01 Laboratory Skill Review-1

# 01 Laboratory Skill Review-1 - 1 01 Laboratory Skill Review...

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01 Laboratory Skill Review Scientific Measurements and the Metric System Objectives To understand how to make measurements utilizing various instruments To learn how to use the metric system To convert between the metric system and the English (American) System of length, volume, mass and temperature for measurements To apply metric measurements in future laboratories To express calculations and measurements to an appropriate level significance These exercises cover math and map skills that you will be using in future labs. Since these skills often cause big time issues in future labs, because of varied skill levels, we use the first lab of the semester to get everyone up to speed. If you are already strong in these areas, you should finish today’s lab quickly. If, however, you are weaker, you may need more time. Show ALL work. (You may use a calculator.) Inequalities 6 > 2 means 6 is greater than 2. 4 < 10 means that 4 is less than 10. 2 < X < 4 means X is a number greater than 2 and less than 4. (The alligator mouth opens towards the larger meal!) 1. Insert correct symbol 10 ____ 100 2. Insert correct symbol: 100 ____ 1 3. Use symbols and variable X to describe a number between 6 and 18. 4. Use symbols and variable X to describe a number that is less than 2.5. Scientific notation Scientific notation is a simpler way of writing long numbers. Scientific Notation requires that the final number be between 1 and 10 . For example, 23 x 10 -4 is not in scientific notation. (Solve these without a calculator!) 45600 = 4.56 x 10 4 For numbers ≥ 10, move the decimal to the left and the exponent is +. 0.000678 = 6.78 x 10 -4 For numbers < 1, move the decimal to the right and the exponent is –. 5. Write in scientific notation: 0.0000237 6. Write in scientific notation: 120,400 7. Write out (expanded): 2.5 x 10 -6 8. Write out (expanded): 3.9 x 10 4 Introduction For scientists to communicate their results to other scientists around the world, there must be some uniformity in units of which their data are expressed. In this week’s lab, you will practice making precise quantitative measurements; you will learn to interpret and to convert those measurements in a uniform way; and you will learn to express the precision of your measurement. 1

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A. MEASUREMENT PRECISION AND SIGNIFICANT FIGURES In science it is important to be honest when reporting values. A measurement cannot be more precise than the equipment used to make the measurement. In making a calculation, we must report the final value with no more precision than the least precise value used in the calculation. We achieve this by controlling the number of significant figures used to report the measurement. The number of significant figures in a measurement, such as 9.15647, is equal to the number of digits that are confidently known (9,1,5,6,4 in this example) plus the last digit (7 in this example), which is an estimate or approximation. As we improve the sensitivity of the equipment used to make a measurement, the number of significant figures increases.
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