Chemistry: The Study of Change   Chapter 1 Copyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display.

Chemistry: A Science for the 21st Century Health and Medicine Sanitation systems Surgery with anesthesia Vaccines and antibiotics Gene therapy Energy and the Environment Fossil fuels Solar energy Nuclear energy

Chemistry: A Science for the 21st Century Materials and Technology Polymers, ceramics, liquid crystals Room-temperature superconductors? Molecular computing? Food and Agriculture Genetically modified crops “Natural” pesticides Specialized fertilizers

The Study of Chemistry Macroscopic Microscopic

Qualitative data consists of general observations about the system The coffee is hot The boy is tall Quantitative data comprises numbers obtained by various measurements of the system. The coffee is heated to 97°C John is 5 ft 6 in tall

The scientific method is a systematic approach to research A hypothesis is a tentative explanation for a set of observations tested modified

Force = mass x acceleration A law is a concise statement of a relationship between phenomena that is always the same under the same conditions. Force = mass x acceleration A theory is a unifying principle that explains a body of facts and/or those laws that are based on them. Atomic Theory

Problem 1.3 Classify the following statement as (a) qualitative (b) quantitative 1.The sun is approximately 93 million miles from earth. 2. Leonardo daVinci was a better painter than Michelangelo. 3.Ice is less dense than water. 4.Butter tastes better than margarine.

Problem 1.4 (a) Classify the following statement as a (a) hypothesis (b) law (c) theory 1.Beethoven’s contribution to music would have been much greater if he had married. 2. An autumn leaf gravitates toward the ground because there is an attractive force between the leaf and the earth. 3. All matter is composed of very small particles called atoms

Chemistry is the study of matter and the changes it undergoes Matter is anything that occupies space and has mass. A substance is a form of matter that has a definite composition and distinct properties. liquid nitrogen gold ingots silicon crystals

Heterogeneous mixture – composition is not uniform throughout. A mixture is a combination of two or more substances in which the substances retain their distinct identities. Homogenous mixture – composition of the mixture is the same throughout. clear juice (apple, cranberry), bronze, solder Heterogeneous mixture – composition is not uniform throughout. cement, iron filings in sand

Physical means can be used to separate a mixture into its pure components. distillation magnet

dry ice – carbon dioxide A compound is a substance composed of atoms of two or more elements chemically united in fixed proportions. Compounds can only be separated into their pure components (elements) by chemical means. lithium fluoride quartz dry ice – carbon dioxide

114 elements have been identified An element is a substance that cannot be separated into simpler substances by chemical means. 114 elements have been identified 82 elements occur naturally on Earth gold, aluminum, lead, oxygen, carbon, sulfur 32 elements have been created by scientists technetium, americium, seaborgium Element 118 discovered in 2006!

Classifications of Matter

Problem 1.16(a) Classify the following as a(n) (a) element (c) homogeneous mixture (b) compound (d) heterogeneous mixture filtered sea water Helium gas Kosher salt (sodium chloride) A bottle of soda (capped, unshaken) A milkshake Filtered air in a bottle concrete

A Comparison: The Three States of Matter

The Three States of Matter: Effect of a Hot Poker on a Block of Ice solid liquid gas

Types of Changes A physical change does not alter the composition or identity of a substance. ice melting sugar dissolving in water A chemical change alters the composition or identity of the substance(s) involved. hydrogen burns in air to form water

Problem 1.12(a) Does the following describe a (a) chemical change or a (b) physical change? The helium gas inside of a balloon tends to leak out after a few hours. Frozen orange juice is reconstituted by adding water to it. The growth of plants depends on the sun’s energy in a process called photosynthesis. A spoonful of table salt dissolves in a bowl of soup.

