Measurement and Uncertainty Lab Pre Lab Assessment with Answers

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Barstow Community College *

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Chemistry

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Jan 9, 2024

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Measurement and Uncertainty Lab Pre Lab Assessment Introduction Directions: Complete this pre-lab assessment to continue to the rest of the investigation. You will need a score of 100% to pass the assessment. This assessment can be attempted as many times as necessary to achieve a passing score. You may return to the pre-lab sections to study before each attempt.For each question, select your response and then click Submit to see how you did. Click Next to continue to the next question. A final results page will appear upon completion of this assessment with your overall performance. Start Question 1 How many significant figures are in the number 0.08546000? 5 7 CORRECT 4 3 9 Submit Question 2 An object known to be 20 mm in length is measured as 18 mm in length. What is the percent error? 10% , Unselected, 10% (CORRECT) 2% , Unselected, 2% 8% , Unselected, 8% 5% , Unselected, 5% 1% , Unselected, 1% To calculate percent error, you can use the formula: \[ \text{Percent Error} = \left| \frac{\text{Measured Value} - \text{True Value}}{\text{True Value}} \right| \times 100\] In this case:

\[ \text{Percent Error} = \left| \frac{18 \, \text{mm} - 20 \, \text{mm}}{20 \, \text{mm}} \right| \times 100\] \[ \text{Percent Error} = \left| \frac{-2}{20} \right| \times 100 = 0.1 \times 100 = 10\% \] Therefore, the correct option is: \[ 10\% \] Question 3 Which of the following refers to how close data are to their actual values? significance, Unselected, significance accuracy, Unselected, accuracy (CORRECT) uncertainty , Unselected, uncertainty error , Unselected, error precision, Unselected, precision Submit Question 4 Which of the following best describes an object of known mass that can be used to establish uncertainty in measurements made with a balance? trial value Standard (CORRECT) deviation

variation Question 5 Charlie is a chemistry student conducting an experiment at home, as approved by his professor. Despite attempts to eliminate sources of experimental error from his design, Charlie still finds his results have measurable uncertainty. Which of the following statements from Charlie’s professor best explains the results? There is no way to eliminate all uncertainty. , Unselected, There is no way to eliminate all uncertainty. (CORRECT) The only way to eliminate all uncertainty is to use the best equipment possible. , Unselected, The only way to eliminate all uncertainty is to use the best equipment possible. Uncertainty can be eliminated if you have a lab partner replicate the results., Unselected, Uncertainty can be eliminated if you have a lab partner replicate the results. The only way to eliminate uncertainty is to perform experiments in a formal lab setting., Unselected, The only way to eliminate uncertainty is to perform experiments in a formal lab setting. Uncertainty can be eliminated if all the equipment is properly cleaned., Unselected, Uncertainty can be eliminated if all the equipment is properly cleaned. The statement that best explains Charlie's results is: "There is no way to eliminate all uncertainty." Uncertainty is inherent in measurements, and while efforts can be made to minimize it, complete elimination is often not possible. Question 6 The mass of a wooden block is reported to be 5.20 g ± 0.05 g. What does the “0.05 g” indicate about the measurement? the confidence interval , Unselected, the confidence interval (CORRECT) the number of significant figures , Unselected, the number of significant figures random error , Unselected, random error the average , Unselected, the average the percent error , Unselected, the percent error

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The "0.05 g" in the mass of the wooden block, reported as 5.20 g ± 0.05 g, indicates the uncertainty or margin of error in the measurement. It represents the precision of the measurement and suggests that the actual mass is likely to fall within the range of 5.15 g to 5.25 g. Therefore, the correct option is: "random error" I apologize for the confusion. The "0.05 g" in the mass of the wooden block, reported as 5.20 g ± 0.05 g, indicates the uncertainty or margin of error in the measurement. It is related to the precision of the measurement, but more specifically, it is associated with the confidence interval. Therefore, the correct option is: "the confidence interval" Question 7 Which of the following statements about significant figures is correct? Trailing zeroes in a number containing a decimal point are insignificant., Unselected, Trailing zeroes in a number containing a decimal point are insignificant. They are digits that describe the accuracy of measurement., Unselected, They are digits that describe the accuracy of measurement. (CORRECT) All digits are considered significant., Unselected, All digits are considered significant. The number of significant figures in a measurement is determined experimentally., Unselected, The number of significant figures in a measurement is determined experimentally. Leading zeroes are significant., Unselected, Leading zeroes are significant. The correct statement about significant figures is: "The number of significant figures in a measurement is determined experimentally." Significant figures are determined based on the precision of the measurement, and they reflect the reliability of the recorded digits.

I apologize for the confusion. Let me clarify: The correct statement about significant figures is: "Trailing zeroes in a number containing a decimal point are insignificant." The correct statement about significant figures is: "They are digits that describe the accuracy of measurement." I appreciate your understanding. Question 8 The Erlenmeyer flask and thermometer used in this investigation are made of glass. In the event an item breaks, which of the following steps should be taken to dispose of the glass in the household trash? Use a broom and dustpan to collect the glass in a hard-sided container before disposal. (CORRECT) Use a broom and dustpan to collect the glass for disposal directly into the trash. Use gloved hands to collect the glass into a hard-sided container before disposal. Use bare hands to collect the glass into a hard-sided container before disposal. Use gloved hands to collect the glass for disposal directly into the trash. The correct step to take to dispose of the glass in the household trash in the event an item breaks is:

"Use a broom and dustpan to collect the glass in a hard-sided container before disposal." This method helps ensure safety and minimizes the risk of injury from broken glass. Question 9 How many significant figures are in the number 9641.25? 0, Unselected, 0 3, Unselected, 3 2, Unselected, 2 4, Unselected, 4 6, Unselected, 6 (CORRECT) Pre-Lab Assessment Result You have not passed the pre-lab assessment. You must score 100% to unlock the rest of the investigation. Please review the pre-lab sections again before re-attempting this assessment. You have unlimited attempts to pass this assessment. Click the Review Pre-Lab button to be returned to the start of the pre-lab section. Review Pre-Lab Pre-Lab Assessment Result Congratulations!!! You passed the Pre-lab Assessment.

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