Conversion Factors and Calculations Lab 2

Conversion Factors and Calculations Lab 2

Conversion Factors and Calculations Lab 2 focuses on essential mathematical principles for converting units and performing calculations in scientific contexts. It covers significant figures, rounding rules, and the application of conversion factors in various measurements. Students will learn how to calculate area and volume, perform unit conversions, and understand the importance of precision in scientific measurements. This lab is designed for students in chemistry or physics courses, providing practical exercises to enhance their understanding of measurement and calculation techniques.

Key Points

  • Explains significant figures and rounding rules for accurate calculations.
  • Covers unit conversions and the application of conversion factors in scientific measurements.
  • Includes practical exercises for calculating area and volume of solids.
  • Demonstrates the importance of precision in scientific experiments.
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ConversionFactors in Calculations
Pre-lab Study Questions
1. What are the rules for rounding off numbers?
If the first number to be dropped is less than 5, drop it and all following numbers. If the first
number to be dropped is 5 or greater, drop the numbers and increase the last retained digit by
one.
2. How do you determine the number of significant figures in an answer obtained by multiplying or
dividing?
Answers for multiplication/division keep the same number of significant figures as the
measured number with the fewest significant figures.
3. How is the number of digits determined when an answer is obtained by adding or subtracting?
For addition/subtraction, an answer has the same number of decimal places as the measured
number with the fewest decimal places.
4. Is a body temperature of 39.4°C a normal temperature or does it indicate a fever?
The temperature 39.4 indicates a fever. Normal body temperature is 39.0°C. Converting
39.4°C to Fahrenheit gives
1.8 (39.4°C ) + 32 = 102.9°C
5. What is
an equality and how is it used to write a conversion factor?
An equality is the same measurement expressed in two different units. A conversion factor is
written by placing one of the units in the numerator and the other in the denominator. The
two are reversed for a second factor for the equality.
A. Rounding Off
A.1 Rounding A student rounded off the following calculator display to three significant figures.
Indicate if the rounded number is correct. If incorrect, round off the display value properly.
Calculator Student’s Correct (yes/no) Corrected (if needed)
Display Rounded Value
24.4704 24.5 Yes
143.63212 144 Yes
532, 800 530 No 533, 000
0.00858345 0.009 No 0.00858
8 8.00 Yes
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Report Sheet - Lab 2
A.2 Area
Your measurements Another student’s measurements
Length = 13.29 cm 13.25 cm
Width = 4.32 cm 4.35 cm (3 sig figs)
Area = 57.4 cm
2
57.6 cm
2
(Show calculations)
13.29 cm X 4.32 cm = 57.4 cm
2
13.25 cm X 4.35 cm = 57.6 cm
2
(3 sig figs)
Why could two students obtain difference values for the calculated areas of the same rectangle?
The estimated digit in each measurement will give some variation in the last digit of the
calculated area.
A.3 Volume of A Solid by Direct Measurement
Shape of solid rectangular solid
Formula for volume of solid L X W X H = V
height 2.85 cm length 4.82 cm
width 2.85 cm diameter (if cylinder) _____________
Volume of the solid 39.2 cm
3
(Show calculations of volume including the units)
4.82 cm X 2.85 cm X 2.85 cm = 39.2 cm
3
(3 sig figs)
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Report Sheet - Lab 2
B. Significant Figures In Calculations
B.1 Perform the following multiplication and division calculations. Give a final answer with the
correct number of significant figures:
4.5 ✕ 0.28 1.3
0.1184 ✕ 8.00 ✕ 0.0345 0.0300
(42.4)(15.6) 5.23
1.265
(35.56)(1.45) 19
(4.8)(0.56)
B.2 Perform the following addition and subtraction calculations. Give a final answer with the correct
number of significant figures.
13.45 mL + 0.4552 mL 13.91 mL (2 decimal places)
145.5 m + 86.58 m + 1045 m 1277 m
1315 + 200 + 1100 2600 (last sig fig in hundreds place)
245.625 g - 80.2 g 165.4 g
4.62 cm - 0.885 cm _ 4.53
Questions and Problems
Q.1 What is the total mass in grams of objects that have masses of 0.2000 kg, 80.0 g, and 524
mg?
0.2000 kg X 1000 g/1 kg = 200.0 g
524 X 1 g/1000 mg = 0.524 g
Add 200.0 g + 80.0 g + 0.524 g = 280.5 g (one decimal place)
Q.2 A beaker has a mass of 225.08 g. When a liquid is added to the beaker, the combined mass is
238.254 g. What is the mass in grams of the liquid?
238.254 g – 225.08 g = 13.17 g (two decimal places)
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FAQs of Conversion Factors and Calculations Lab 2

What are significant figures and why are they important?
Significant figures are the digits in a number that contribute to its precision. They include all non-zero digits, any zeros between significant digits, and trailing zeros in the decimal portion. Understanding significant figures is crucial in scientific calculations to ensure accuracy and reliability in measurements. Using the correct number of significant figures helps convey the precision of the data and avoids misleading conclusions.
How do you convert units using conversion factors?
Unit conversion involves using conversion factors, which are ratios that express how many of one unit are equal to another. For example, to convert centimeters to meters, you would use the conversion factor of 100 cm = 1 m. By multiplying the measurement by the appropriate conversion factor, you can change the units while maintaining the same quantity. This process is essential in scientific calculations where different units are commonly used.
What is the formula for calculating the volume of a rectangular solid?
The volume of a rectangular solid can be calculated using the formula V = L × W × H, where L is the length, W is the width, and H is the height of the solid. This formula allows students to determine the capacity of three-dimensional objects, which is essential in various scientific applications. Accurate volume calculations are important in experiments where precise measurements of liquids or solids are required.
What is the importance of rounding in scientific calculations?
Rounding is important in scientific calculations to ensure that the results are presented with the appropriate level of precision. When performing calculations, especially with significant figures, rounding helps to avoid overstating the accuracy of the results. The rules for rounding dictate that if the first digit to be dropped is less than five, it is removed, while if it is five or greater, the last retained digit is increased by one. This practice maintains the integrity of the data.
How do you calculate the area of a rectangle?
To calculate the area of a rectangle, you multiply its length by its width using the formula A = L × W. This calculation provides the total surface area of the rectangle, which is essential in various scientific and practical applications. Understanding how to calculate area is fundamental in fields such as geometry, physics, and engineering, where spatial dimensions are frequently analyzed.

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