QUESTION The degree of agreement among several measurements of the same quantity is called __________. It reflects the reproducibility of a given type of measurement. a) accuracy b) error c) precision d) significance e) certainty

QUESTION The agreement of a particular value with the true value is called a) accuracy b) error c) precision d) significance e) certainty

QUESTION The amount of uncertainty in a measured quantity is determined by: a) both the skill of the observer and the limitations of the measuring instrument. b) neither the skill of the observer nor the limitations of the measuring instrument. c) the limitations of the measuring instrument only. d) the skill of the observer only. e) none of these

QUESTION One second contains this many picoseconds. a) 1 × 1012 b) 1 × 10–12 c) 1 × 10–9 d) 1 × 109 e) 1 × 1015

Rules for Counting Significant Figures (number of digits that contribute to precision) All non-zero digits are significant figures: 1234  4 significant figures Zeros between non-zero digits (captive zeros) are significant figures: 205  3 significant figures Zeros beyond decimal point at the end of the number (trailing) are significant figures: 0.24000  5 significant figures 6

Rules for Counting Significant Figures (number of digits that contribute to precision) Zeros preceding the first non-zero digit in a number are not significant figures: 0.00453  3 significant figures Zeros at the end of whole numbers are not significant figures unless you are given information in different way; 3400  2 significant figures, 34.00 X 102  4 significant figures, 3400.  4 significant figures. 7

How many significant figures are in each of the following? 12  2 significant figures (S.F.) 1098  4 S.F. 2001  4 S.F. 2.001 x 103  4 S.F. 0.0000101  3 S.F. 1.01 x 10-5  3 S.F. 1000.  4 S.F. (because of the decimal point). 22.04030  7 S.F. 8

QUESTION A scientist obtains the number 0.045006700 on a calculator. If this number actually has four (4) significant figures, how should it be written? a) 0.4567 b) 0.4501 c) 0.045 d) 0.04500 e) 0.04501

QUESTION How many significant figures are there in the number 3.1400? d) 4 e) 5

QUESTION How many significant figures are there in the number 0.04560700? a) 4 b) 5 c) 7 d) 8 e) 9

Rules for Significant Figures in Mathematical Operations Multiplication and division: The number of significant figures in the result is the same as that in the quantity with the smallest number of significant figures. Ex.: 4.56 x 1.4 = 6.38  6.4 (3 S.F.) (2 S.F.) (3 S.F.) (2 S.F.) The product should have only two significant figures since 1.4 has two significant figures. 12

Rules for Significant Figures in Mathematical Operations Addition and subtraction: The result has the same number of decimal places as the least precise measurement used in the calculation. Ex.: 12.11 + 18.0 + 1.013  31.128  31.1 The correct result is 31.1, since 18.0 has only one decimal place. 13

QUESTION Using the rules of significant figures, calculate the following: 6.167 + 83.0 5.10 a) 17.5 b) 18 c) 17 d) 20 e) 17.48

QUESTION Using the rules of significant figures, calculate the following: 4.0021 – 0.004 a) 3.998 b) 4 c) 3.9981 d) 4.00 e) 4.0

Rules for Rounding of Data In series of calculations, carry the extra digits through to the final result, then round. If the digit to be removed; a. Is less than 5, the preceding digit stays the same. Example: 1.33 rounds to 1.3 b. Is equal to or greater than 5, the preceding digit is increased by 1. Example: 1.36 rounds to 1.4 16

Units Conversion How do you convert 1.53 minutes to seconds? a. Find a conversion factor (or factors) : 60 sec = 1 min b. Set up start-up and ending information with units 1.53 min. = sec c. We need an answer in ‘sec’ and we need to get rid of ‘min’. Therefore, 1.53 min X 60 sec/1 min = 91.8 sec. 17

QUESTION The mass of 24 kg equals a) 0.024 g b) 0.24 g c) 240 g d) 2400 g e) 2.4 x 104 g

QUESTION Convert 0.6571 m to mm. a) 657.1 mm b) 6.571 x 10-3 mm c) 6.571 x 10-4 mm d) 0.06571 mm e) none of these

QUESTION Convert 5687.4 g to mg. a) 5.6874 mg b) 56.784 mg c) 568.74 mg d) 5.6874 x 103 mg e) 5.6874 x 106 mg

Temperature Measurement Three systems for measuring temperature are given below; The Celsius scale (oC) The Kelvin scale (K) The Fahrenheit scale (oF) Following Four equations (formula) are used for introversion of temperature scales. 21

Temperature Measurement TK = TC + 273.15 ……………(1) TC = TK – 273.15………….... (2) TF = TC X 9 oF / 5 oC + 32 oF…. (3) TC = (TF – 32 oF ) 5 oC / 9 oF…….(4) 22

The Three Major Temperature Scales Cont. The Three Major Temperature Scales 23

A person has a temperature of 102.5 oF. What is this Example: A person has a temperature of 102.5 oF. What is this temperature on the Celsius scale? On the Kelvin scale? By using equation; TC = (TF - 32 oF) 5 oC / 9 oF = (102.5 oF - 32 oF) 5 oC / 9 oF = 39.2 oC TK = TC + 273.2 = (39.2 + 273.2 ) K = 312.4 K 24

QUESTION The melting point of lead is 327°C. What is this on the Fahrenheit scale? (TF = TC × (9°F/5°C) + 32°F) a) 620.6°F b) 600°F c) 895°F d) 621°F e) 547°F

Density Density: The mass of substance per unit Volume of the Substance. D= m/v Density = mass(g)/volume(cm3)  g/cm3 Density is often used as an “identification tag” for a substance. 26

QUESTION The density of gasoline is 0.7025 g/mL at 20°C. When gasoline is added to water: a) it will float on top. b) it will sink to the bottom. c) it will mix so you can’t see it. d) the mixture will improve the running of the motor. e) none of these things will happen.

