chapter 2-3 outline. problems

# chapter 2-3 outline. problems - Chapter 2 Outline The...

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Chapter 2 Outline The Importance Of Measurements - Qualitative Measurements – give results in a descriptive nonnumeric form - Quantitative Measurements – give results in a definite form, usually as numbers Accuracy and Precision - Accuracy – how close a single measurement comes to the actual dimension or true value of whatever is measured · Can depend upon only one measurement - Precision – how close several measurements are to the same value · Dart analogies · Precision measurements depend upon more than one measurement Scientific Notation - Scientific Notation – a number is written as the product of two numbers: · A coefficient · A power of 10 36,000 --> 3.6 x 10 4 0.0081 --> 8.1 x 10 -3 - To Multiply: · Multiply the coefficients · Add the exponents - To Divide: · Divide the coefficients · Subtract the exponents - To Add or Divide: · The exponents must be made the same Significant Figures in Measurements - Significant Figures – in a measurement: include all the digits that are know precisely plus one last digit that is estimated - Rules: · Every non-zero digit is significant

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· Zeros between non-zero digits are significant · Zeros in front of non-zero digits are not significant · Zeros at the end of a number are significant · Zeros to the right of a decimal point are significant · Zeros as place markers are not significant --> 300 · Zeros as measured values are significant --> 3.0 x 10 2 - Unlimited Numbers of Significant Digits: · Counting --> exact # of people =unlimited # of Significant Figures · Exactly defined quantities --> 60 min = 1 hr Significant Figures in Calculations - An answer cannot be more precise than the least precise measurement from which it was calculated - Addition and Subtraction: · Rounded to the same number of decimal places as the measurement with the least number of decimal places - Multiplication and Division: · Rounded to the number of significant figures in the least precise measurement with the least number of significant figures The International System of Units, SI - The International System of Units (SI) – a revised version of the metric system Units of Length - Meter (m)– the basic SI unit of length or linear measure Units of Volume - Volume – the space occupied by any sample of matter - Liter (L) – the volume of a cube that is 10 cm along each side · 10 cm x 10 cm x 10 cm = 1000 cm 3 = 1 L 1 L = 1 dm 3 Units of Mass - Weight – a force; the measure of a pull on a given mass by the earth’s gravity - Kilogram (kg) – the basic SI unit of mass · The mass of an object measured by comparing it to 1 kg
- Gram (g) – 1/1000 of a kilogram and is a more commonly used unit of mass because a kilogram is very large Measuring Density · Density – the ratio of the mass of an object to its volume Specific Gravity

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## This note was uploaded on 09/22/2008 for the course CHEM 2090 taught by Professor Zax,d during the Fall '07 term at Cornell.

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chapter 2-3 outline. problems - Chapter 2 Outline The...

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