Extensive and Intensive Properties An extensive property of a material depends upon how much matter is is being considered. mass length volume An intensive property of a material does not depend upon how much matter is is being considered. density temperature color

Interestingly, the process of measuring mass is called weighing! Matter - anything that occupies space and has mass. mass – measure of the quantity of matter SI unit of mass is the kilogram (kg) 1 kg = 1000 g = 1 x 103 g weight – force that gravity exerts on an object W = m x a SI unit of force is the Newton (N) 1 N = 1 kg∙m/s2 Interestingly, the process of measuring mass is called weighing!

A 1 kg mass weighs almost 6 times more on earth than on the moon! Mass is constant, while weight is dependent on location On the moon, a = 1.67 m/s2 W = m x a = 1 kg x 1.67 m/s2 1.67 Newton On earth, a = 9.81 m/s2 W = 1 kg x 9.81 m/s2 = 9.81 kg∙m/s2 9.81 Newton 9.81 Newton/1.67 Newton = 5.87 A 1 kg mass weighs almost 6 times more on earth than on the moon!

International System of Units (SI)

Volume – SI derived unit for volume is cubic meter (m3) 1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3 1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3 1 L = 1000 mL = 1000 cm3 = 1 dm3 1 mL = 1 cm3

Density – SI derived unit for density is kg/m3 1 g/cm3 = 1 g/mL = 1000 kg/m3 density = mass volume d = m V A piece of platinum metal with a density of 21.5 g/cm3 has a volume of 4.49 cm3. What is its mass?

Problem 1.22 The density of ethanol, a colorless liquid that is commonly known as grain alcohol, is 0.798 g/mL. Calculate the mass of 17.4 mL of the liquid.

A Comparison of Temperature Scales 1K K = (0C + 273.15 0C) 1 0C 273 K = 0 0C 373 K = 100 0C 0F = x 0C + 32 0F 9 0F 5 0C 32 0F = 0 0C 212 0F = 100 0C

Convert 327.5 0C to degrees Fahrenheit. Convert 172.9 0F to degrees Celsius. Convert 77 K, the boiling point of liquid nitrogen to degrees Celsius.

Problem 1.24(a) Normally the human body can endure a temperature of 105 °F for only short periods of time without permanent damage to the brain and other vital organs. What is the temperature in °C?

Problem 1.24(b) Ethylene glycol is a liquid organic compound that is used as an antifreeze in car radiators. It freezes at -11.5 °C. Calculate the freezing point in °F.

Problem 1.24(c) The temperature of the surface of the sun is about 6300 °C. What is this temperature is °F?

Problem 1.24(d) The ignition temperature of paper is 451 °F. What is the temperature in K?

Scientific Notation The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000,000 6.022 x 1023 The mass of a single carbon atom in grams: 0.0000000000000000000000199 1.99 x 10-23 N x 10n N is a number between 1 and 10 n is a positive or negative integer

Scientific Notation Addition or Subtraction 568.762 0.00000772 move decimal left move decimal right n > 0 n < 0 568.762 = 5.68762 x 102 0.00000772 = 7.72 x 10-6 Addition or Subtraction Write each quantity with the same exponent n Combine N1 and N2 The exponent, n, remains the same 4.31 x 104 + 3.9 x 103 = 4.31 x 104 + 0.39 x 104 = 4.70 x 104

Scientific Notation Multiplication Division (4.0 x 10-5) x (7.0 x 103) = (4.0 x 7.0) x (10-5+3) = 28 x 10-2 = 2.8 x 10-1 Multiply N1 and N2 Add exponents n1 and n2 Division 8.5 x 104 ÷ (5.0 x 109)= (8.5 ÷ 5.0) x 104-9 = 1.7 x 10-5 Divide N1 and N2 Subtract exponents n1 and n2

Significant Figures Any digit that is not zero is significant 1.234 kg 4 significant figures Zeros between nonzero digits are significant 606 m 3 significant figures Zeros to the left of the first nonzero digit are not significant 0.08 L 1 significant figure If a number is greater than 1, then all zeros to the right of the decimal point are significant 2.0 mg 2 significant figures If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant 0.00420 g 3 significant figures