QUESTION A sample containing 33.42 g of metal pellets is poured into a graduated cylinder initially containing 12.7 mL of water, causing the water level in the cylinder to rise to 21.6 mL. Calculate the density of the metal.

Matter 1. Solid is rigid, it has a fixed volume and shape. 2. Liquid has a definite volume but no specific shape, it assumes the shape of its container. 3. Gas has no fixed volume or shape, it takes on the shape and volume of its container. 29

Density and Matter 30

MIXTURE and COMOUNDS A MIXTURE is a combination of two or more substances that are not chemically united and do not exist in fixed proportions to each other. Most natural substances are mixtures. Example air is the mixture of several gases, petroleum etc.

MIXTURE and COMOUNDS MIXTURES PURE COMPOUNDS A mixture can be physically separated into pure compounds or elements.  A pure compound has a constant composition with fixed ratios of elements.  Mixtures may exhibit a changing set of physical properties. For example, mixture of alcohol and water boils over a range of temperatures. Physical properties such as boiling point or melting point of pure substances are invariant. For example, pure water boils at 100 degrees oC.

Types of Mixtures Homogeneous mixture: Having visibly indistinguishable parts. Physical properties are the same throughout the material. A homogeneous mixture a solution (example: vinegar). 33

Types of Mixtures Heterogeneous mixtures: Having visibly distinguishable parts. Physical properties are different at different points in a material (example: bottle of ranch dressing (salad dressing made of buttermilk, garlic, onion, herbs, spices etc). 34

Definitions Physical change: A change in the form of a substance but not in its chemical composition. E.g. conversion of ice into water. Chemical change: when a given substance becomes a new substance or substances with different properties and different composition. Burning of wood or gas. 35

Definitions Pure substance: is one with constant composition. Pure substances can be isolated by separation techniques – distillation, filtration, chromatography. Compound: is a substance with constant composition that can be broken down into elements by chemical processes. Example: electrolysis of water produces hydrogen and oxygen. 36

QUESTION _________ are substances with constant composition that can be broken down into elements by chemical processes. a) Solutions b) Mixtures c) Compounds d) Quarks e) Heterogeneous mixtures

QUESTION A method of separation that employs a system with two phases of matter, a mobile phase and a stationary phase, is called a) filtration. b) chromatography. c) distillation. d) vaporization. e) homogenization.

Exercise 30. Indicate the number of significant figures in each of the following: a. This book contains more than 1000 pages. b. A mile is about 5300 ft. c. A liter is equivalent to 1.059 qt. d. The population of the United States is approaching 3.0 102 million. e. A kilogram is 1000 g. f. The Boeing 747 cruises at around 600 mi/h.

Exercise 32. How many significant figures are in each of the following? a. 100 one S.F. e. 0.0048 two S.F. b. 1.0 × 102 two S.F. f. 0.00480 three S.F. c. 1.00 × 103 three S.F. g. 4.80 × 103 three S.F. d. 100. three S.F. h. 4.800 × 103 foure S.F.

Exercise 2.26 8.4 × 1022 1.5 × 105 6.67 × 1012

Exercise a. TC = TK  273 = 233  273 = -40 °C 56. Convert the following Kelvin temperatures to Celsius and Fahrenheit degrees. a. the temperature that registers the same value on both the Fahrenheit and Celsius scales, 233 K b. the boiling point of helium, 4 K c. the temperature at which many chemical quantities are determined, 298 K d. the melting point of tungsten, 3680 K a. TC = TK  273 = 233  273 = -40 °C TF = 9/5 × TC + 32 = 9/5 × (-40.) + 32 = -40 °F b.TC = 4 -273 = -269 °C; TF = 9/5 × (-269) + 32 = -452 °F TC = 298 - 273 = 25 °C; TF = × 25 + 32 = 77 °F TC = 3680 - 273 = 3410 °C; TF = 9/5 × 3410 + 32 = 6170 °F

Exercise 66. The density of pure silver is 10.5 g/cm3 at 20 °C. If 5.25 g of pure silver pellets is added to a graduated cylinder containing 11.2 mL of water, to what volume level will the water in the cylinder rise? 5.25 g × 1 cm3/10.5 g = 0.500 cm3 = 0.500 mL The volume in the cylinder will rise to 11.7 mL (11.2 mL + 0.500 mL = 11.7 mL).

Exercise 34. Use exponential notation to express the number 385,500 to a. one significant figure. 4 × 105 b. two significant figures. 3.9 × 105 c. three significant figures. 3.86 × 105 d. five significant figures. 3.8550 × 105

Exercise 74. Define the following terms: solid, liquid, gas, pure substance, element, compound, homogeneous mixture, heterogeneous mixture, solution, chemical change, physical change.

When you know chemistry, there’s a new level of looking at the world around you.