2.0 Apparatuses
- 2, 50 ml beakers
- 1 ml pipette
- Pipette bulb
- Scale (+/- 0.005)
- Power source for scale
2.1 Method
1. Fill the first of the two 50ml beakers with water
2. Weigh and record the mass of the second, empty 50ml beaker
3. Using the pipette bulb, fill the 1ml pipette with exactly 1ml of water from the first beaker
4. Carefully remove the bulb and hold your finger over the top of the pipette to retain all of the water
5. Slowly wiggle your finger back and forth to release the water one drop at a time into the second beaker
6. As the water is being released, count each drop as it is released. Record the number.
7. Weigh the second beaker, with the drops of water. Record the weight.
8. Subtract the weight of the beaker from the combined weight of the beaker and the drops to determine the weight of the drops alone. Record the weight.
9. To pinpoint the weight of each drop, divide the weight of all of the drops by the number of drops. Record the weight.
10. Repeat process at least three times. Average the results.
3.0 Data collection
Weight of 50ml beaker: 27.20g
Table one. Number of drops and combined weight of drops and 50ml beaker, drops produced from 0.5ml of water by a 5ml medicine dropper.
4.0 Data processing and Presentation
1. Combined weight of drops and beaker (g) 27.74g
- Weight of beaker (g) - 27.20g
---------------------------------------------------- -----------
Weight of drops (g) 0.54g
2. Weight of drops (g) O.54g
÷ number of drops ÷ 13
------------------------ --------
Weight of each drop (g) 0.0415g
= Volume of each drop (ml) = 0.0415ml
Table two. Approximate mass and volume of a drop of water as produced from 0.5ml of water by a 5ml medicine dropper
5.0 Conclusion
Based on our experiment, I can conclude that it is possible to measure the volume of a drop of water by using a medicine dropper. Based on our result, the approximate volume of a drop of water produced by a 5ml medicine dropper is 0.0385ml. However, I believe that a more conclusive experiment to determine the volume of a drop of water would be to use many different instruments, such as a biuret, 10ml pipette and 25ml pipette. In our experiment, it is important to note that despite the best efforts to control the size of the water drops, it is very likely that the drops were varied in size; therefore, the results we achieved are only approximate. However, we were able to use the time provided, making it possible to complete five trials, making the results more conclusive. However, we would have had more conclusive results, had we completed three trials of four different instruments instead. Also, in our experiment we used a graduated cylinder to measure 0.5ml water, because the medicine dropper did not include measurement. However, the dropper could not reach the bottom of the cylinder, so we drew the 0.5ml of water from the 10ml mark to the 9.5ml mark. This type of measurement relied mostly on human observation, meaning that the amount of water used in each trial was not exactly 0.5ml, which could have impacted the results if the size of a drop is affected by the amount of water in the medicine dropper. If I were to repeat this experiment again, I would use different measurement instruments as well as find the volume of water in each instrument from mass. By determining volume from mass, one would be able to eliminate more of the possibilities for human error because a quantity determined by a scale available in our laboratory is a quantities measurement, correct to 0.005 or 0.0005 grams whereas measuring volume from a cylinder is a much less accurate method to measure quantity. Although the cylinder is one method to accurately measure volume, by using the unaided eye to remove 0.5ml of water from the cylinder, the measurement is no longer exact. Because one gram= one millilitre, the method of using mass to determine overall volume would be the method which I would use in the future. This manner of measurement would keep the experiment more controlled. Another important change I would make would be to change my research question to ascertain the approximate volume a drop of water. In order to achieve this, one would have to test many different methods of production of a drop of water, but the results would be more general and easier to apply in other situations.
5.1 Modifications
In our lab, we were unable to locate a 1ml pipette, so we replaced the pipette with a 5ml medicine dropper.
- 5ml medicine dropper replaces 1ml pipette
- 1 50ml beaker replaces 2 50ml beakers
- 1 10ml graduated cylinder is required
1. Fill the graduated cylinder with 10ml of water.
2. Weigh and record the mass of 50ml beaker.
3. Fill the medicine dropper with 0.5ml of water from the graduated cylinder (from 10ml to 9.5.ml).
4. Carefully apply pressure to the bulb of the medicine dropper to release one drop of water at a time into the beaker.
5. As the water is being released, count each drop. Record the number.
6. Weigh the beaker, with the drops of water. Record the weight.
7. Subtract the weight of the beaker from the combined weight of the beaker and the drops to determine the weight of the drops alone. Record the weight.
8. To pinpoint the weight of each drop, divide the weight of all of the drops by the number of drops. Record the weight.
9. Repeat process at least three times. Average results.
5.2 Summary Questions
- How does the volume of a drop of water compare to the volume of a drop of other liquids produced by the same instrument?
- How does the volume of liquid water drops compare to the volume of solidified (frozen) water drops?
- What would the impact be on the volume of the ice if it were frozen in a vacuum?
- Does atmospheric pressure affect the volume of a drop of water?
- How does the volume of a drop of water attained in the lab compare to the volume of a raindrop?
- How does mineral content affect volume of a drop of water?
- How varied in size are drops of water produced by the same instrument if equal force is applied?
- Does the pressure of the water in the medicine dropper affect the volume of the drops produced by the dropper?
