Chapter 1. Matter and Measurements. Our main concern is the understanding of the principles that govern chemical reactions.

Transcription

1 Chapter 1 Matter and Measurements Our main concern is the understanding of the principles that govern chemical reactions. 1. Types of matter- pure vs mixture, element vs compound 2. Measurements uncertainties, significant figures 3. Physical properties extensive vs intensive Copyright 2001 by Harcourt, Inc. All rights reserved. Requests for permission to make copies of any part of the work should be mailed to the following address: Permissions Department, Harcourt, Inc Sea Harbor Drive, Orlando, Florida Copyright 2001 by Harcourt, Inc. All rights reserved. 1.1

2 Chapter 1 Nano Technology: Data storage, Catalyst, Optics Bio Technology: Drug, Detection, Healing Energy Technology: New Energy Source, Fuel cell Global warming, Greenhouse effect Copyright 2001 by Harcourt, Inc. All rights reserved. Requests for permission to make copies of any part of the work should be mailed to the following address: Permissions Department, Harcourt, Inc Sea Harbor Drive, Orlando, Florida Copyright 2001 by Harcourt, Inc. All rights reserved. 1.2

3 Types of matter Matter exists in three phases: solid, liquid, gas Copyright 2001 by Harcourt, Inc. All rights reserved. 1.3

4 Types of matter Elements - a substance whose atoms are all chemically same Compounds - substance containing more than one element Mixtures - two or more substance combined, retaining its chemically identity Copyright 2001 by Harcourt, Inc. All rights reserved. 1.4

5 Classification of matter Physical Processes Chemical Reaction Copyright 2001 by Harcourt, Inc. All rights reserved. 1.5

6 Elements Cannot be broken down into simpler substances Examples: nitrogen (N) lead (Pb) sodium (Na) arsenic (As) Some elements come in and out of fashion Silicon (Si, from chemical curiosity to multibillion dollar semiconductor industry) Lead (Pb, toxicity) Aluminum (Al)7.5 %, Mercury (Hg) % Copyright 2001 by Harcourt, Inc. All rights reserved. 1.6

7 Compounds Contain two or more elements with fixed mass percents Benzene, Methane C, H in different propositions has fixed composition Mass percent: compound H 2 O vs mixture of O 2 & H 2 Sodium chloride(nacl): 39.34% Na, 60.66% Cl Properties of compound vs properties of element Explosion!!!!- reactivity Glucose(C 6 H 12 O 6 ): 40.00% C, 6.71% H, 53.29% O Copyright 2001 by Harcourt, Inc. All rights reserved. 1.7

8 Mixtures Mixtures - two or more substance combined, retaining its chemically identity Homogeneous (solutions) vs. heterogeneous homogeneous : uniform in composition - soda heterogeneous : Non-uniform in composition copper sulfate & sand Separation by: filtration : separating a heterogeneous solid-liquid mixture cooper sulfate & sand & water distillation : resolving a homogeneous solid-liquid mixture cooper sulfate & water Copyright 2001 by Harcourt, Inc. All rights reserved. 1.8

9 Distillation of a homogeneous solid-liquid mixture Copyright 2001 by Harcourt, Inc. All rights reserved. 1.9

10 Result of gas-liquid chromatography of natural gas Take avantage of differences in solubility and/or extent of adsorption on a solid surface Emission Test Test people for drug or alcohol We already know the properties of compounds Copyright 2001 by Harcourt, Inc. All rights reserved. 1.10

11 TLC Thin Layer Chromatography Copyright 2001 by Harcourt, Inc. All rights reserved. 1.11

12 Measured Quantities Length : m (meter) Volume : L Mass : kg Temperature : K Copyright 2001 by Harcourt, Inc. All rights reserved. 1.12

13 Length Base unit is the meter (m) and there are couple of prefixes 1 km = 10 3 m 1 cm = 10-2 m 1 mm = 10-3 m 1 nm = 10-9 m Copyright 2001 by Harcourt, Inc. All rights reserved. 1.13

14 Volume Base unit is the liter (L) 1L = 10 3 ml = 10 3 cm 3 = 10-3 m 3 -The device commonly used to measure volumes is the graduated cylinder, pipet and buret. Copyright 2001 by Harcourt, Inc. All rights reserved. 1.14

15 Mass 1 kg = 10 3 g; 1 mg = 10-3 g -Two different balances will be used in lab. The analytical balance (± g) should be used only for accurate, quantitative work. Copyright 2001 by Harcourt, Inc. All rights reserved. 1.15

16 Temperature t F = 1.8t C + 32 T K = t C The Fahrenheit and Celsius temperature scales Convert 68 F to C and K t C = (68-32 ) / 1.8 = 20 C ; T K = 293 -Temperature is the factor that determines the direction of heat flow. Copyright 2001 by Harcourt, Inc. All rights reserved. 1.16

17 Temperature -Celsius vs Fahrenheit vs Kelvin Copyright 2001 by Harcourt, Inc. All rights reserved. 1.17

18 Experimental Error, Significant Figures -Every measurement carries with it a degree of uncertainty whose magnitute depends on the nature of the measuring device and the skill with which it is used. -The responsibility to indicate the uncertainty associated with it. -Suppose an object is weighed on a crude balance to ± 0.1g and the mass is found to be 23.6 g. This quantity contains 3 significant figures, i.e., 3 experimentally meaningful digits. With an analytical balance, mass might be g (5 sig. fig.) Copyright 2001 by Harcourt, Inc. All rights reserved. 1.18

