1 CHEMISTRY 101 Dr. IsmailFasfous  Textbook : Raymond Chang, 10th Edition  Office Location: Chemistry Building, Room 212  Office Telephone: 4738  &  Website:

2 Chapter 1 Chemistry: The Study of Change

1.2 The Study of Chemistry MacroscopicMicroscopic We can see, touch and measureWe cannot without technology

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Steps in the Scientific Method 1.Observations  quantitative (water boils at 100 oC)  qualitative (the sky is blue) 2.Formulating hypotheses  a tentative explanation for the observation 3.Performing experiments  gathering new information to decide whether the hypothesis is valid whether the hypothesis is valid 1.3

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

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 weight = c x mass on earth, c = 1.0 on moon, c ~ A 1 kg bar will weigh 1 kg on earth 0.1 kg on moon

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 Measurement Measurement - quantitative observation consisting of 2 parts Part 1 - number Part 2 - scale (unit) Part 2 - scale (unit)Examples: 20 grams 6.63    Joule seconds 1.7

8 The Fundamental SI Units

9

10 Measurement of volume 1 L = 1000 mL = 1000 cm 3 = 1 dm 3 1 mL = 1 cm 3 1.7

11 Common types of laboratory equipment used to measure liquid volume. 1.7

Density is the mass of substance per unit volume of the substance – 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 1.7

13 A cubic piece of a silver metal measures 4.25 cm on each edge. If the density is g/cm 3, what is the mass of the cube? Mass = d.V. = (4.25cm) 3 x g/cm 3 = 805 g A piece of iron metal with a density of 7.87 g/cm 3 has a volume of 5.94 cm 3. What is its mass?0 d = m V m = d x V = 7.87 g/cm 3 x 5.94 cm 3 = 46.7 g

K = 0 C F = x 0 C K = 0 0 C 373 K = C 32 0 F = 0 0 C F = C

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) =

16 Uncertainty in Measurement A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty.

ml 20.17ml 20.15ml 20.18ml ±0.01ml Figure : Measurement of volume using a buret. The volume is read at the bottom of the liquid curve (called the meniscus).

18 Precision and Accuracy Accuracy refers to the agreement of a particular value with the true value. Precision refers to the degree of agreement among several elements of the same quantity.

accurate & precise but not accurate & not precise Precision and Accuracy

20 Rules for Counting Significant Figures - Overview 1.Nonzero integers (1-9) 2.Zeros  leading zeros, before (1-9)  captive zeros, between (1-9)  trailing zeros, after (1-9) 3.Exact numbers

21 Rules for Counting Significant Figures - Details Nonzero integers always count as significant figures has 4 sig figs.

22 Rules for Counting Significant Figures - DetailsZeros  Leading zeros do not count as significant figures has 3 sig figs.

23 Rules for Counting Significant Figures - DetailsZeros  Captive zeros always count as  Captive zeros always count as significant figures has 4 sig figs.

24 Rules for Counting Significant Figures - DetailsZeros  Trailing zeros are significant only  Trailing zeros are significant only if the number contains a decimal point has 4 sig figs.

25 Rules for Counting Significant Figures - Details Exact numbers have an infinite number of significant figures. Independent of measuring device: 1 apple, 10 students, 5 cars…. 2πr The 2 is exact and 4/3 π r 2 the 4 and 3 are exact From Definition: 1 inch = 2.54 cm exactly The 1 and 2.54 do not limit the significant figures Average of certain values = = 7.67 Because 3 is an exact number = 8

26 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

27 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

has 3 sig. fig. = 1.00 x has 1 sig. fig. = 1 x 10 2 Scientific Notation

29 Rules For Rounding 1.In a series of calculations, carry the extra digits through to the final result, then round. 2.If the digit to be removed: A.Is less than 5, then no change e.g rounded to 2 sig. fig = 1.3 B.Is equal or greater than 5, the preceding digit increase by 1 e.g rounded to 2 sig. fig = 1.4

30 Rules for Significant Figures in Mathematical Operations Multiplication and Division: # Sig figs in the result equals the number in the least precise measurement used in the calculation  2.0 =  13 (2 sig figs)

31 Rules for Significant Figures in Mathematical Operations Multiplication and Division: 4.51 x = = sig figsround to 3 sig figs 6.8 ÷ = sig figsround to 2 sig figs = 0.061

32 Rules for Significant Figures in Mathematical Operations Addition and Subtraction: # decimal places in the result equals the number of decimal places in the least precise measurement =  18.7 (3 sig figs)

33 Rules for Significant Figures in Mathematical Operations Addition and Subtraction: round off to 90.4 one significant figure after decimal point two significant figures after decimal point round off to 0.79

34 Determine the number of significant figures in each of the following measured quantities? a) m (3) b) 2.90x10 8 g (3) c) cm (6) d) L (4) Practice

35 Round off the following to three significant figures: a) m = 265 m b) 30 g = 30.0 g c) 3275 ml = 3.28 x 10 3 ml d) 2.2x10 -5 mm = 2.20 x10 -5 mm Practice

36 Perform the following calculations and round off the answer to the proper significant figures: m m – 8.01 m m = 0.3m g/ (23.5ml + 10 ml) = 2.4g/ml g x (11.9ml - 7 ml) = 245g/ml=200g/ml g x (12.1ml-7ml)=255g/ml=300g/ml Practice

37 Proper use of “unit factors” leads to proper units in your answer: 2.54 cm = 1 inch 1 inch/2.54 cm = 1 Unit factor What is the length in inch of 2.85 cm pencil 2.85 (cm) x 1 (inch)/2.54(cm) = 2.85/2.54 = 1.12 in Dimensional Analysis Method of Solving Problems

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

39 Perform the following conversions: a) mm to nm (0.0033mm)(1m/1000mm)(10 9 nm/1m) = 3300nm b) 0.67 pm to cm (0.67pm)(1m/ pm)(100cm/1m) = 6.7 x cm c) 4.60x10 -6 kg/L to mg/ ml (4.60x10 -6 kg/L)(1000g/1kg)(1000mg/1g)(1L/1000ml) = 4.60 x mg/ml Practice

The speed of sound in water is about 1482 m/s. What is this speed in miles per hour? 1 mi = 1609 m1 min = 60 s1 hour = 60 min 1482 m s x 1 mi 1609 m 60 s 1 min x 60 min 1 hour x = 3316 mi hour meters to miles seconds to hours 1.9 conversion units Practice

Convert the density g/cm 3 to units of kg/m 3 ? 1 kg = 1000g 1 cm 3 = 1 x m g cm 3 x 1 kg 1000 g 1 cm 3 1x10 -6 m 3 x = 808 kg m 3 conversion units Practice