CHAPTER 2-GEN.-INORG.-CHEM Measurement, Significant figures etc.

Meaurement

1. CHAPTER 2: MEASUREMENTS

2. Lesson Objectives: At the end of the chapter, students should be able to: Differentiate the systems of units; Determine the significant numbers; Calculate numbers expressed in scientific notation; Discuss the difference between accuracy and precision; and Value the role of measurement in their daily life.

3. Measurement Measurement is used to describe matter quantitatively through the use of measuring instrument like meter stick, weighing scale, beaker, graduated cylinder, ruler, tape measure.

4. The International System of Units (SI) The International System of Units (SI), commonly known as the metric system, is the international standard for measurement. 

5. The International System of Units (SI) SYSTEM UNITS ENGLISH Pound, atmosphere, inch, yard, mile, bar, mil/ hr , METRIC Meter, liter, centimeter, pascal, newton, hour, second, cubic meter

6. Conventional Units of SI Units BASED/FUNDAMENTAL QUANTITIES Quantity SI Unit Length Meter (m) Mass Kilogram (kg) Time Second (s) Temperature Kelvin (K) Amount of Substance Mole (mol) Luminous Intensity Candela (cd) Electric current Ampere (A)

7. Conventional Units of SI Units DERIVED UNITS (named a few) Speed Meter per second(m/s) Acceleration Meter per second square (m/s 2 ) Force Newton (N) Pressure Pascal (Pa) Volume Cubic meter (m 3 ) Density Kilogram/cubic meter (kg/m 3 )

8. Metric Conversion Chart for Length

9. Metric Conversion Chart for Area

10. Metric Conversion Chart for Volume * 1 = 1 mL  

11. Metric Conversion Chart for Weight

12. Metric Conversion Chart for Temperature * 1 K= 272.15 ˚ C * ˚ C * ˚F * ˚C= -32 ˚)   * ˚F= 32 ˚   * ˚ C= K-273 * K= ˚ C+273

13. Metric Conversion Chart for Time

14. Common Prefixes of the Metric System

15. SIGNIFICANT FIGURES

16. SIGNIFICANT FIGURES This are digits that are significant in a certain measurement. This can be achieved by controlling the number of digits used to report the measurement. This consist of all the digits known with certainty plus one more digit that is uncertain or estimated.

17. Determining the Number of Significant Figures in a Number 1. Nonzero digits are always significant. For example, 233.1 m has four significant figures; 2.3 g has two significant figures. 2. Zeros at the beginning of a number are never significant. For example, 0.0055 L has two significant figures; 0.3456 g has four significant figures.

18. Determining the Number of Significant Figures in a Number 3. Zeros between nonzero digits are always significant. For example, 2.045 kcal has four significant figures; 8.0506 g has five significant figures. 4. Zeros at the end of a number that contains a decimal point are always significant. If no decimal point is present, trailing zeros are not significant For example, 3.00 L has three significant figures; 0.0450 mm has three significant figures; 1000 g has 1 significant figure.

19. Scientific Notation A way of representing numbers consisting of a product between a nonexponential number and 10 raised to a whole number exponent that may be positive or negative. A form of presenting very large numbers or very small numbers in a simpler form.

20. Scientific Notation Rules To determine the power or exponent of 10, we must follow the rule listed below: The base should be always 10. The exponent must be a non-zero integer, that means it can be either positive or negative. The absolute value of the coefficient is greater than or equal to 1 but it should be less than 10.  Coefficients can be positive or negative numbers including whole and decimal numbers. The mantissa carries the rest of the significant digits of the number

21. Scientific Notation

22. Converting Scientific notation to non-scientific (standard form) The following numbers are written using scientific notation. Write them without using scientific notation. 3.72 × b. 8.513 ×  

23. Converting Scientific notation to non-scientific (standard form) The exponent 5 indicates that the original position of the decimal is located 5 places to the right of the standard position. Zeros are added to accommodate this change: 3.72 x = 372,000. = 372,000   standard position original position

24. Converting Scientific notation to non-scientific (standard form) b. The exponent −7 indicates that the original position of the decimal is 7 places to the left of the standard position. Again, zeros are added as needed: 8.513 x = 0.0000008513   standard position original position

25. Converting non-scientific notation to Scientific Write the following numbers using scientific notation: 8725.6 0.000729

26. Converting non-scientific (standard form) to Scientific notation The standard decimal position is between the 8 and 7: 8.7256. However, the original position of the decimal is 3 places to the right of the standard position. Therefore, the exponent must be +3: 8725.6 = 8.7256 ×  

27. Converting non-scientific (standard form) to Scientific notation b. The standard decimal position is between the 7 and 2: 7.29. However, the original position is 4 places to the left of standard. Therefore, the exponent must be −4: 0.000729 = 7.29 ×  

28. Accuracy & Precision

29. Accuracy vs. Precision

30. If the darts are neither close to the bulls-eye, nor close to each other, there is neither accuracy, nor precision (Fig. A).   If all of the darts land very close together, but far from the bulls-eye, there is precision, but not accuracy (Fig. B).   

31. If the darts are all about an equal distance from and spaced equally around the bulls-eye there is mathematical accuracy because the average of the darts is in the bulls-eye. This represents data that is accurate, but not precise (Fig. C). However, if you were actually playing darts this would not count as a bulls-eye! If the darts land close to the bulls-eye and close together, there is both accuracy and precision (Fig. D). 

32. Examples: If the weather temperature reads 28 °C outside and it is 28 °C outside, then the measurement is said to be accurate. If the thermometer continuously registers the same temperature for several days, the measurement is also precise. If you take the measurement of the mass of a body of 20 kg and you get 17.4,17,17.3 and 17.1, your weighing scale is precise but not very accurate. If your scale gives you values of 19.8, 20.5, 21.0, and 19.6, it is more accurate than the first balance but not very precise.

33. Q1) The volume of a liquid is 26 mL. A student measures the volume and finds it to be 26.2 mL, 26.1 mL, 25.9 mL, and 26.3 mL in the first, second, third, and fourth trial, respectively. Which of the following statements is true for his measurements? They are neither precise nor accurate. They have poor accuracy. They have good precision. They have poor precision.

34. II Q2) The volume of a liquid is 20.5 mL. Which of the following sets of measurement represents the value with good accuracy? 18.6 mL, 17.8 mL, 19.6 mL, 17.2 mL 19.2 mL, 19.3 mL, 18.8 mL, 18.6 mL 18.9 mL, 19.0 mL, 19.2 mL, 18.8 mL 20.2 mL, 20.5 mL, 20.3 mL, 20.1 mL

35. III Some of the following numbers are written using scientific notation, and some are not. In each case, rewrite the number using the notation in which it is not written. 5.88 × 6. 1 × 0.000439 7. 0.102 3.915 × 8. 301000000 9870 9. 1.36 × 2.89 × 10. 36.77  

36. IV DIRECTION: Write the number of significant figure and identify what rule is involved. Two points each. 23000 km 0.0000123 Pa 1002.110 s 3.000 lbs. 23 handsome students

37. VI 10 km to mil 5.5 lbs.-gram 300m/s-km/hr. 1 liter- cubic centimeter 40-degree Fahrenheit to degree Celsius 6. 220 Kelvin to degree Fahrenheit 7. 25 years to second 8. 120 years to century 9. 34 inches to centimeters 10. 21 s to hour DIRECTION: Convert the following quantities. Two points each item.