Real Science-4-Kids Level I Rebecca W. Keller, Ph.D.
Cover design: Opening page: Illustrations: David Keller David Keller Rebecca W. Keller, Ph.D. Copyright 2004, 2005, 2007, 2008, 2009, 2010 Gravitas Publications, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. No part of this book may be used or reproduced in any manner whatsoever without written permission This publication may be photocopied without permission from the publisher only if the copies are to be used for teaching purposes within a family.. Real Science-4-Kids: Chemistry Level I Textbook ISBN # 0-9749149-0-8 Published by Gravitas Publications, Inc. 4116 Jackie Road SE, Suite 101 Rio Rancho, NM 87124 www.gravitaspublications.com Illustrations Chapter 9, 9.1: Art Today Chapter 10: All molecular coordinates were provided by the Brookhaven Protein Data Bank. Front cover: water molecule showing both the bonding of two hydrogens to one oxygen and the van der Waals radii of the atoms Back cover, inside title page: L-alanine molecule one of the amino acids Special thanks to Susan Searles for copyediting and review of the manuscript. Also, I d like to thank the Keller kids (Kimberly, Chris, and Katy), the Chesebrough kids (Sam and Ben), and the Megill kids (Lorien, Lee, Joshua, and Joseph) for critical evaluation of the text. Finally, I d like to thank Lina and Lillian McEwan for valuable input.
CONTENTS iii Contents CHAPTER 1: MATTER 1 1.1 Introduction 2 1.2 Atoms 2 1.3 Periodic table 4 1.4 Summary 7 CHAPTER 2: MOLECULES 8 2.1 From atoms to molecules 9 2.2 Forming bonds 9 2.3 Types of bonds 10 2.4 Shared electron bonds 10 2.5 Unshared electron bonds 11 2.6 Bonding rules 11 2.7 Shapes of molecules 12 2.8 Summary 13 CHAPTER 3: CHEMICAL REACTIONS 14 3.1 Introduction 15 3.2 Combination reaction 15 3.3 Decomposition reaction 16 3.4 Displacement reaction 16 3.5 Exchange reaction 17 3.6 Spontaneous or not? 17 3.7 Evidences of chemical reactions 18 3.8 Summary 19 CHAPTER 4: ACIDS, BASES, AND ph 20 4.1 Introduction 21 4.2 The ph scale 21 4.3 Properties of acids and bases 22 4.4 Measuring ph 23 4.5 Summary 24 CHAPTER 5: Acid-Base NEUTRALIZATION 25 5.1 Introduction 26 5.2 Concentration 27 5.3 Titration 28 5.4 Plotting data 29 5.5 Plot of an acid-base titration 30 5.6 Summary 31
iv CONTENTS CHAPTER 6: MIXTURES 32 6.1 Introduction 33 6.2 Types of mixtures 34 6.3 Like dissolves like 35 6.4 Soap 38 6.5 Summary 39 CHAPTER 7: SEPARATING MIXTURES 40 7.1 Introduction 41 7.2 Filtration 41 7.3 Evaporation 41 7.4 Solids, liquids, and gases 42 7.5 Chromatography 43 7.6 Summary 44 CHAPTER 8: ENERGY MOLECULES 45 8.1 Introduction 46 8.2 Nutrients 46 8.3 Carbohydrates 47 8.4 Starches 48 8.5 Cellulose 49 8.6 Summary 50 CHAPTER 9: POLYMERS 51 9.1 Introduction 52 9.2 Polymer uses 52 9.3 Structure of polymers 53 9.4 Modifying polymers 54 9.5 Summary 55 CHAPTER 10: BIOLOGICAL POLYMERS: Proteins and DNA 56 10.1 Introduction 57 10.2 Proteins 57 10.3 Proteins are amino acid polymers 58 10.4 Proteins form special shapes 58 10.5 Protein machines 60 10.6 DNA 62 10.7 DNA structure 63 10.8 Protein machines on DNA 64 10.9 Summary 64 Glossary Index 65
