Unit 1 Scientific Measurement Homework Read pages 11

Unit 1 Scientific Measurement

Homework Read pages 11 -13 HW: Unit 1 Significant Figures Quiz: October 1 st or 2 nd

Qualitative Measurements Give results in a descriptive, nonnumeric form: hot cold big little heavy light short tall Qualitative measurements are often influenced by the measurer’s perception.

Quantitative Measurements Give results in a definite form, typically a number with units: 100 °C 32 °F 10 gal. 30 ml 11. 4 g/cm 3 0. 5 g/cm 3 10 ft. 3 ft. A quantitative measurement is only as accurate as the instrument and method used to take the measurement.

Accuracy and Precision l Accuracy - a measure of how close a measurement is to the true value of whatever is being measured l Precision – a measure of how close a series of measurements are to one another

Significant Figures l In Mathematics all numbers are exact; for example: 1 = 1. 000000 l In Science, numbers that are from data that is measured or calculated from measurements, are limited in the number of significant figures they can use. 1 ≠ 1. 00 ? ?

Significant figures l The significant figures in a measurement include all of the digits that are known. l Calculated values depend on the number of significant figures in the values used in the calculations.

Significant Figures For Example: Using a meter stick, that has markings 1 mm apart, to measure the diameter of a can you might get 38 mm. l Using calipers, that read to. 01 mm, to measure the same can, you might get 37. 79 mm. l The caliper measurement has more significant figures than the meter stick measurement. l

Significant figures Rules of significant figures: Any nonzero digit (1, 2, 3, 4, 5, 6, 7, 8, 9) is significant. Example: 23. 5 has 3 significant figures l Any zero that is sandwiched in between two nonzero digits is significant. Examples: 3200. 04 has 6 significant figures 403. 2 has 4 significant figures l

Significant figures l Zeros in front of non-zero numbers are not significant. l Zeros at the end of a number without a decimal point are not significant Examples: 0. 00079 and 650, 000 each have 2 significant figures.

Significant figures A zero to the right of the rightmost nonzero digit : a) Is significant if there is a decimal anywhere in the number. Examples: 0. 000040 has 2 significant figures 973. 4000 has 7 significant figures b) Is not significant if there is no decimal in the number. Examples: 10, 000 has 1 significant figure 5960 has 3 significant figures l

Significant figures l Some numbers are exact numbers, and have an infinite amount of significant figures. l Example: Integers, the results of counting, are exact. 2 whole apples, means exactly 2, or 2. 00000. . . to infinity.

Significant Figures Some numbers can only be expressed with scientific notation!!! l Example: Express 1000 with 2 significant figures. l 1000 – has only 1 sig. fig. l 1000. - has 4 sig. figs. l 1. 0 x 10³ has 2 sig. figs.

Unit 1 – Sig Figs 2 a. qual b. qual c. quant d. both 3. Lisa – not accurate or precise Lamont – accurate and precise Leigh Ann – precise, not accurate 4 a. 3 b. 2 c. 4 d. 4 e. 3 f. 3 5 a. 98. 5 L b. 0. 000763 cg c. 57. 0 m d. 0. 00750 mm