include those in highlighters and certain pens.
Water insoluble inks include those in permanent pens/markers, newsprint, and a dry-erase markers.
While the inks are drying, select a passage or a picture in the newspaper to test with the slime.
Break off a small piece of slime that is 3 – 5 cm in diameter. Gently place this piece on top of the newspaper print, and then carefully pick it up again.
Observe and record in Table 1 whether or not the ink was picked up onto the slime.
Break off another small piece of slime. Once the inks from Step 1 have dried, gently place the slime on top of the first spot on the notebook paper, and then carefully pick it up. Repeat this for each of the inks. Observe and record which inks were picked up (dissolved) by the slime in Table 1.
Repeat this ink testing two more times for accuracy.
Before performing ink tests on silly putty, in the Data section, hypothesize which inks the silly putty will pick up.
Perform ink tests on silly putty in the same manner as above. Record your results in Table 2
Part 3: Chromatography of Ink Samples
Use a pencil or scissors to poke a small hole in the center of a piece of filter paper (see Figure 4).
Spot the filter paper evenly spaced approximately 2 cm from the small hole with the two insoluble inks and the two soluble inks that were used in Part 2.
Obtain a ½ piece of filter paper. Fold the paper in half several times so that it makes a narrow wick.
Insert the wick into the hole of the spotted paper so that it is above the top of the filter paper by approximately 2 cm.
Fill a 250 mL beaker 3/4 full with water.
Set the filter paper on top of the beaker so that the bottom of the wick is in the water. The paper should hang over the edge of the beaker with the spotted side up.
Allow water to travel until it is approximately 1 cm from the edge of the filter paper. Remove the filter paper from the beaker.
Observe which inks moved from where they were originally spotted. Record your observations in Part 3 of the Data section.
What two conditions are considered when determining whether a molecule is polar or non-polar?
