Created by: Lauren Sniscak SI System Created by: Lauren Sniscak

SI Units In 1960, this international agreement was reached specifying particular choice of metric units for use in scientific measurements Named after the French Système International d’Unités Has 7 base units from which all other units are derived

SI Base Units Physical Quantity Name of Unit Abbreviation Mass Kilogram kg Length Meter m Time Second s, sec Temperature Kelvin K Amount of substance Mole mol Electric current Ampere A Luminous intensity Candela cd

Prefixes Prefix Abbreviation Meaning Giga G 109 Mega M 106 Kilo k 103 Deci d 10-1 Centi c 10-2 Milli m 10-3 Micro μ 10-6 Nano n 10-9 Pico p 10-12 Femto f 10-15 Prefixes — Used to indicate decimal fractions or multiples of various units

Mass Length Meter is the SI base unit A distance only slightly longer than a yard 1m = 1.09yd A measure of the amount of material in an object Kilogram is the SI base unit 1kg = 2.20lb

Temperature Measure of hotness or coldness of an object Determines the direction of heat flow Always flows spontaneously from a substance of a higher temperature to one at a lower temperature Celsius scale is the everyday scale of temperature in most countries

Temperature (cont.) Kelvin is the SI unit of temperature Historically based on properties of gases Zero is the lowest obtainable temperature on this scale (-273.15oC): referred to as absolute zero Kelvin and Celsius both have the same size degrees K = oC + 273

Volume Cubic meter (m3) is the basic SI unit Another commonly used unit of volume is liter (L) 1L = 1dm3 The liter is not an SI unit 1cm3 = 1mL Those terms are used interchangeably in volume

Reading Volume Always read the volume at: Eye level The Meniscus (bottom of the liquid curve)

Uncertainty in Measurement Exact numbers-those whose values are known exactly Have defined values Result from counting numbers of an object Inexact numbers-those whose values have some uncertainty Always exists in measured quantities Counting very large numbers of objects

Precision and Accuracy Both terms are often used in discussing uncertainties of measured values Precision-measure of how closely individual measurements agree with one another Accuracy-refers to how closely individual measurements agree with the correct, or “true,” value

Precision and Accuracy (cont.) Accuracy – closeness to “true” or accepted value Percent error Precision – many trials; reproducibility Standard deviation

(cont.)

Significant Figures Measured quantities are generally reported in such a way that only the last digit is uncertain Significant figures-all digits of a measured quantity, including the uncertain one

Conceptual Problem 3.1 Counting Significant Figures in Measurements 1. How many significant figures are in each measurement? a. 123 m d. 22 meter sticks b. 40,506 mm e. 0.07080 m c. 9.800 x 104 m f. 98,000 m Practice Problems 2. Count the significant figures in each length. a. 0.05730 meters c. 0.00073 meter b. 8765 meters d. 40.007 meters 3. How many significant figures are in each measurement? a. 143 grams c. 8.750 x 10-2 gram b. 0.074 meter d. 1,072 meters

Sample Problem 3.1 Rounding Measurements 1. Round off each measurement to the number of significant figures shown in parentheses. Write the answers in scientific notation. a. 314.721 meters (four) b. 0.001775 meter (two) c. 8792 meters (two) Practice Problems 2. Round each measurement to three significant figures. Write your answers in scientific notation. a. 87.073 meters d. 9009 meters b. 4.3621 x 108 meters e. 1.7777 x 10-3 meter c. 0.01552 meter f. 629.55 meters 3. Now round each measurement from 2. to one significant figure. Write each of your answers in scientific notation.

Sample Problem 3.2 Significant Figures in Addition 1. Calculate the sum of the three measurements. Give the answer to the correct number of significant figures. 12.52 meters + 349.0 meters + 8.24 meters = _______ Practice Problems 2. Perform each operation. Express your answers to the correct number of significant figures. a. 61.2 meters + 9.35 meters + 8.6 meters = _______ b. 9.44 meters – 2.11 meters = _______ c. 1.36 meters + 10.17 meters = _______ d. 34.61 meters – 17.3 meters = _______ 3. Find the total mass of three diamonds that have masses of 14.2 grams, 8.73 grams, and 0.912 gram.

Sample Problem 3.3 Significant Figures in Multiplication and Division 1. Perform the following operations. Give the answers to the correct number of significant figures. a. 7.55 meters x 0.34 meter = _______ b. 2.10 meters x 0.70 meter = _______ c. 2.4526 meters / 8.4 = _______ Practice Problems 2. Solve each problem. Give the answers to the correct number of significant figures. a. 8.3 meters x 2.22 meters = _______ b. 8432 meters / 12.5 = _______ c. 35.2 seconds x 1 minute = _______ 60 seconds 3. Now round each measurement from 2. to one significant figure. Write each of your answers in scientific notation.