Lab 1: The Mysterious Matter Column PDF

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The “Mysterious Matter” Column

INTRODUCTION In this experiment, we were given three objects out of the six that had to be tested out for its density: a rubber stopper, cork stopper, and 20mL of water. Our goal was to determine which

of the three objects would float or sink, and the way to figure it out was through its density. Density is defined as the degree of compactness of a substance (The McGraw-Hill Dictionary, 2003). In order to find out the objects’ density, we must first determine its mass and volume. However, for a liquid, the mass (grams) is divided by the volume (milliliter), while for a solid, the mass (grams) is divided by its volume (cubic centimeter). If the object has a density less than 1 g/cm ❑❑3 (the density of water), it will float. However, if it has a density greater than water, it will sink. Since the density of a pure substance in its solid phase is more dense (tophat.com), my group came up with the prediction that the cork stopper will have a density less than 1 g/cm ❑3

❑

, and the rubber stopper will have the greatest density out of the three items given. For all

six of the items (rubber stopper, cork stopper, penny, a fixed volume of oil, a fixed volume of water, and a fixed volume of corn syrup) that we needed to find the density, my group predicted that the outcome from least dense to greatest dense: cork stopper, rubber stopper, fixed volume of water, fixed volume of corn syrup, fixed volume of oil, and penny. METHODS/ MATERIALS In order to determine the objects’ mass, we used an electronic balance. While for the volume, we used a graduated cylinder. Since the volume of water was already fixed, we did not need to determine its volume. One of the key materials used was the glass rod. Since the cork stopper floated in the graduated cylinder, we did not have an accurate representation of its volume. By using a glass rod to push down the cor stopper, it gave us a better representation of its actual volume. Once the object went inside the graduated cylinder, we had to subtract the initial volume with the final volume in order to find the accurate volume of the object. RESULTS

MASS (grams)

VOLUME (mL)

DENSITY (g/mL)

Rubber stopper

4.50

4.0

1.1

Cork stopper

0.51

4.5

0.11

20 mL of water

19.31

20

0.97

CONCLUSION The prediction for the three objects given to my group matched the results. The rubber stopper had the greatest density of 1.1 g/cm ❑❑3 , while the copper stopper had the least density of 0.11 g/cm ❑❑3 . This meant that the rubber stopper sunk, while the cork stopper floated. The fixed volume of water remained in the “middle.” However, the prediction of the six items from least dense to most dense was incorrect. Our prediction was that the order would be cork stopper, rubber stopper, fixed volume of water, fixed volume of corn syrup, fixed volume of oil, and penny. In reality, the results were the cork stopper, a fixed volume of oil, fixed volume of water, rubber stopper, fixed volume of corn syrup, and penny. The result showed that the cork stopper was the least dense, while the penny was the most dense. That result corresponded with our prediction. I think one possible error could be the volume of the cork stopper is not as accurate as it could have been since a glass rod was used. The pressure from the glass rod could have made the volume higher than it really was. Another error could be the electronic balance for the mass. Since the balance originally gave the mass of the rubber stopper as 4.62 grams, but when we put again on the balance, it gave us 4.50 grams.

POST-LAB QUESTIONS 1) The concept that heavy items will always sink in water, while light things will float is not always true because an object floating or sinking is determined by its density. Even if an object, like an apple, is heavier (in weight) compared to a penny, the apple will float. This is due to the fact that apple has a less density than a penny. 2) The density of a piece of pure gold is 19.3 g/mL, while the density of a piece of polypropylene plastic is 0.91 g/mL. Since any substance that has a density higher than the density of water will sink, while any density less than density will float. I can predict that

the piece of pure gold will have a greater density than the penny, therefore, it will most likely be on the bottom of the column. The piece of polypropylene plastic has a density that is less than water, but not less than the cork stopper, I can predict that it will be in the middle of the cork stopper and the fixed volume of oil in the column. 3) The length of each side of the aluminum cube is 1.4 cm. Since the mass and density was given, we only have the find the volume. The formula used to get the volume is V= mass of a substance over density (V= 16.2g/ 2.7 g/cm^3). The result would be 6 cm^3. However, we only need one length of the aluminum cube, therefore, we must find the cubic root of 6. The final answer would be 1.4 cm. 4) I think in certain solid samples, such as the crock stopper, it is more accurate to determine their volume by measuring their dimension and calculating its measurement because when displaced in water, the sample floated. This made the initial volume and density inaccurate. However, samples, such as the rubber stopper and penny, water displacement would give a more accurate volume because it would be harder to determine an accurate reading of its dimensions. 5) I think that the water displacement method will not work for calculating the density of a tablespoon of sugar because sugar dissolves when there is contact with water....