Density Lab Report

Jennifer Wilson
9/24/08
Chemistry 201-2
Mr. Schoudel

Introduction:
In science there are several questions that require experiments and tests to discover and understand the result. Our class recently discussed density, mass, and volume. All three of these components were key in solving our scientific question. Our experiment was to find the most accurate way for a vial to float into two different types of water, with different densities. The two types of waters consisted of warm fresh water and cold salt water. The water was poured into a fish tank, with blue die in the warm fresh water, displaying the two layers of water. We were given the information that the density of the warm fresh water was greater than 1.00 g/cm3 and the density of the bottom layer was less than 1.00 g/cm3. When my partner, Lucy and I first heard about this experiment, we did not know how to approach it. We went through a long process of brainstorming ideas about how to find an accurate way to approach this question. Our first thoughts were to put some type of weight in the vial to allow it to sink when placed in the water. We thought that putting boiling water or freezing water in the vial, would add weight to the vial, causing it to sink. We were not sure if this was at all accurate, which is why this experiment was so challenging for us.
In addition, it was almost like trial and error, until we observed our materials and the question, which lead us to a more accurate procedure. We were correct about putting weight in the vial, however water was maybe not the most accurate object to add weight with. We also observed the density formula; Density = Mass/Volume. This gave us the idea that we could find the density of the vial, and as a result the vial would float in the middle of the two waters. Our goal was to make the mass of the vial the same as the volume. This helped our process to become more accurate and answered several of our questions.

Hypothesis:
Our hypothesis is to place a type of weight in the vial; therefore the vial will float in the middle of the two types of water. Our initial weight was more water, however as the lab progressed, we decided that we would try to add a different weight, such as sand or table salt.

Materials:
• One large fish tank
• One small plastic vial
• Warm fresh water
• Cold salt water
• Sand
• Density Formula: Density → Mass/Volume
• Small (most accurate) graduated cylinder
• Analytical scale
• Pencil and pen to record data and results

Methods:
• Record initial mass of the vial
• Put water in graduated cylinder to determine volume (fill to 60 ml mark)
• Put water in vial (Fill to the top)
• Test the volume of the vial
• Record the mass of the vial with sand
• Test the experiment
• If it does not succeed, then keep adding or subtracting weight from the vial
• Also continue to test the weight of the vial each time, therefore your result is more accurate

Data/Results:
Test # 1 X
Total Mass: 24 grams + weight of vial = approx. 28- 30 grams
Result: Sunk to the bottom of the tank
Test # 2 X
Total Mass: 29. 457 grams
Result: Sunk to the bottom of the tank
Test # 3 X
Total Mass:
22.2 grams
Result: Float/ Remained a little above water
Test # 4 X
Total Mass: 24.28 grams
Result: The vial remained at the top of the water
Test # 5 +
Total Mass: 25.2 grams
Result: The vial remained in the middle of the two waters

Discussion/ Analysis:
Our hypothesis for this experiment was to put some type of weight in the vial; therefore the vial could float in the middle of the two types of water. This was a step in the right direction because it was important to add more weight to the vial, to successfully carry out the experiment. As the experiment progressed we noticed that adding sand to the vial would add weight and therefore would make our experiment accurate. We had a lot of difficulty discovering the correct amount of sand because we had to observe the density formula as we were adding or subtracting weight from the vial. The volume of our vial was 24 ml and we had to make the mass 24 as well because we need to balance out the density, which was 1 ml. This does not seem very difficult, however you had to remember that the vial also weighed something; therefore we had to consider this and adjust our experiment to this weight. Furthermore, each attempt to sink the vial low enough to float in the middle, was closer and closer. With out first attempt, we forgot to subtract the weight of vial, therefore making the vial too heavy and sinking right down to the bottom. On our next tries we either added to much sand or subtracted too much sand, making this a very repetitive process. Although this was quite repetitive, it made us observe every step of our experiment to make sure it was the most accurate we could make it.
In addition, one thing that could have made our experiment more accurate was taking our time with each step. I think the reason we had so many attempts was because we sometimes were so anxious and excited about testing the vial, we would remove too much weight, add too much, etc. These were key elements in having a successful experiment. Although we rushed our experiment as it became more exciting and interesting, we enjoyed each step of the process.

Conclusion:
The vial lab was a fun and interesting way to introduce the density formula. This lab was not very obvious; therefore it took all the groups time to create a valid hypothesis and experiment. My partner and I struggled in the beginning of the lab because we were both unsure at how to approach the lab. However, as we looked at our materials and information, we were able to unfold the key points that were essential to a successful experiment. Even given the density formula, it was still not an easy task. Furthermore, this lab was very frustrating, as we became closer and closer to our final answer. Each step was so close, yet so far. We either needed to at more weight or subtract weight; it was not a simple job. In addition, we were also very nervous with each step because we were sometimes unsure of the result. Finally, this was an interesting and challenging experiment, however we learned to take our time and try to be as accurate as possible.