Chapter 3. Matter and Energy

3.1 Three States of Matter: Gas Gas: Particles are far apart and are in constant motion. Chapter 3: Matter and Energy  Gases have no set shape, they assume shape of the container.  Gases have no set volume, it is variable  If volume increases, particles move farther apart.  If volume decreases, particles move closer together. Three States of Matter: Liquid, Solid Ways to Draw the States of Matter Liquid: Particles are close together but are free to flow around one another.  Liquids assume shape of the container.  Volume is constant (can’t compress). Solid: Particles are packed tightly together & organized in a rigid pattern; the atoms vibrate in place.  Solids have a definite, fixed shape.  Volume is constant. Cool animations States of Matter - interactive: 3.2 Definitions  Element – one type of atom only, can be single atoms (He) or diatomic molecules (O2), cannot be broken down further chemically  Compound – two or more different atoms bonded together, can be broken down chemically into elements  Pure – all particles are the same, cannot be physically separated  Mixture – two or more different particles mixed 3 States Of Matter – Scroll down and click on all the states of matter animations and the phase change animation (some may not work which is why there are several options) together, can be physically separated (top picture is pure element, bottom is pure compound) 1 This is how we draw atoms of an element 2 or more atoms bonded together = Molecules of an element, if same Molecules of a Compound, if different Examples •Mixtures • Metal alloys like 18-K gold, brass • Sand, granite, rocks • Tap water • Air which consists of nitrogen, oxygen, and other trace gases. •Pure • Salt (NaCl) is a compound • Diamond (C) is an element • Distilled water is a compound (H2O) • Mercury is an element (Hg) For each image, indicate if it represents 1) pure substance or mixture 2) atom, molecule, and/or compound element compound mixture 2 3.3 Elements Element Symbols and Names 1. Each element has a unique name, symbol, and atomic number 2. Capitalize the first letter of element name: hydrogen = H, carbon = C 3. If there’s a 2nd letter it is lower case: helium = He calcium = Ca cobalt = Co Some symbols are from English names: hydrogen=H; oxygen=O; Helium=He Some are from Latin names: lead Pb (plumbum) gold Au (aurum means “golden dawn”) Be careful! CO is carbon monoxide, Co is cobalt Periodic Table: You already know many of these Let’s name them! Know the Names and symbols of the first 20 elements of the Periodic Table and the following: Ag (silver) Au (gold) Pb (lead) Br (bromine) I (iodine) Hg (mercury) 3.4 Metals, Nonmetals, and Semimetals (Fig. 3.5) 1. Metals are on the left side of the stair-step line 2. Nonmetals (except H) are located on the right side of the stair-step line 3. Semimetals are touching the stair-step line following B (except Al which is metal) Properties of Metals vs. Nonmetals Metals Nonmetals shiny appearance dull appearance malleable, ductile Brittle solids All solids but Hg Many gases density – usually high density – usually low melting point - high melting point low Good conductors of Poor conductors (make heat & electricity better insulators) Semimetals (metalloids) Have properties in between 3 Physical states of the elements Physical States of the Elements at 25 ˚C and normal atmospheric pressure KNOW THESE: • Only mercury (Hg) and bromine (Br2) are liquids • H2, N2, O2, F2, Cl2, and all Noble gases (Group VIIIA) are gases • All other elements are solids Two Diatomic Elements Bromine Br2(l) and Iodine I2(s) 7 Diatomic elements Diatomic means two atoms bonded together Have no fear of ice cold beer! H2(g) N2(g) F2(g) O2(g) I2(s) Cl2(g) Br2 (l) Names and Properties of the Elements I should be able to point at any element and you tell me: 1. Name (for some of them) 2. Solid, liquid, or gas 3. Diatomic or not 4. Metal, semimetal, nonmetal Let’s play! I’ll point at several elements, and you identify the four properties above. 