Metric System

Measurement Measurement is the basic part of science Imagine how you would measure the length of an object, mass of a substance, or distance from one place to another without measurements Numbers and units are used to make measurements To make practical measurements, a measurement standard must be used Standard is a fixed quantity used by everyone when measuring

SI System Scientists all over the world use one universal system, SI System SI=International System of Units All SI units and standards are agreed upon and understood by scientists all over the world In the SI system, prefixes are used to make the basic units larger or smaller by multiples of ten

SI Base Units Length=meter (m) Mass=kilogram (kg) Temperature=kelvin (K) Time=seconds (s) Amount of Substance=mole (mol) Electric Current=ampere (A)

Metric Prefixes Prefix Symbol Meaning Multiply Unit By Giga- G Billion (109) 1,000,000,000 Mega- M Million (106) 1,000,000 Kilo- k Thousand (103) 1000 Deci- d Tenth (10-1) 0.1 Centi- C Hundredth (10-2) 0.01 Milli- Thousandth (10-3) 0.001 Micro- µ Millionth (10-6) 0.000001 Nano- N Billionth (10-9) 0.000000001

SI for Temperature Kelvin scale is the SI unit for temperature Kelvin=°C + 273 Zero Kelvin is the same as absolute zero Point in which all molecular motion stops

Limits of Measurement Precision Accuracy Gauge of how exact a set measurements are to one another More precision=more significant figures All the digits that are known in a measurement, plus the last digit that is estimated Accuracy Closeness of a measurement to the actual value of what is being measured

Significant Figures in Measurements Significant figures in measurements include all of the digits that are known, plus a last digit that is estimated Measurements must always be reported to the correct number of significant figures because calculated answers often depend on the number of significant figures in the values used in the calculation Also known as sig figs

Rules For Determining Whether a Digit is Significant 1) Every nonzero digit in a reported measurement is assumed to be significant. Ex) 24.7 m, 0.743 m, and 714 m all have 3 sig figs 2) Zeros appearing between nonzero digits are significant. Ex) 7003 m, 40.79 m, and 1.503 m all have 4 sig figs 3) Leftmost zeros appearing in front of nonzero digits are not significant. They act as place holders Ex) 0.0071 m, 0.42 m, 0.00099 m all have only 2 sig figs

Rules For Determining Whether a Digit is Significant 4) Zeros at the end of a number and to the right of a decimal point are always significant. Ex) 43.00 m, 1.010 m, and 9.000 m each have 4 sig figs 5) Zeros at the rightmost end of a measurement that lie to the left of an understood decimal point are not significant if they serve as placeholders to show the magnitude of the number. Ex) The zeros in 300 m, 7000 m, and 20,000 are not significant. The sig fig values for these numbers is one

Density Density is a physical property Density is the mass of a material per unit of volume Standard Unit=g/cm3 The density of a substance may be used to help identify the substance

Density 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3 Platinum Platinum Mercury Aluminum Platinum Platinum Mercury Mercury 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3

Density Equation Using algebrae, we can solve for all three substances (density, volume, and mass) by manipulating the equations: Density=Mass/Volume Mass=Density X Volume Volume=Mass/Density

Volume Volume is the amount of space an object takes up 1 cm3=1 mL Volume=Length x Width x Height

Problem 1 A piece of copper has a mass of 57. 54 g. It is 9 Problem 1 A piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).