3 H Hydrogen 1.0079 Li Lithium 6.941 4 Be Beryllium 9.0122 The Periodic Table of Elements Noble gases 5 B Boron 10.811 6 C Carbon 12.011 7 N Nitrogen 14.0067 8 O Oxygen 15.9994 9 F Fluorine 18.9984 2 10 He Helium 1 Alkali metals Alkaline earth metals Metals Non-metals Metalloids Synthetic elements (unconfirmed) Halogens 4.003 Ne Neon F 20.1797 Na Sodium 22.9898 11 12 Mg Magnesium 24.3050 Transition metals 13 14 15 16 Al Aluminum 26.9815 Si Silicon 28.0855 P Phosphorus 30.9738 S Sulfur 32.066 17 Cl Chlorine 35.4527 18 Ar Argon 39.948 19 20 K Potassium 39.0983 Ca Calcium 40.078 21 Sc Scandium 44.9559 22 Ti Titanium 47.867 23 V Vanadium 50.9415 24 Cr Chromium 51.9961 25 Mn Manganese 54.9380 26 Fe Iron 55.847 27 Co Cobalt 58.9332 28 Ni Nickel 58.693 29 Cu Copper 63.546 30 Zn Zinc 65.38 Ga Gallium 69.723 32 33 34 32 Ge As Germanium Arsenic 72.64 74.9216 Se Selenium 78.96 35 35 Br Bromine 79.904 36 Kr Krypton 83.80 37 Rb Rubidium 85.4678 38 Sr Strontium 87.62 39 Y Yttrium 88.9059 40 Zr Zirconium 91.224 41 Nb Niobium 92.9064 42 Mo Molybdenum 95.96 43 Tc Technetium (98) 44 Ru Ruthenium 101.07 45 Rh Rhodium 102.9055 46 Pd Palladium 106.42 47 48 Ag Silver 107.8682 Cd Cadmium 112.411 49 In Indium 114.82 50 Sn Tin 118.710 51 52 Sb Antimony 121.757 Te Tellurium 127.60 53 I Iodine 126.9045 54 Xe Xenon 131.29 55 Cs Cesium 132.9054 56 Ba Barium 137.327 57 *La Lanthanum 138.9055 72 Hf Hafnium 178.49 73 Ta Tantalum 180.9479 74 W Tungsten 183.84 75 Re Rhenium 186.207 76 Os Osmium 190.2 77 Ir Iridium 192.22 78 Pt Platinum 195.08 79 Au Gold 196.9666 80 Hg Mercury 200.59 81 Tl Thallium 204.3833 82 Pb Lead 207.2 83 Bi Bismuth 208.9804 84 Po Polonium (209) 85 At Astatine (210) 86 Rn Radon (222) 87 Fr Francium (223) 88 Ra Radium 226.0254 89 **Ac Actinium 227.0278 104 Rf Rutherfordium 261 105 Db Dubnium 262.11 106 Sg Seaborgium 263 107 Bh Bohrium 264.12 108 Hs Hassium 269.13 109 Mt Meitnerium 266 110 Ds Darmstadtium (269) 111 Rg Roentgenium (272) 112 Cp Copernicum (277) 113 114 115 116 Uuq Ununtrium Ununquadium Ununpentium (284) (285) (288) Uut Uup Uuh Ununhexium (289) 117 118 Uus Ununseptium Uuo Ununoctium (293) *The lanthinide series: Elements 58-71 58 59 Ce Pr Cerium Praseodymium 140.116 140.9076 60 61 62 63 64 65 66 67 68 Nd Neodymium 144.24 Pm Promethium (145) Sm Samarium 150.36 Eu Europium 151.964 Gd Gadolinium 157.25 Tb Terbium 158.9253 Dy Dysprosium 162.50 Ho Holmium 164.9303 Er Erbium 167.26 69 Tm Thulium 168.9342 70 Yb Ytterbium 173.054 71 32 Lu Lutetium 174.967 **The actinide series: Elements 90-103 90 91 Th Pa Thorium Protactinium 232.0381 231.0359 92 93 94 95 96 97 98 99 100 U Uranium 238.0289 Np Neptunium 237.0482 Pu Plutonium (244) Am Americium (243) Cm Curium (247) Bk Berkelium (247) Cf Californium (251) Es Einsteinium (252) Fm Fermium (257) 101 Md Mendelevium (258) 102 No Nobelium (259) 103 32 Lr Lawrencium (260) http://www.gravitaspublications.com 31
CHEMISTRY LEVEL I
2 CHEMISTRY LEVEL I 1.1 Introduction What is chemistry? Have you ever wondered what the world and the objects in the world are made of? What is water exactly? Why do ice cubes float? What are our hair and skin made of? Why is a marble hard but a jellyfish soft? All of these questions, and others like them, begin the inquiry into that branch of science called chemistry. Chemistry is the study of matter which is a general term for what forms all living and nonliving things. Chemistry is concerned mainly with the properties of matter. All of the items we encounter on a daily basis are made of matter. Balloons are made of matter. Pancakes are made of matter. Baseballs are made of matter. Even our bodies are made of matter. But what makes up matter? 1.2 Atoms The fundamental building blocks of matter are atoms (a -tǝms). The word atom comes from the Greek word atomos, which means uncuttable. During the 5th century b.c., the Greek philosophers proposed the idea that there must be some smallest uncuttable units of matter. They called these units atoms.
