Chemistry Honors Lab: Evaporation and Intermolecular Attractions

Lab: Evaporation and Intermolecular Attractions

2) Explain the differences in the difference in temperature of these substances as they evaporated.  Explain your results in terms of intermolecular forces.

The five substances we tested were: Methanol, Ethanol, n-Butanol, Glycerin, and Water.  All of these substances have their strongest intermolecular force being hydrogen bonding.  Of the five, though, Methanol changed the most in terms of temperature, going down a total of 14 degrees Celsius.  We believe that this major change of temperature is due to the high volatility this substance has.  This is caused by the fact that the molecule has only one potential hydrogen bond to form with another molecule.  The one site where potential hydrogen bonds can form is relatively low if compared to other the other substances.  The next largest drop in temperature was Ethanol which 6.3 degrees Celsius.  Ethanol, similarly to methanol, only has one site for a possible hydrogen bond to form with a similar molecule.  The reason why there is a 7.7 degrees difference between the two is due to the increase of the molar mass.  Ethanol has a molar mass of 45.04 grams and methanol has a molar mass of 32.04 grams.  The molar mass of ethanol means that the molecules themselves are heavier, and therefore require more energy to change its state of matter, leading to less molecules evaporating.  The change in temperature for water was -4.3 degrees Celsius.  Water, having two sites for potential hydrogen bonds to form with other molecules definitely has something to do with the 2 degrees difference in change when comparing water to ethanol.  The next substance is n-Butanol, with a change of -2.0 degrees Celsius.  n-Butanol, having only one site for possible hydrogen bonding, would commonly be thought to have a higher change in temperature, but this is not the case.  My partner and I believe it is due to the huge molar mass when compared to water; n-Butanol with 74.04 grams and water with 18.01 grams.  Finally, the last substance tested was glycerin.  The change in temperature recorded was not what was expected.  The change was +1.6 degrees Celsius.  After this result, my group can upon the conclusion that since glycerin has three sites for possible hydrogen bonding and has a substantial molar mass of 92, that the cooler temp. inside the beaker and the warmer temp. in the lab over came the evaporation cooling effect.  This was most likely due to the lack of said evaporation.

3) Explain the difference in evaporation of any two compounds that have similar molar masses.  Explain your results in terms of intermolecular forces.  

Methanol and ethanol have the two closest molar masses in the experiment with a difference of 13 grams, but there difference in temperature was among the largest being 7.7 degrees.  Even though both substances only have one site for hydrogen bonding to take place, the extra carbon atom and two hydrogen atoms where enough to alter the results.  This is most likely due to the idea of London Dispersion Forces.  The extra carbon and hydrogen atoms bring electrons with them as well.  The more electrons in a molecule, the more of a possibility that a slight change in distribution could occur.  The change in distribution could have effect on the overall polarity of the molecule and this has a ripple effect throughout the substance.  The increase in the chance for an intermolecular force to occur causes the evaporation rate to decrease because the substance with more intermolecular force requires more energy to change its state of mater.

4) Explain how the number of -OH groups in the substances tested affects the ability of the tested compounds to evaporate.  Explain your results in terms of intermolecular forces.  

The more -OH groups in the substance, the less it will evaporate.  This is due to the fact that hydrogen bonds are difficult to break.  The more -OH groups there are, the more potential hydrogen bonds there are for that substance.  With these two things in mind, one can come to the conclusion that the more -OH groups there are, the more hydrogen bonds can form, which means that there has to be more energy to change its state of matter, meaning it is less likely to evaporate.  

Chemistry Honors Lab: Electron Configuration Battleship

Lab: Electron Configuration Battleship

This "lab" was a game of Battleship but instead of placing your ships on a grid, you place them on the periodic table and instead of calling coordinates for your opponent to find, you would call out the elements using electron configuration notation.  The biggest struggle I encountered while playing was accurately communicating with my opponent.  The game's purpose was to practice using this newly learned skill, but it was still annoying at times.  I learned, through this game, that in chemistry, there are many different ways to communicate similar things.  Some methods might share more insight on specific details on certain topics, but these ways all can signify a certain element.

Picture of Battleship Set Up

Chemistry Honors Lab: Flame Test

Lab: Flame Test

In this lab, my group and I burned wooden sticks that soaked up many chlorine compounds over a bunsen burner.  Different chlorine compounds produced different shades of light.  We were to compare the results of the known compounds with two unknown substances and predict what they were.  My group decided, that since Unknown #1 had a red shade that the substance we strontium chloride.  We also determined that since Unknown #2 had a light lavender shade that the substance was potassium chloride.  Below are the answer to the pre-lab questions.

1) What is the difference between ground state and an excited state?

The ground state is when the electron configuration of an atom/element are in it's most stable and lowest energy state.  The excited state, on the other hand, is when the electron configuration is unstable and electrons are higher in terms of energy and will eventually calm down and return to the ground state.

2) What does the word "emit" mean?

