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Lab Report

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José Armando Miranda

on 20 September 2012

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Transcript of Lab Report

Instituto Cristiano Bilingüe Sunshine Grade: 10th Jose A. Miranda Lab Report ''Significant Digits in Measurements'' Chemistry Class September 19th, 2012 Mr. Jose Popoff Introduction Significant Digits in Measurements No measured quantity can ever be exact; there will always be some uncertainty associated with it. The degree of certainty in a measurement is reflected in the number of significant digits contained in it. The significant digits in a measurement contain all the certain digits-those of which we can be sure-and one uncertain digit. In this report I will talk about how my team and I performed several things to learn about significant digits in measurements. I will also talk about how we measured several coins of different years but of same size and value. We measured thickness, lenght, width and the mass of the coins. Finally we measured the volume of a test tube into a beaker. Objectives The objectives of this lab activity were the followings: Learn about uncertainties in measurement. Express measurements using the proper number of significant digits. Use significant digits properly in calculations. Become familiar with common laboratory measuring instruments for length, mass, and volume. The materials we used were the followings: Materials Balance Calculator Graduated cylinder of 100 mL Metric plastic ruler Coins Test tube 1) We measured the thickness of a Honduran coin of 10 cents, we laid the ruler over the edge of the coin that we were holding in our fingers. We measured the coin in centimeters and millimeters or tenth of a centimeter.
NOTE: Each of our group member measured the coins by themselves. Procedure 2) We repeated step one but with 4, 7 and 10 coins. We observed while measuring the coins that the thickness of the coins changed. 3) We carefully measured the length and width of our chemistry book in units of centimeters.
NOTE: Each member did this step by themselves and at their houses. 4) We individually find the masses of 5 of our coins. For this step we used coins from different years, some newer and some older.
NOTE: For this step we ask to Mr. Popoff if he could help us calibrating the balance. 5) The last step pf this lab activity was when we filled a test tube to the brim with water and we carefully transfer all of it into our graduated cylinder. Each of our group member estimated the volume of water in the graduated cylinder. We repeated this step two more times with the same test tube and graduated cylinder. RESULTS Our results of the previous steps as a group were the followings: 1) Length of book Width of book 25.4 cm 20.3 cm 25.45 cm 20.33 cm Nearest hundredth Nearest tenth Number of Coins Thickness 1 coin 4 coins 7 coins 10 coins .11 cm .62 cm 1.11 cm 1.54 cm 2) Mass of coin Year of coin 6.22 g 6.25 g 6.55 g 2006 2001 2007 6.34 g 2004 3) Volume of water 20.1 mL 19.2 mL 20.0 mL 4) 1. Calculate the average thickness of one penny for each set of pennies, using significant digits properly. DATA ANALYSIS Numbers of coins Average thickness 1 coin 4 coins 7 coins 10 coins .11 cm .15 cm .16 cm .16 cm 2. Which of these numbers is the most representative value for the average thickness of a coin? Explain. Answer= I think that .16 because we have two time the same digits. 3. Calculate the area of your chemistry book; then calculate its perimeter.Record both the unrounded value and value with the proper of significant digits. Area,using nearest tenth Area,using nearest hundredth Perimeter,using nearest tenth Perimeter,using nearest hundredth Unrounded Using proper significant digits 515.62 cm 2 517.398 cm 2 515.6 cm 2 517.40 cm 2 91.40 cm 91.560 cm 91.4 cm 91.56 cm 4. Which set of calculated quantities is closer to the actual or exact area and perimeter-those using nearest tenth of centimeter or those using the nearest hundredth? Explain. Answer= I think that to the nearest hundredth because it's more exact the area and perimeter. 5. In what decimal place was there uncertainty in the mass of the coins? Answers= In the hundredth place. 6. Do you noticed any difference in the mass of a coin relative to the year it was minted? If so, what was it? Answer= Yes, in our group one coin more recently that was from 2007 had more mass, than the other coins from different years. 7. Calculate the average mass of a coin, expressing it with the proper number of significant digits.Is it possible for your average to be significantly different from that obtained by another group in your class? Explain. Average mass of a coin: 6.34 g Answer= Yes, it could be possible because we did this activity by groups and each group may have changed something else when they were calculating the average mass. 8. Calculate the average volume of water contained in your test tube.
Average volume: 19.8 mL 9. In what decimal place is the uncertainty (precision) in your measurement of the water? Answer= In the tenths place. 10. Do you think the average of three trials gives a more reliable(more accurate) value for the volume of the test tube than a single measurement?. Why or why not? Answer= Yes, because we could compare the measurements given and the volume can change because measurements can't be exact. CONCLUSIONS A measurement never can't be exact.
It's important to know how to use properly significant digits in measurements.
In the hundredth place it's difficult estimate significant digits when we refer to mass, and in the tenth when we refer to volume.
Nearest Hundredth place is closer to the exact area and/or perimeter. BIBLIOGRAPHY Google.com/images Worksheet 3A ''Significant Digits in Measurements''
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