Methods of Analysis Test #1: Polarity, or Effect of a charged rod on a stream of liquid: This test was used to determine the relative polarity of the unknown liquid. The liquid was allowed to run out of a buret and a charged rod was brought up next to the stream. The observations were reported as to whether or not the stream of liquid responded to the charged rod and to what degree. Try this at home with water and a plastic spoon. Rub the plastic spoon against a sweater and move it close to a small stream of water running out of your faucet! Test #2: Volatility, or Rate of Evaporation: A thermometer probe was wrapped with a strip of filter paper. This assembly was soaked in one of the liquids for one minute. The probe was removed, and the temperature change was monitored as the liquid evaporated. The results are given in Graph 1 below. (See Graph) Graph 1: The curves generated of the change in temperature over time for the substances acetone, hydrogen monoxide, ethylene glycol, n-butanol, hexane, and toluene Test #3: Surface Tension, or Number of drops on a Penny: Drops of the unknown liquid were placed onto a penny. The number of drops was counted and recorded. This test can be an indication of the relative surface tension of a liquid. Number of drops that stayed on the penny were recorded. Test #4: Viscosity, or How fast does an object fall through the liquid: A steel ball was allowed to fall through one meter of each liquid. This test can be used determine the relative viscosity of the unknown liquid. The time was recorded as the number of seconds it takes for the ball to travel through a specified distance. Test #5: Capillary action and Polarity: A glass capillary tube was submerged into a sample of the liquid and the amount the liquid rose was determined. This test can be used to infer the extent of attraction of each liquid to glass and hence its polarity. Glass itself is polar, so the extent of attraction will indicate the polarity of the substances. The height in millimeters the liquid rose was recorded. Results Table (See Table)
Methods of Analysis
Test #1: Polarity, or Effect of a charged rod on a stream of liquid:
This test was used to determine the relative polarity of the unknown liquid. The liquid was allowed to run out of a buret and a charged rod was brought up next to the stream. The observations were reported as to whether or not the stream of liquid responded to the charged rod and to what degree.
Try this at home with water and a plastic spoon. Rub the plastic spoon against a sweater and move it close to a small stream of water running out of your faucet!
Test #2: Volatility, or Rate of Evaporation:
A thermometer probe was wrapped with a strip of filter paper. This assembly was soaked in one of the liquids for one minute. The probe was removed, and the temperature change was monitored as the liquid evaporated. The results are given in Graph 1 below. (See Graph)
Graph 1: The curves generated of the change in temperature over time for the substances acetone, hydrogen monoxide, ethylene glycol, n-butanol, hexane, and toluene
Test #3: Surface Tension, or Number of drops on a Penny:
Drops of the unknown liquid were placed onto a penny. The number of drops was counted and recorded. This test can be an indication of the relative surface tension of a liquid. Number of drops that stayed on the penny were recorded.
Test #4: Viscosity, or How fast does an object fall through the liquid:
A steel ball was allowed to fall through one meter of each liquid. This test can be used determine the relative viscosity of the unknown liquid. The time was recorded as the number of seconds it takes for the ball to travel through a specified distance.
Test #5: Capillary action and Polarity:
A glass capillary tube was submerged into a sample of the liquid and the amount the liquid rose was determined. This test can be used to infer the extent of attraction of each liquid to glass and hence its polarity. Glass itself is polar, so the extent of attraction will indicate the polarity of the substances. The height in millimeters the liquid rose was recorded.
Results Table (See Table)
Post-Investigation Analysis
Now that you have had a chance to analyze the results, in 5-8 sentences each:
- Provide an identification of each unknown, explaining why you think that is the case. Make sure to consider all the results from each test in your discussion, both in the table and the graph. Explain the role of each experiment in your identification.
- Identify the intermolecular forces present in each substance that would cause it to exhibit its specific physical properties and explain why these intermolecular forces cause these properties.
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