3.5 Compounds and Chemical Formulas • Formulas tell us: • Type of atoms = element symbols • Number of atoms = subscripts (1 is never written) • But NOT their bonding order water = H2O  2 H atoms, 1 O atom but the structure of water is not H-H-O Ex: How many atoms in potassium nitrate = KNO3 ___ K, ___ N, ___ O atoms but the structure is not K-N-O-O-O Ex: 4 Practice Problems 1) How many of each atom are in (NH4)3PO4? What is the total number of atoms? Chemical Formulas 2) How many atoms of each element are present in Viagra: C22H30N6O4S ? 3) How many atoms of each element are in lactic acid: CH3CHOHCOOH? Law of Definite Composition Compounds always contain the same elements in the same proportion by mass. Ex: Water, H2O, always contains 11.2 % H and 88.8 % O by mass whether you have a glass full, a swimming pool, or an ocean. Ex: Table salt, NaCl, is always 39.34% Na and 60.66% Cl ions by mass. 3.7 Physical and Chemical Changes Physical change: a change that keeps chemical composition the same, the molecules stay the same with the SAME formula. 3.6 Physical and Chemical Properties Physical: color, odor, taste, texture, melting point, physical state (s, l, or g), density, solubility, conductivity, hardness Chemical: describe how a substance reacts or behaves. (explosive, corrosive, toxic, inert, reactive, rusts, oxidizes, decomposes, etc.); We can only identify these when substances react with other substances!! Note that the H2O molecules remain H2O regardless of whether the sample is a solid, liquid, or gas; changes in physical state are physical changes. Structures/bonds do not break. Physical Changes ARE changes in state: (s  l  g) Ex: boiling water, melting gold, freezing alcohol, breaking glass, dissolving salt in water, and dry ice subliming 5 Physical Changes – learn these 6 terms Review Physical Changes – know these terms! Physical Changes • Atoms are always moving, even in solid state. Motion doesn’t stop until we reach 0 Kelvin (theoretically). • When you heat ice, the water particles gain kinetic energy and move faster. Chemical Changes: a process that changes the chemical composition, the molecules break apart and rearrange. The formula CHANGES. (aka chemical reactions) Starting substance is destroyed and a new substance with different properties is formed. • When particles gain enough energy to overcome attractive forces the solid will melt  liquid. • If we keep heating the liquid, the particles gain more KE & move even faster  gaseous state Ex: burning gas Chemical Reactions Indicators of chemical reaction: These may indicate chemical change  oxidation of matter (burning or rusting)  release of gas bubbles (fizzing) without heating REACTANTS  PRODUCTS Starting substances are called reactants; (thus not boiling)  formation of solid (precipitation)  release of heat or light  change in color or odor New substances formed are called products. Ex: 2 H2 + O2  2 H2O 6 Ex: Chemical reaction between sodium metal Na(s) and chlorine gas Cl2(g). They produce salt (NaCl) which is a totally different chemical with different formula and properties than the reactants. 3.9 Kinetic Energy - Energy of motion 3.8 Law of Conservation of Mass Matter or mass cannot be created or destroyed. What we start with is the same mass as what we end up with. mass of the reactant(s) = mass of the product(s) Two reactants make 4.0 grams of product. If one reactant was 1.5 grams, the other was ________. A + B  C 1.5 g + ___ = 4.0 g Potential Energy - Stored Energy Examples Examples • Water flowing over a dam • Water behind a dam • Working out • Gasoline or coal • Chemical bonds in food • Car at top of roller coaster • Dancing • Burning gasoline • Atoms moving KE, Temp, and physical state  As kinetic energy (KE) increases and molecules move and vibrate faster, the temperature ____________. As kinetic energy increases a solid will eventually turn into a ____________. And as the KE increases even more it will eventually turn into a ____________.  KE and T are related directly or indirectly? 3.10 Law of Conservation of Energy Energy cannot be created or destroyed, only converted from one form to another. Ex: When we digest food its stored energy (potential) is converted to kinetic energy to do work.  Which state of matter has lowest KE? Highest? 7 6 Other Forms of Energy • Radiant (light, UV, radiowaves, etc.) Chapter 3 Self Test Page 97 • Heat  Try # 1 – 2, 4 – 9, 13, 14 • Chemical (stored in bonds)  Answers in Appendix J • Electrical • Mechanical • Nuclear 8