Chapter 1 Chemistry PDF

Introduction 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...

Introduction 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 2  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 3  The Study of Chemistry Macroscopic Microscopic 4 The scientific method is a systematic approach to research. A hypothesis is a tentative explanation for a set of observations. tested modified 5 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 6 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 7 A mixture is a combination of two or more substances in which the substances retain their distinct identities. 1. Homogenous mixture – composition of the mixture is the same throughout soft drink, milk, solder 2. Heterogeneous mixture – composition is not uniform throughout cement, iron filings in sand 8 Physical means can be used to separate a mixture into its pure components. magnet distillation 9 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 10 Replace with Table 1.1 from 7e page 6 11 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 12  Classification of Matter Replace with Table 1.5 from 7e page 7 13 A Comparison: The Three States of Matter 14 The Three States of Matter: Effect of a Hot Poker on a Block of Ice 15  Types of Changes A physical change does not alter the composition or identity of a substance. sugar dissolving ice melting in water A chemical change alters the composition or identity of the substance(s) involved. hydrogen burns in air to form water 16  Extensive and Intensive Properties An extensive property of a material depends upon how much matter is being considered. mass length volume An intensive property of a material does not depend upon how much matter is being considered. density temperature color 17 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 weight = c x mass A 1 kg bar will weigh on earth, c = 1.0 1 kg on earth on moon, c ~ 0.1 0.1 kg on moon 18 International System of Units (SI) Replace table with Table 1.2 on page 9 19 Replace table with Table 1.3 on page 10 20 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 21 Density – SI derived unit for density is kg/m3 1 g/cm3 = 1 g/mL = 1000 kg/m3 mass density = volume m d= V 22 23 Example 1.1 Gold is a precious metal that is chemically unreactive. It is used mainly in jewelry, dentistry, and electronic devices. A piece of gold ingot with a mass of 301 g has a volume of 15.6 cm3. Calculate the density of gold. gold ingots Example 1.1 Solution We are given the mass and volume and asked to calculate the density. Therefore, from Equation (1.1), we write A Comparison of Temperature Scales K = 0C + 273.15 273.15 K = 0 0C 373.15 K = 100 0C 0F = 9 x 0C + 32 5 32 0F = 0 0C 212 0F = 100 0C 26 Example 1.2 (a) Solder is an alloy made of tin and lead that is used in electronic circuits. A certain solder has a melting point of 224°C. What is its melting point in degrees Fahrenheit? (b) Helium has the lowest boiling point of all the elements at 2452°F. Convert this temperature to degrees Celsius. (c) Mercury, the only metal that exists as a liquid at room temperature, melts at 238.9°C. Convert its melting point to kelvins. Example 1.2 Solution These three parts require that we carry out temperature conversions, so we need Equations (1.2), (1.3), and (1.4). Keep in mind that the lowest temperature on the Kelvin scale is zero (0 K); therefore, it can never be negative. (a) This conversion is carried out by writing (b) Here we have 2 1345.52 OC (c) The melting point of mercury in kelvins is given by 2 512.05 K  Dimensional Analysis Method of Solving Problems 1. Determine which unit conversion factor(s) are needed 2. Carry units through calculation 3. 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 x = desired unit given unit 29 Example 1.5 A person’s average daily intake of glucose (a form of sugar) is 0.0833 pound (lb). What is this mass in milligrams (mg)? (1 lb = 453.6 g.) Example 1.5 Strategy The problem can be stated as ? mg = 0.0833 lb The relationship between pounds and grams is given in the problem. This relationship will enable conversion from pounds to grams. A metric conversion is then needed to convert grams to milligrams (1 mg = 1 × 10−3 g). Arrange the appropriate conversion factors so that pounds and grams cancel and the unit milligrams is obtained in your answer. Example 1.5 Solution The sequence of conversions is Using the following conversion factors we obtain the answer in one step: Example 1.5 Check As an estimate, we note that 1 lb is roughly 500 g and that 1 g = 1000 mg. Therefore, 1 lb is roughly 5 × 105 mg. Rounding off 0.0833 lb to 0.1 lb, we get 5 × 104 mg, which is close to the preceding quantity. Example 1.6 A liquid helium storage tank has a volume of 275 L. What is the volume in m3? A cryogenic storage tank for liquid helium. Example 1.6 Strategy The problem can be stated as ? m3 = 275 L How many conversion factors are needed for this problem? Recall that 1 L = 1000 cm3 and 1 cm = 1 × 10−2 m. Example 1.6 Solution We need two conversion factors here: one to convert liters to cm3 and one to convert centimeters to meters: 1000 cm3 1 × 10-2 m and 1L 1 cm Because the second conversion deals with length (cm and m) and we want volume here, it must therefore be cubed to give 3 1 × 10-2 m 1 × 10-2 m 1 × 10-2 m 1 × 10-2 m × × = 1 cm 1 cm 1 cm 1 cm This means that 1 cm3 = 1 × 10-6 m3. Now we can write 3 1000 cm 3 1 × 10-2 m ? m3 = 275 L × × = 0.275 m3 1L 1 cm Example 1.6 Check From the preceding conversion factors you can show that 1 L = 1 × 10-3 m3. Therefore, a 275-L storage tank would be equal to 275 × 10-3 m3 or 0.275 m3, which is the answer. Example 1.7 Liquid nitrogen is obtained from liquefied air and is used to prepare frozen goods and in low-temperature research. The density of the liquid at its boiling point (−196°C or 77 K) is 0.808 g/cm3. Convert the density to units of kg/m3. liquid nitrogen Example 1.7 Strategy The problem can be stated as ? kg/m3 = 0.808 g/cm3 Two separate conversions are required for this problem: Recall that 1 kg = 1000 g and 1 cm = 1 × 10−2 m. Example Solubility A process by which a solute dissolves in a solvent (physical change and not a chemical change). 40 Example Example SOLUTION Example (2)