Emit means that something, whether it be a photon or any amount of energy, is being created and dispersed away from it's source.

3) In this experiment, where are the atoms getting their excess energy from?

In this case, the "excess energy" is coming from the flame created by the bunsen burner.

4) Why do different atoms emit different colors of light?

Electrons, when heated, jump up to higher energy levels, but they don't stay there for long.  When they fall back down, they release their energy as photons.  For every element, the "quantized" amount of energy to go from one level of energy to the next is different.  That amount of energy determines the color of the light emitted.

5) Why is it necessary for each station to have separate wooden splints for each individual flame test?

After using on splint, the wood would be "contaminated" with that solution.  If we were to try and resoak that splint, the results of the following test would be skewed.  The reason being is that we wouldn't know which element is reacting.

Flame produced by Copper Chloride (CuCl₂)

Chemistry Honors Lab: Mole-Mass Relationships Lab

Lab: Moles-Mass Relationships Lab

The purpose of this lab was to test my capabilities of precision in the lab and to also exercise my newly acquired skills in stoichiometry.  Below are pictures of data the my group and I gathered.  That data is also used to answer questions that are located in the pictures as well.  The most likely reason why my group and I didn't get the full 100% yield of salt is that while dripping water down the watch glass to clean the solution that had gathered underneath, we probably missed some water-salt solution which lead to a decrease in the mass of the product, NaCl.

Chemistry Honors Lab: Composition of a Copper Sulfate Hydrate

Lab: Composition of a Copper Sulfate Hydrate

Copper Sulfate Prior to Heating:

Copper Sulfate After Heating:

Amount of Hydrate Used:

46.09 g (Mass of Dish + Hydrate) - 45.21 g (Mass of Dish) = 0.88 g (Copper Sulfate Hydrate)

Amount of Water Lost:

45.67 g - 45.21 g = .46 g CuSO₄ (Copper Sulfate Anhydrate)

0.88 g (Copper Sulfate Hydrate) - 0.46 g (Copper Sulfate Anhydrate) = 0.42 g (Water)

Percentage of Water in Hydrate:

0.42 g (Water) / 0.88 g (Copper Sulfate Hydrate) * 100 = 48% (Water)

Percent of Error:
(Actual percentage of water in CuSO_4 Hydrate: 36%)

((0.48 - 0.36) / 0.36) * 100 = 33% of Error



Predicted Empirical Formula:

a) Moles of Water Evaporated:

0.42 g (Water) * (1 mole / 18.01 g (Water)) = 0.023 mol (Water Evaporated)

b) Moles of Copper Sulfate Anhydrate Remaining:

0.46 g (Copper Sulfate Anhydrate) * (1 mole / 159.6 g (Copper Sulfate Anhydrate) = 0.0029 mol (Copper Sulfate Anhydrate

c) Ratio of Copper Sulfate to Water:

0.0029 g / 0.023 g = 1 (Copper Sulfate) : 8 (Water)

d) Empirical Formula:

1 CuSO₄ * 8 H₂O


Due to my percent of error being significantly higher than anticipated, I believe that my prediction of 8 water molecules for every CuSO₄ molecule is way to high.  After doing the math (see below), I have determined that, in actuality, there are supposed to be 5 water molecules for every CuSO₄ molecule.

Math to prove above statement:

Step 1) Percent to Grams

36% = 36 grams of water
64% = 64 grams of Copper Sulfate

Step 2) Grams to Moles

36 g * (1 mole / 18.01 g (water)) = approx 2 moles

64 g * (1 mole / 159.6 g (CuSO₄)) = approx. 0.4 moles

Step 3) Divide by Smallest

2 moles of water / 0.4 = 5 moles of water
0.4 moles of copper sulfate / 0.4 moles = 1 mole of copper sulfate

5 water molecules for every 1 copper sulfate molecule

Correct empirical formula for the hydrate: 1 CuSO₄ * 5 H₂O

Chemistry Honors Lab: Mole Baggie Lab

Lab: Mole Baggie Lab

This lab's purpose was to determine what substance was in a bag given minimal information.  The information given was either "A": The mass of the bag and the number of moles of the substance in the bag, or "B": The mass of the bag and the number of particles of the substance in the bag.  For my first go at this activity, I received Bag A5 and the substance inside was Zinc Oxide, ZnO.  After my first and only attempt at Set A, I received Bag B3 and inside was Potassium Sulfate, K₂SO₄.  Once finding and calculating data, we were given five substances to compare our results to.

Determining the substaces was not too difficult.  For Set A, I massed the bag and the substance (4.71 g) and subtracted the mass of the bag itself (2.56 g).  Then I used the mass of the substance (2.15 g) and divided that by the number of moles in the given sample.  The final conclusion for Set A was that the substance had a molar mass of 86 g and this value was closest with Zinc oxide having a molar mass of 81.39 g.  For Set B, I massed the bag and the substance (5.99) and subtracted the mass of the bag itself(2.55 g).  Then, I converted the amount of particles of the substance (1.20 x 10^22) to the amount of moles in the bag (0.020 moles).  Then, we took the amount of grams of the sample (3.44 g) and divided it by the amount of moles of the sample (0.020 moles) and found that the substance had a molar mass of 172 g.  This was closest to Potassium sulfate having a molar mass of 174.3 g.

