Penny Lab. To determine how the age of a penny affects the number of drops of water a penny will hold.

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Chastity Davidson
5 years ago
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1 Introduction: AIM: Prediction: Over the years the mass of a penny has changed quite a bit. The first penny with President Lincoln on it was made in Earlier pennies were made of pure copper from 1793 to Pennies have also been made of bronze. In 1943, the content of the penny was changed to zinc coated steel because there was a copper shortage during World War II. Before 1982, pennies were 95% copper and 5% zinc. After 1982, the composition was 97.6% zinc and 2.4% copper 1. Since pennies have been changed in mass over the years due changes in how pennies are made, I think it would be interesting to see if the age of the penny will affect the number of drops of water the penny will hold. To determine how the age of a penny affects the number of drops of water a penny will hold. I think older pennies will hold more drops than newer pennies. HYPOTHESIS: IF we decrease the age of the penny (independent) THEN we will increase the number of drops of water (dependent) the penny will hold. Reasoning: Older pennies are made of different metals than newer pennies, so this difference may affect the way the penny interacts with water. 1 Glenn Elert, Mass of a Penny, < (3 September 2007). John Smith Page 1 29/10/2014

2 VARIABLES: Independent The age of the penny Dependent The number of drops a penny will hold Controlled - (see list below) The same side of the penny The same rate of drops The same size of drops The same water source The same eyedropper The same height of eyedropper Unable to Control - (see list below) The cleanliness of the pennies, because some pennies looked like they might be dirtier than others. The table vibrations, because other groups were bumping the table at different times during our experiment. The person using the eyedropper, because we took turns dropping the water on the pennies. The temperature of the water may have increased as we held the eyedropper for longer periods of time. MATERIALS: 1 Eyedropper bottle with water 1 Pre 1982 penny 1 Post 1982 penny Paper towels SETUP: Pre 1982 Penny Post 1982 Penny John Smith Page 2 29/10/2014

3 METHOD: 1. Fill the eyedropper bottle from the tap in the lab sink. 2. Rinse a penny dated 1980 and a penny dated 1984 in tap water and dry completely with a paper towel. 3. Place the 1980 penny on a dry paper towel with its head side up. 4. Hold the eyedropper exactly 10 cm about the penny. Then start dropping the same size drops of water on the penny with the eyedropper at a constant rate of one drop per second. 5. Refill the eyedropper from the same eyedropper bottle if necessary. 6. Count each drop until the bubble of water runs over the edge of the penny. 7. Record the number of drops for that trial in the table. 8. Dry off the penny. 9. Repeat steps 3 8 ten times. 10. Place the 1984 penny on a dry paper towel with its head side up. 11. Hold the eyedropper exactly 10 cm about the penny. Then start dropping the same size drops of water on the penny with the eyedropper at a constant rate of one drop per second. 12. Refill the eyedropper from the same eyedropper bottle if necessary. 13. Count each drop until the bubble of water runs over the edge of the penny. 14. Record the number of drops for that trial in the table. 15. Dry off the penny. 16. Repeat steps ten times. Results: Table 1: The Affect of Penny Age on the Average of Water it will Hold Trail # Year 1980 Year Average Average = Sum of all Trials/Number of trials 1980 Average = 238/10 = 23.8 drops 1984 Average = 245/10 = 24.5 drops John Smith Page 3 29/10/2014

4 Results: (continued) The Affect of Penny Age on the of Water It Will Hold Trial # Year 1980 Year 1984 The Affect of Penny Age on the Average of Water It Will Hold Year 1980 Year 1984 John Smith Page 4 29/10/2014

5 Discussion: In general both the 1980 and 1984 pennies seem to hold similar numbers of drops of water. Both 1980 and 1984 pennies held a maximum of 27 drops of water. The 1984 penny held a minimum of 21 drops while the 1980 penny held a minimum of 22 drops. When we look at the average number of drops each held we can see that on average the 1984 penny held 0.7 more drops of water than did the 1980 penny. During most of the trials the 1980 penny seemed to hold less drops of water except for trials 4 and 5. A possible reason for this is that we changed persons handling the eyedropper during trials 4 and 5. Another possible reason could be that one of the other teams bumped into our table a couple times during these trials. There were also a couple other limitations and experimental errors during our experiment. One possible problem was that some pennies looked like they might be dirtier than others even after washing them. Depending on the types of substances on the pennies this could have affected our results. For example, soap residue will reduce the number of drops the penny will hold while oils may increase the number of drops the penny will hold. The fact that we took turns using the eyedropper may have caused us to change the rate or height of the eyedropper slightly. Dropping the drops too fast or too high may have decreased the number of drops it may hold. In general, my data is fairly reliable. Although we did have some limitations and experimental errors, these do not seem great enough to have affected the data in a large manner. Conclusion: My hypothesis was that if we decrease the age of the penny then we will increase the number of drops of water the penny will hold. Although the data is very similar for both ages of pennies, slightly more drops of water can be held on the younger penny. This seems to disprove my hypothesis. If I were to do this experiment again I would suggest making a number of improvements. One improvement I would suggest is having only one person handling the eyedropper. This may help us be more consistent with our water dropping technique and make our results more reliable. I would also suggest cleaning and rinsing the pennies very well to remove all soap and dirt from the pennies. By removing these substances we will be able to have a fairer test of the ages of pennies. It may also be helpful to remind other groups not to bump into our table while we are conducting our experiment. This may help reduce vibrations that may have caused the water bubble to burst too soon. Having completed this experiment I think it would be interesting to see how much affect the height of the eyedropper has on the number of drops of water a penny will hold. This would be interesting to know since our eyedropper likely moved a few millimetres with each trial. John Smith Page 5 29/10/2014

Relationship between Mint Date of Pennies and Density

10/18/10 Relationship between Mint Date of Pennies and Density Question: What is the relationship between the mint date of pennies and their densities? Hypothesis: There is an increasing linear relationship