Chapter 1: Measurements

Order of Operations Start with calculations inside ( ) Exponents and Logs are calculated next Multiplication and Division follow Addition and subtraction are last

1.1: Units of Measurement PropertyMetric UnitUS UnitConversion LengthMeter (m)Inch (in)1m = 39.4 in 1in = 2.54 cm VolumeLiter (L)Quart (qt)1L = 1.06 qt 1qt = 946 mL MassKilograms (kg) Pound (lb)1kg = 2.20 lb 1lb = 454 g TempDeg CelsiusDeg Fahrenheit

1.2: Scientific Notation Large Numbers: 12,000,000 = 1.2 x 10 7 Small Numbers: = 1.2 x Short hand: Mass of a proton = 1.67 x kg Easier to determine magnitude: kg A lake has 1,320,000,000 liters of water. What is its volume in scientific notation?

1.3: Measured and Exact Numbers Measured Numbers: Uncertainty and error in measurement Mass of an apple is measured to be roughly 486g Exact Numbers: From definition or counting items The number of apples in a sack is exactly 6 There are exactly 12 inches in a foot

1.4: Significant Figures All measured values have error Accurate measurements are close to actual value Precise measurements are repeatable Significant figures are used to track digits of importance through calculations Good explanation of sig figs is given on page 10

Sig Figs Continued Only used for measured numbers not exact All non-zero digits are significant Zeroes may or may not be significant (significant if at end of a decimal number or between non-zero digits) 21.0 has 3 sig figs and has 4 sig figs has 1 sig fig but has 2 sig figs 400 has 1 sig fig unless it’s actually 4.00 x 10 2 which has 3 sig figs (sci. not. tracks sig figs) 2012 has 4 sig figs

1.5: Sig Figs in Calculations Rounding off: –If first digit dropped is 4 or less the number is rounded down. If it is 5 or more the number is rounded up Multiplication and Division: –The number with the lesser amount of sig figs determines the sig figs in the answer Addition and Subtraction: –The number with the lesser amount of decimal places is used to determine decimal places in the answer

Examples of Sig Figs in Calculations The number 19.4 is rounded to 19 but the number 19.5 is rounded to x =  / 2 = 75  =  – 1.42 =  Be careful, the calculator may not display correct number of Sig Figs!

1.6 Metric and SI System Prefixes PrefixAbbreviationConversion Mega M1,000,000 Kilo k1, Centi c1/100 Milli m1/1,000 Micro μ1/1,000,000

Volume and Converting Cubic Units 1000 mL = 1 L 1 mL = 1 cm 3 = 1 cc 100 cm = 1 m 100 cm 3 IS NOT = 1 m 3 (1m) 3 = (100 cm) 3 = 1,000,000 cm 3

1.7: Conversion Factors Used for converting units and used A LOT in chemistry! Step 1 – Identify information given Step 2 – Plan how to reach desired units Step 3 – Select necessary conversion factors Step 4 – Set up conversions so they cancel Step 5 – Solve problem and determine sig figs* Unit should cancel leaving you with desired units

1.8: Density The relationship between mass and volume Density can be used as a conversion factor Specific gravity is unitless but roughly equal to density numerically

1.9: Temperature Measures how hot or cold things are Measure in Fahrenheit, Celcius and Kelvin scales Can NOT be converted simply using conversion factors Different 0° temps for each scales