How many significant figures are in each of the following measurements? 24 mL 3001 g 0.0320 m3 6.4 x 104 molecules 560 kg

Problem 1.34 How many significant figures are in each of the following measurements? 0.006 L 0.0605 dm 60.5 mg 605.5 cm2 960 x 10-3 g 6 kg 60 m

Significant Figures Addition or Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers. 89.332 1.1 + 90.432 one significant figure after decimal point round off to 90.4 3.70 -2.9133 0.7867 two significant figures after decimal point round off to 0.79

Significant Figures Multiplication or Division The number of significant figures in the result is set by the original number that has the smallest number of significant figures 4.51 x 3.6666 = 16.536366 = 16.5 3 sig figs round to 3 sig figs 6.8 ÷ 112.04 = 0.0606926 = 0.061 2 sig figs round to 2 sig figs

Significant Figures Exact Numbers Numbers from definitions or counted numbers of objects are considered to have an infinite number of significant figures The average of three measured lengths; 6.64, 6.68 and 6.70? 6.64 + 6.68 + 6.70 3 = 6.67333 = 6.67 = 7 Because 3 is an exact number

Carry out the following arithmetic operations to the correct number of significant figures. 11,254.1 g + 0.1983 g 66.59 L – 3.113 L 8.16 m x 5.1355 0.0154 kg ÷ 88.3 mL 2.64x103 cm + 3.27x102 cm

Carry out the following arithmetic operations to the correct number of significant figures. 9.1 g – 4.682 g 7.1x104 dm x 2.2654x102 dm 6.54 g ÷ 86.5542 mL 7.55x104 m – 8.62x103 m

Problem 1.36 Carry out the following operations as if they were calculations of experimental results, and express each answer in the correct units with the correct number of significant figures 7.310 km ÷ 5.70 km (3.26 x 10-3 mg) – (7.88 x 10-5) mg (4.02 x 106 dm) + (7.74 x 107 dm) (7.8 m – 0.34 m)/(1.15 s + 0.82 s)

Accuracy – how close a measurement is to the true value Precision – how close a set of measurements are to each other accurate & precise precise but not accurate not accurate & not precise

Problem 1.38 Three apprentice tailors (X,Y, and Z) are assigned to the task of measuring the seam of a pair of trousers. The results in inches are: X (31.5, 31.6, 31.4) Y (32.8, 32.3, 32.7) Z (31.9, 32.2, 32.1) The true length is 32.0 in. Comment on the precision and accuracy of each tailor’s measurements.

Dimensional Analysis Method of Solving Problems Determine which unit conversion factor(s) are needed Carry units through calculation If all units cancel except for the desired unit(s), then the problem was solved correctly. given quantity x conversion factor = desired quantity desired unit given unit given unit x = desired unit

Dimensional Analysis Method of Solving Problems How many mL are in 1.63 L? Conversion Unit 1 L = 1000 mL 1L 1000 mL 1.63 L x = 1630 mL 1L 1000 mL 1.63 L x = 0.001630 L2 mL

The speed of sound in air is about 343 m/s The speed of sound in air is about 343 m/s. What is this speed in miles per hour? conversion units meters to miles seconds to hours 1 mi = 1609 m 1 min = 60 s 1 hour = 60 min 343 m s x 1 mi 1609 m 60 s 1 min x 60 min 1 hour x = 767 mi hour

Problem 1.46 The current speed limit in some states in the US is 55 miles per hour. What is the speed limit in km/hr? (1 mi = 1609 m)

Problem 1.66 Vanillin is the substance whose aroma the human nose detects in the smallest amount. The threshold limit is 2.0 x 10-11g per liter of air. If the current price of 50 g of vanillin is $112, determine the cost (in cents) to supply enough vanillin so that the aroma could be detected in a large aircraft hanger with a volume of 5.0 x 107 ft3