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

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

2 2 Chemistry: A Science for the 21 st Century Health and Medicine Sanitation systems Surgery with anesthesia Vaccines and antibiotics Gene therapy Energy and the Environment Fossil fuels Solar energy Nuclear energy

3 3 Chemistry: A Science for the 21 st Century Materials and Technology Polymers, ceramics, liquid crystals Room-temperature superconductors? Molecular computing? Food and Agriculture Genetically modified crops Natural pesticides Specialized fertilizers

4 4 The Study of Chemistry MacroscopicMicroscopic

5 5 The scientific method is a systematic approach to research A hypothesis is a tentative explanation for a set of observations tested modified

6 6 A theory is a unifying principle that explains a body of facts and/or those laws that are based on them. A law is a concise statement of a relationship between phenomena that is always the same under the same conditions. Atomic Theory Force = mass x acceleration

7 7 Chemistry In Action: In 1940 George Gamow hypothesized that the universe began with a gigantic explosion or big bang. Experimental Support expanding universe cosmic background radiation primordial helium Primordial Helium and the Big Bang Theory

8 8 Matter is anything that occupies space and has mass. A substance is a form of matter that has a definite composition and distinct properties. Chemistry is the study of matter and the changes it undergoes liquid nitrogen gold ingots silicon crystals

9 9 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. 2. Heterogeneous mixture – composition is not uniform throughout. soft drink, milk, solder cement, iron filings in sand

10 10 Physical means can be used to separate a mixture into its pure components. magnet distillation

11 11 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

12 12

13 13 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

14 14 Classifications of Matter

15 15 A Comparison: The Three States of Matter

16 16 The Three States of Matter: Effect of a Hot Poker on a Block of Ice solid liquid gas

17 17 A physical change does not alter the composition or identity of a substance. A chemical change alters the composition or identity of the substance(s) involved. ice melting sugar dissolving in water hydrogen burns in air to form water Types of Changes

18 18 An extensive property of a material depends upon how much matter is is being considered. An intensive property of a material does not depend upon how much matter is is being considered. mass length volume density temperature color Extensive and Intensive Properties

19 19 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 10 3 g weight – force that gravity exerts on an object A 1 kg bar will weigh 1 kg on earth 0.1 kg on moon weight = c x mass on earth, c = 1.0 on moon, c ~ 0.1

20 20 International System of Units (SI)

21 21

22 22 Volume – SI derived unit for volume is cubic meter (m 3 ) 1 cm 3 = (1 x m) 3 = 1 x m 3 1 dm 3 = (1 x m) 3 = 1 x m 3 1 L = 1000 mL = 1000 cm 3 = 1 dm 3 1 mL = 1 cm 3

23 23 Density – SI derived unit for density is kg/m 3 1 g/cm 3 = 1 g/mL = 1000 kg/m 3 density = mass volume d = m V A piece of platinum metal with a density of 21.5 g/cm 3 has a volume of 4.49 cm 3. What is its mass? d = m V m = d x V = 21.5 g/cm 3 x 4.49 cm 3 = 96.5 g

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25 25 K = 0 C F = x 0 C K = 0 0 C 373 K = C 32 0 F = 0 0 C F = C A Comparison of Temperature Scales

26 26 Convert F to degrees Celsius. 0 F = x 0 C F – 32 = x 0 C 9 5 x ( 0 F – 32) = 0 C C = x ( 0 F – 32) C = x (172.9 – 32) =

27 27 Chemistry In Action On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mars atmosphere 100 km (62 miles) lower than planned and was destroyed by heat. 1 lb = 1 N 1 lb = 4.45 N This is going to be the cautionary tale that will be embedded into introduction to the metric system in elementary school, high school, and college science courses till the end of time.

28 28 Scientific Notation The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000, x The mass of a single carbon atom in grams: x N x 10 n N is a number between 1 and 10 n is a positive or negative integer

29 29 Scientific Notation n > = x 10 2 move decimal left n < = 7.72 x move decimal right Addition or Subtraction 1.Write each quantity with the same exponent n 2.Combine N 1 and N 2 3.The exponent, n, remains the same 4.31 x x 10 3 = 4.31 x x 10 4 = 4.70 x 10 4

30 30 Scientific Notation Multiplication 1.Multiply N 1 and N 2 2.Add exponents n 1 and n 2 (4.0 x ) x (7.0 x 10 3 ) = (4.0 x 7.0) x ( ) = 28 x = 2.8 x Division 1.Divide N 1 and N 2 2.Subtract exponents n 1 and n x 10 4 ÷ 5.0 x 10 9 = (8.5 ÷ 5.0) x = 1.7 x 10 -5

31 31 Significant Figures Any digit that is not zero is significant 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 g 3 significant figures

32 32 How many significant figures are in each of the following measurements? 24 mL2 significant figures 3001 g 4 significant figures m 3 3 significant figures 6.4 x 10 4 molecules 2 significant figures 560 kg2 significant figures

33 33 Significant Figures Addition or Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers round off to 90.4 one significant figure after decimal point two significant figures after decimal point round off to 0.79

34 34 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 = = sig figsround to 3 sig figs 6.8 ÷ = sig figsround to 2 sig figs = 0.061

35 35 Significant Figures Exact Numbers Numbers from definitions or 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? = = 6.67 Because 3 is an exact number = 7

36 36 Accuracy – how close a measurement is to the true value Precision – how close a set of measurements are to each other accurate & precise but not accurate & not precise

37 37 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 given unit x = desired unit desired unit given unit

38 38 Dimensional Analysis Method of Solving Problems Conversion Unit 1 L = 1000 mL 1L 1000 mL 1.63 L x = 1630 mL 1L 1000 mL 1.63 L x = L2L2 mL How many mL are in 1.63 L?

39 39 The speed of sound in air is about 343 m/s. What is this speed in miles per hour? 1 mi = 1609 m1 min = 60 s1 hour = 60 min 343 m s x 1 mi 1609 m 60 s 1 min x 60 min 1 hour x = 767 mi hour meters to miles seconds to hours conversion units