CHAPTER 1: MATTER 3 Today we know that atoms are composed of even smaller particles called protons (prō -tänz), neutrons (nü -tränz ), and electrons (i-lek -tränz). Protons and neutrons are roughly equal in size, but electrons are very much smaller than both protons and neutrons. Protons, neutrons, and electrons are all much smaller than an atom. Protons and neutrons combine to form the central core or nucleus (nü klē ǝs) of an atom. The electrons occupy the space surrounding the nucleus. This space is sometimes called the electron cloud. The number of electrons in an atom always equals the number of protons. Notice that in the helium (hē -lē um) atom there are two protons and two electrons. Sometimes the number of protons also equals the number of neutrons, as with helium, but this is not always true. Most of the space of an atom is actually filled up by the electron cloud. The central core of an atom takes up only a very small part of the total space. On the other hand, almost all of the mass of the atom is in the protons and neutrons in the nucleus. The electrons weigh almost nothing compared to the nucleus, yet they take up all the space!
4 CHEMISTRY LEVEL I 1.3 Periodic table All of the atoms that make up the world are known. They are called chemical elements or just elements (e -lǝ-mǝnts). Early in the 19th century, a total of 55 chemical elements were known, and many more were being discovered. Their properties were very different from each other, and it was difficult to organize them. In 1867, Dmitri Mendeleev (dmē -trē men-dǝ-lā -ǝf) organized the elements into what is now called the periodic table of elements. In today s periodic table, the elements are arranged horizontally from left to right in order of increasing atomic number. The atomic number is the number of protons in the nucleus of each atom. For example, carbon has an atomic number of 6, which means it has 6 protons in its nucleus. Oxygen (äk -si-jǝn) has an atomic number of 8, which means it has 8 protons in its nucleus. All of the elements have a symbol. For example, hydrogen (hī -drǝ-jǝn) has the symbol H, and carbon has the symbol C. Notice that for these elements the symbol is the same as the first letter of the name. This is true for many elements because they have English names, like oxygen which has the symbol O. But some names come from other languages. The name for sodium (sō -dē-ǝm) comes from the Latin word natrium, so it has the symbol Na. Tungsten comes from the German word wolfram, so it has the symbol W. Other examples include gold, which has the symbol Au from the Latin word aurum, and lead (led), which has the symbol Pb from the Latin word plumbum.
CHAPTER 1: MATTER 5 As we just saw, the atomic number tells how many protons the atom contains. In an atom, the number of protons equals the number of electrons, so this number is also the number of electrons in an atom. For example, the smallest element is hydrogen. It has an atomic number of 1, which means it has only one proton. It also has only one electron, since the number of protons equals the number of electrons. Though atoms are very small, each one has a weight called the atomic weight. For most atoms the atomic weight is very close to the sum of the protons and neutrons in the nucleus. Both protons and neutrons have an atomic weight of 1. Electrons are so small that they are given almost no weight at all. The number of neutrons for an atom can be calculated by subtracting the number of protons from the atomic weight. For example, the atomic weight of hydrogen is 1.0079, which is the number found below the name. To find the number of neutrons, the number of protons (1) is subtracted from the atomic weight (1.0079 or 1); 1-1 = 0. This means that hydrogen has no neutrons and only one proton in its nucleus. The largest naturally occurring element is uranium (yü rā nē ǝm). It has an atomic number of 92, which means it has 92 protons and 92 electrons. It has an atomic weight of 238.0289. To calculate the number of neutrons, the number of protons is subtracted from the atomic weight (238-92 = 146), so uranium has 146 neutrons.
6 CHEMISTRY LEVEL I The elements in the periodic table are arranged vertically according to their chemical properties. All of the elements in a single column undergo similar chemical reactions and have similar chemical properties. All of the elements in the far right-hand column are called the noble gases. They are similar to each other because they don t react with other atoms or molecules. The elements in the far left-hand column are called the alkali (al -kǝ-lī) metals. They are similar to each other because they react with lots of different atoms or molecules. The periodic table of elements organizes a lot of information about the elements and their chemical properties. This table helps chemists predict the behavior of the elements and how they might interact with each other. Before all of the naturally occurring elements were known, Mendeleev used the organization of his table to predict many of the properties of the missing elements. The success of his predictions and the organization of his chart led to its acceptance as a major scientific accomplishment.
1.4 Summary CHAPTER 1: MATTER 7 Here are the most important points to remember from this chapter: All things, both living and nonliving, are made of atoms. Atoms are made of protons, neutrons, and electrons. In an atom, the number of protons equals the number of electrons. All atoms (or elements) are found in the periodic table of elements. The elements are arranged in the periodic table in groups that are similar.