CHEM 1211k 1st Edition Lecture 2Outline of Last Lecture I. Chapter 1: Matter, Measurement, and Problem SolvingChapter 1: Matter, Measurement, and Problem Solving… (continued)II. 1.7 Counting Significant FiguresA. All nonzero digits are significant-Ex. 1.5 has 2 sig figs Interior zeros are significant- Ex. 1.05 has 3 sig figs Leading Zeros are NOT significant- Ex. 0.00105 has 3 sig figs Trailing zeros may or may not be significant. Trailing Zeros after a decimal point are significant and only significant if the number contains a decimal point.-Ex. 1.050 has 4 sig figsB. Exact numbers have an unlimited number of significant figures.- Ex. 1 cm is exactly equal to 0.01m; 1cm=0.01m (unlimited) Radius of a circle = diameter of the circle/2C. Practice Problems!1. 0.04450 m= 4 sig figs2. 5.003 km= 5 sig figs3. 10 dm=1m= unlimited sig figs4. 1.000 X 10^5 s= 4 sig figs5. 0.00002 mm= 1 sig fig6. 10,000 m= 1 sig figD. Significant Figures in CalculationsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. When multiplying or dividing measurements with significant figures, the result has the same number of significant figures as the measurement with the fewest significant figures.- Ex. 5.02 X 89.665 X 0.10= 45.0018= 45 (because the number with the fewest significant figures is 0.10 and it has 2 significant figures.) When adding or subtracting measurements with significant figures, the result has the same number of decimal places as the measurement with the lowest number of decimal places.- Ex. 2.345 + 0.07 + 2.9975= 5.4125= 5.41 (because the number with lowest number of decimal places is 0.07 and it only has two decimal places.) When doing different operations with significant figures:1. Do whatever is in parentheses first2. Evaluate the significant figures in the intermediate answer3. Then do the remaining steps-Ex. 3.489 x (5.67- 2.3)= 3.37= 3.4 3.489 x 3.4= 11.8626= 12III. 1.8 Solving Chemical ProblemsA. Always write every number with its associated unit.B. Conversion factors are relationships between two units: may be exact or measured.C. Arrange conversion factors so the starting unit cancels. You don’t need to know the relationship as long as you can find something else the starting and desired units are related to.D. Precision and Accuracy- Precision is an indication of how close repeated measurements are to each other how reproducible a measurement is. Random error can result in the inconsistency.- Accuracy is an indication of how close a measurement comes to the actual value of the quantity.- Random error – error that has equal probability of being too high or too low.- Systematic error – error that tends toward being either too high or too low.Chapter 1: Matter, Measurement, and Problem Solving…