Sample of Potassium Sulfate

Chemistry Honors Lab: Double Replacement Reaction Lab

Lab: Double Replacement Reaction Lab

This lab's purpose was to test my capabilities in predicting products from double replacement reactions and to get my hands on some actual chemical reactions for the first time this year.  The following will be pictures of the ten experiments, six of which reacted.  Hoping for some more chemical reactions, hopefully some explosions.....

Chemistry Honors Lab: Nomenclature Puzzle

Lab: Nomenclature Puzzle

The goal of this activity was to work with a partner and solve a puzzle.  The way this puzzle was solved was by matching the name of a compound and the formula that corresponds with it.  The biggest challenge involved in this challenge was the last five minutes.  The reason being is that when And (my partner) and I were looking for matches, it was difficult to determine whether or not those matches were in the two big chunks or left in the "straggler" pile.  My biggest contribution to this activity was my near constant communication.  Knowing what the other person has and letting him/her what your plan is allows both people to work together more efficiently and expedites the process.

Chemistry Honors Lab: Atomic Mass of Candium

Lab: Atomic Mass of Candium

The purpose of this lab was to test if the experimenters knew how to find and use data to find average atomic masses.  For Candium, my partner and I found that it has an average atomic mass of 1.28 amu.

1. Another group found that Candium had an average atomic mass of 1.25 amu.  This difference is most likely due to the possibility of them having a different sample then my group.

2. If sample sizes or were larger, I believe that the percent of error between groups would diminish due to having more atoms to analyze and therefor have a much more legitimate average than a smaller sample size would.

3. Almost any atom of Candium that had be massed would not equal the average.  The average found, in this case, was not the value of any of the three isotopes: normal, peanut, or pretzel.

4. Cy (Candy-Yum)

Chemistry Honors Lab: Chromatography

Lab: Chromatography

1. The water would not have evenly distributed from the starting point, the center, if it were not for the "wick" to transfer the water to the disk-like filter.

2. The pattern of colors produced on the filter paper could have differed due to the difference in the solubility of the ink used, the company who produced the marker/ink, and the type of marker produced.

3. Black ink is composed of many different colors of ink.  Thanks to the solubility and molecule size of those different inks and the chromatography paper, we can see each ink clearly after the process is complete.

4. The compounds that are used to make blue could differ, but due to the way this experiment was performed, I could not determine whether the compounds were the same or different.  Pigments that were in many of the pens/markers that were tested included blue, a purple-ish pink, and yellow.

5. Only water-soluble pens/markers were used due to the fact that the liquid used to carry out the chromatography process was water.  If this experiment were to test the ink in permanent markers, one could use a stronger liquid, such as alcohol.

Chemistry Honors Lab: Aluminum Foil Lab

Aluminum Foil Lab Part: Determining the Thickness

This lab was pretty straight forward.  We started the lab with the given density of aluminum, a meter

stick, a rectangular piece of aluminum, and a balance.  After obtaining these materials, we massed the

 aluminum.  Then, we calculated the volume, using mass (0.59 g) and density (2.7 g/cm^3).  Then 

after finding that value, we set volume equal to length (12.08) x width (11.90) x height (not found). 

 Then, dividing .22 mL (volume) by the length and width, we arrived at the height/thickness value, 

0.015 mm.

Chemistry Honors Lab: Density Block

Lab: Density Block

This lab was to determine the mass of a plastic block using its density and volume.  Density is mass divided volume, and volume is length x width x height.  I did this by measuring the dimensions of the block, and using these measurements to find volume of the block.  With some further calculations, I ended with a final mass of 15 grams.  

This lab was very quite simple.  My group used: the block, the meter stick, the balance, the given density, and a calculator.  With these materials we measured the the block with the meter stick.  Using the measurements of 2.52, 2.47, and 2.45, we concluded that the volume in 15.2 g/cm^3.  Then, by multiplying 0.96 g/cm^3 (the given density) and 15.2 g/cm^3, we found that the mathematical mass is 14.592.  But due to significant figures and the rules that go along with the concept, we determined that our answer would be 15 g.  After this, we massed the block using the balance, and found that the actual mass was 15.7 g.

The percent of error from our findings to the actual mass was 4.6%.  This met the requirement of <5% of error.

My group fulfilled the purpose of the "Density Block Lab" by meeting the <5% of error.  Our prior attempt was not so great.  Going through the same process as our successful trial, we had a 13% error.  This means that the perosn who is measuring should have a good handle on the measuring and "guesstimating" process used to determine the final digit in the measurement.  This lab taught me a lot about of precision has a massive role in higher level lab work.  This experience has changed my view of lab work and I can't wait to go at it again tomorrow.