Objectives Review on significant figures Revisit on Measurement

Objectives • Review on significant figures. • Revisit on Measurement Reading. • Resolve the issue on METERSTICK READING.

Homework Return the quiz papers tomorrow, June 18, 2013.

SIGNIFICANT FIGURES

What do you know about the SIGNIFICANT FIGURES ?

What is the SIGNIFICANCE OF SIGNIFICANT FIGURES ? What do significant figures tell us?

• The SIGNIFICANT FIGURES are digits of measurement known with a degree of certainty. absolute certainty • The SIGNFICANT FIGURES are composed of the certain digits and the estimate. • The SIGFINIFICANT FIGURES tells us how powerful an instrument is. Precision

The Significance of Significant Figures • It tells us the degree of precision of our instrument and the measurement. • It gives us confidence when describing things.

Indicate the number of significant figures. a. b. c. d. 12 5 000 501 e. 8. 0 f. 8. 10 g. 9. 100 h. 0. 001

Indicate the number of significant figures. a. b. c. d. 12 5 000 501 e. 8. 0 f. 8. 10 g. 9. 100 h. 0. 001 The absence of units makes everything INSIGNIFICANT.

Role of Units • The units make our measurements certain. Before anything else, check whether the units are present.

Indicate the number of significant figures. a. b. c. d. 12 m (2 sig figs) 5 000 cm 50 000 km 501 mi e. 8. 0 g f. 8. 10 cg g. 9. 100 dg h. 0. 001 kg All non-zero digits are significant.

Indicate the number of significant figures. a. b. c. d. 12 m 5 000 cm 50 000 km 501 mi (1) e. 8. 0 g f. 8. 10 cg g. 9. 100 dg h. 0. 001 kg Zeros at the end of a non-zero digit without a decimal point may or may not be significant. (Le. May et. al. , 2000)

Indicate the number of significant figures. a. b. c. d. 12 m 5 000 cm 50 000 km 501 mi (3) e. 8. 0 g f. 8. 10 cg g. 9. 100 dg h. 0. 001 kg Zeros in between significant digits are significant.

Indicate the number of significant figures. a. b. c. d. 12 m 5 000 cm 50 000 km 501 mi e. 8. 0 g f. 8. 10 cg g. 9. 100 dg h. 0. 001 kg (2) (3) (4) Zeros that fall both at the end of a non-zero digit and after the decimal point are always significant.

Indicate the number of significant figures. a. b. c. d. 12 m 5 000 cm 50 000 km 501 mi e. 8. 0 g f. 8. 10 cg g. 9. 100 dg h. 0. 001 kg (1) These zeros merely indicate the place of the decimal point.

PRECISION vis-à-vis SIGFIG Which measurement shows the greatest precision? 1 cm 1. 000 cm 1 cm, 2 cm, 3 cm, … 1. 0 cm, 1. 1 cm, 1. 2 cm, … 1. 00 cm, 1. 01, 1. 02 cm, . . . 1. 000 cm, 1. 001 cm, 1. 002 cm, …

PRECISION vis-à-vis SIGFIG 1. 00 cm vs. 1. 00 m

PRECISION vis-à-vis SIGFIG 10 m vs. 1 m

Count their NUMBERS. 10 apples 15 oranges

Issue in the SIG FIG • Counting numbers used in measurement have infinite number of SIG FIG. (Elliot, 2009) • Counting numbers used in measurement are digits that are all significant. • Counting numbers used in measurement have indefinite number of SIG FIG.

Ways to Make Digits Significant • The Bar • The Decimal point • Scientific Notation

Express the following measures in ONE significant figure. a. b. c. d. e. 2 000 mi 1 255 g 30 minutes 0. 0046 mm 0. 1005 m

Express the following measures in ONE significant figure. a. b. c. d. e. 2 000 mi 1 255 g 30 minutes 0. 0046 mm 0. 1005 m a. b. c. d. e. 2 x 103 mi 1 x 103 g 3 x 101 minutes 5 x 10 -3 mm 1 x 10 -1 m

Rule on SIG FIG in Problem Solving • Check if the problem involves multiplication and division. • If it does, check your answers in the LEAST number of significant figures based on the given.

Example What is the area of the rectangle whose sides are 12 cm and 10. cm?

Rule on SIG FIG in Problem Solving • When numbers are added or subtracted, the last significant figure in the answer occurs in the last column (counting from left to right) containing a number that results from a combination of digits that are all significant. (Cutnell and Johnson, 2007)

Rule on SIG FIG in Problem Solving • Check if the problem involves addition and/or subtraction. • If it does, express your answers based on the LEAST precise measurement.

Example 41. 2 cm + 41. 25 cm 40 cm 122. 45 cm 120 cm

Rule on SIG FIG in Problem Solving • Check if the problem involves addition and/or subtraction. • If it does, express your answers LEAST number of decimal places. (Le. May, et. al. 2000)

Example 41. 2 cm + 41. 25 cm 40 cm 122. 45 cm 122 cm

The End.

Example + 4. 22 x 102 4. 23 x 103 cm cm

Example + 422 cm 4230 cm 4652 cm 4650 cm

Example + 4. 22 x 102 4. 23 x 103 4. 652 x 103 4. 65 x 103 cm cm

Example 4. 22 x 102 + 42. 3 x 102 46. 52 x 102 4. 65 x 103 cm cm

Solve for the answer. a. b. c. d. e. f. g. h. i. j. (3. 78 x 103 m) – (1. 368 x 103 m) (2. 00 x 104 s) (9. 9 x 102 s) 3 cm) (8. 01 x 102 cm) + (7. 8 x 1010 (9. 3 x 10 -5 N) ÷ (3. 10 x 10 -1)N) (6. 0 x 104 in) (3. 20 x 10 -2 in) (5. 3 x 10 -8 g) + (4. 83 x 10 -8 g) (1. 25 x 104 km) ÷ (2. 5 x 102)km) (7. 85 x 10 -1 L) + (2. 3 x 10 -2 L) (2. 2 x 104 m. L) (3. 20 x 102)m. L) (1. 24 x 101 kg) – (5. 0 x 1010 kg)

Write your answers on the board.