 #  1. How does quantitative information differ from qualitative information?  2. Convert 75 kilometers to millimeters.

## Presentation on theme: " 1. How does quantitative information differ from qualitative information?  2. Convert 75 kilometers to millimeters."— Presentation transcript:

 1. How does quantitative information differ from qualitative information?  2. Convert 75 kilometers to millimeters.

 Text 59 #16-23

Significant Figures and Scientific Notation

 Good measurements are both accurate and precise. (These are not the same thing.)  Accurate (correct)—How close the measurement is to the true value  Precise (reproducible)—How close several measurements are to the same number (the measurement may be wrong)  Measure your textbook.

 Two common sources of error are human (the skill and knowledge of the person) and quality of the equipment  Accepted value—the true or correct value based on reliable resources (you can look it up in a book)  Experimental value—measured value determined by experiment in a lab  Error=accepted value minus experimental value.  Can be positive (exp. value less than actual value)  Can be negative (exp. value greater than actual value)

 Percent Error is the absolute value of the error divided by the accepted value and multiplied by 100 to get the percent. lAccepted value – experimental valuel x100 accepted value You will often calculate this value after a lab to determine your own % error.

 Significant Figures are ones which are known to be reasonably reliable. This includes all digits which are known precisely plus one last digit that is estimated.  The term significant does not mean certain.  Table 6 Page 47 Table 6 Page 47

 How many significant figures are in each of the following measurments? 1. 28. 6 g 2. 3440. cm 3. 910 m 4. 0.04604 L 5. 0.0067000 kg

 Do Practice Problems 1-2 on Page 48 in your text.

 Round to the same number of decimal places as the measurement in the calculation with the least number of decimal places.  When working with whole numbers, the answer should be rounded so that the final significant digit is in the same place as the leftmost uncertain digit. (5400 + 365 = 5800)  Example: Add 25.1 g and 2.03 g  27.1 g

 Calculate and express in the correct number of sig figs.  5.44 m – 2.6103 m  2.83 m

 Round to the number of significant figures in the least precise term used in the problem.  Example: Calculate the density of an object that has a mass of 3.05 g and a volume of 8.47 mL.  0.360 g/mL

 2.4 g/mL x 15.82 mL  38 g

 Do Practice Problems 1-4 on page 50 in text.

 When using conversion factors to change one unit to another, they are usually exact measurements.  For example, there are exactly 100 cm in a meter. This figure does not limit the degree of certainty in the answer.  Example: Convert 4.608 m to centimeters.  460.8 cm

 In scientific notation a number is written as the product of two numbers, a coefficient and a power of 10  Coefficient=a number greater than or equal to 1, but less than 10 (1.0 through 9.9)  Exponent is a whole number that indicates how many times the coefficient must be multiplied by 10 (if positive exponent) or by 1/10 (if negative exponent)

 Change a large number to scientific notation by moving the decimal to the left. The exponent will be a positive number.  65, 000 km  6.5 x 10 4 km

 Change a small number to scientific notation by moving the decimal to the right. The exponent will be negative.  0.00012 mm  1.2 x 10 -4 mm

 370.27  How many sigfigs?  How can you write this number with the correct number of sigfigs?  Use scientific notation.

 Exponents must be equal. Then add or subtract the coefficients. Be sure to put final answer in correct scientific notation to the correct number of significant figures.  4.2 x 10 4 kg + 7.9 x 10 3 kg 5.0 x 10 4 kg Now do the problem on your calculator.

 Multiply the coefficients and add the exponents algebraically.  5.23 x 10 6 μ m x 7.1 x 10 -2 μ m  3.7 x 10 5 μ m 2  Now do the problem on your calculator.

 Divide the coefficients and subtract the denominator exponent from the numerator exponent.  5.44 x 10 7 g 8.1 x 10 4 mol 6.7 x 10 2 g/mol Now do the problem on your calculator.

 Calculate the volume of a sample of aluminum that has a mass of 3.057 kg. The density of aluminum is 2.70 g/cm 3.  1.13 x 10 3 cm 3

 Solve practice problems 1-4 Text Page 54.

 Two quantities are directly proportional to each other if dividing them creates a constant value.  Example—mass and volume of a substance (density is the constant  They increase or decrease by the same factor.  When one is doubled, so is the other. When one is halved, so is the other.  Graph Page 55 Graph Page 55

 Two quantities are inversely proportional if their product is a constant.  When one is doubled the other is halved  Graph Page 56-57 Graph Page 56-57

 Make Flashcards of Common Elements  Element Quiz 9/22

 Sig Fig Worksheet  Text Page 60 #35, 36, 37, 38, 43, 45  Element Flashcards—Do not need to be turned in.  Density of Solids Lab Report Due on Friday 9/18  Print Element Survey Activity  Read Ch 1.3 Pages 16-20

Download ppt " 1. How does quantitative information differ from qualitative information?  2. Convert 75 kilometers to millimeters."

Similar presentations