19 Counting Significant Figures -Volume of a liquid = 24.0 ml; 3 significant figures Zeroes at the end of a measured quantity, following nonzero digits, are significant. -Volume = L; 3 significant figures (note that L = 24.0 ml) Zeroes at the beginning of a measured quantity, preceding nonzero digits, are not significant g: how many significant figure? Exponential notation: 7 x 10 2 g or 7.00 x 10 2 g Copyright 2001 by Harcourt, Inc. All rights reserved. 1.19

20 Multiplication and Division -Keep only as many significant figures are there are in the least precise quantity. -Take the smallest number of significant figures -What is the density of a piece of metal weighing g with a volume of 13.4 ml? density = g 13.4 ml = 2.70 g / ml Copyright 2001 by Harcourt, Inc. All rights reserved. 1.20

21 Addition and Subtraction - Keep only as many digits after the decimal point as there are in the least precise quantity. - Take the smallest number of decimal places - Add g of sugar to g of coffee: Total mass = g g = g Copyright 2001 by Harcourt, Inc. All rights reserved. 1.21

22 Addition and Subtraction Note that the rule for addition and subtraction does not relate to significant figures. The number of significant figures often decreases upon subtraction. Mass beaker + sample = g Mass empty beaker = g Mass sample = g (5 sig. figs.) (5 sig. figs.) (2 sig. figs.) Rounding off If the digits to be discarded are greater than 5; > 5 If the digits to be discarded are less than 5; < 5 If the digits to be discarded are 5: = 5 Copyright 2001 by Harcourt, Inc. All rights reserved. 1.22

23 Exact Numbers Certain numbers are exact rather than approximate one liter means L Copyright 2001 by Harcourt, Inc. All rights reserved. 1.23

24 Conversion Factors -One step conversions : a ratio, numerically equal to 1, by which a quantity can be converted from one set of units to another -Choose the factor that cancels out the initial unit -Multiple conversion factors Copyright 2001 by Harcourt, Inc. All rights reserved. 1.24

25 One Step Conversions A rainbow trout is measured to be 16.2 in. long. What is the length in cm? length in cm = 16.2 in 2.54 cm 1 in = 41.1 cm Note the cancellation of units. To convert from centimeters to inches, the conversion factor would be 1 in / 2.54 cm. Copyright 2001 by Harcourt, Inc. All rights reserved. 1.25

26 Multiple Conversion Factors A baseball is thrown at 89.6 miles per hour. What is the speed in meters per second? 1 mile = km = m; 1 h = 3600 s miles speed = m 1 h = 40.0 m/s h 1 mile 3600 s Copyright 2001 by Harcourt, Inc. All rights reserved. 1.26

27 Properties of Substances Intensive vs. Extensive intensive : independent of amount - density extensive : depend on amount volume, mass Chemical vs. Physical chemical : a change that converts a substance to a new one physical : without changing chemical identity Copyright 2001 by Harcourt, Inc. All rights reserved. 1.27

28 Properties of Substances Density : ratio of mass to volume Solubility : a solute dissolves in a solvent physically rather than chemical change Color : absorption spectrum Copyright 2001 by Harcourt, Inc. All rights reserved. 1.28

29 Density An empty flask weighs g. You pipet 5.00 ml of octane into the flask. The total mass is g. What is the density? d = g 5.00 ml = g / ml What is the volume occupied by ten grams of octane? g 1 ml g = 14.5 ml Copyright 2001 by Harcourt, Inc. All rights reserved. 1.29

30 Solubility Often expressed as grams of solute per 100 g of solvent: Temperature 10 C 100 C Soly. lead nitrate (g / 100 g H 2 O) How much water is required to dissolve 80 g of lead nitrate at 100 C? Mass water = 80 g lead nitrate 100 g water 140 g lead nitrate = 57 g water Copyright 2001 by Harcourt, Inc. All rights reserved. 1.30

31 Solubility Point B = Supersaturated Red line = Saturated Point A = Unsaturated Copyright 2001 by Harcourt, Inc. All rights reserved. 1.31

32 Solubility Cool the solution to 10 C. How much lead nitrate remains in solution? 50 g lead nitrate Mass of lead nitrate = 57 g water 100 g water = 28 g lead nitrate remains in solution 80 g - 28 g = 52 g lead nitrate crystallizes Copyright 2001 by Harcourt, Inc. All rights reserved. 1.32

33 Color The colors of gases and liquids are due to the selective absorption of certain components of visible light. Visible light: wavelength = 400 nm (violet) to 700 nm (red) Ultraviolet: <400 nm Infrared: >700 nm 400 nm (violet) 700 nm (red) Ultraviolet Visible light Infrared Ozone absorbs harmful, high-energy Ultraviolet radiation from the sun. CO 2 absorbs Infrared radiation given off by Earth s surface resulting in gloval warming. Copyright 2001 by Harcourt, Inc. All rights reserved. 1.33