CHM2045 Ch 2 Notes
CHM2045 Ch 2 Notes CHM 2045
Popular in Freshman Chemistry 1
Popular in Chemistry
This 5 page Class Notes was uploaded by Daniel Donovan on Wednesday September 14, 2016. The Class Notes belongs to CHM 2045 at University of Florida taught by Dr. Martina Sumner in Fall 2016. Since its upload, it has received 71 views. For similar materials see Freshman Chemistry 1 in Chemistry at University of Florida.
Reviews for CHM2045 Ch 2 Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 09/14/16
Ch. 2 The Components of Matter 2.1 Elements, Compounds, and Mixtures: An atomic overview Element: substance that cannot be decomposed into simpler substances by chemical. Ex. Chlorine cannot be decomposed into other “smaller” elements Compound: consists of two or more different elements that are bonded chemically; this CAN be decomposed into simpler substance but must always have the same mass. Ex. H 2 can be broken down into the two elements hydrogen and oxygen. Mixture: a combination of 2 or more pure substances in which each substance retains its own composition and properties: THERE ARE TWO TYPES OF MIXTURES: Heterogeneous: does not have uniform composition and properties throughout. o Ex. Oil and water Homogeneous: called a solution because of the uniformity of composition and properties. o Ex. Sugar and water All matter consists as either elements, compounds or mixtures. 2.2 The Observations that led to an atomic view of Matter Law of Mass Conservation: The total mass of substances does not change during a chemical reaction. o Ex. 180 g glucose + 192 g oxygen gas -> 264 g carbon dioxide + 108 g water 372 g material before -> 372 g material after. MATTER CANNOT BE CREATED OR DESTROYED Law of definite (or constant) composition: No matter what its source, a particular compound is composed of the same elements in the same parts (fractions) by mass. o Ex. Ca 2O 4 Fraction by mass (mass fraction) – part of the compound’s mass that each element contributes. o Ex. Mass Fraction (parts/1.00 part) = 0.40 Ca, 0.12 carbon, 0.48 oxygen Percent by mass (mass percent, mass %) – the fraction by mass expressed as a percentage (%) o Ex. Mass Percent (parts/100 parts) = 40 % Ca, 12% C, 48% oxygen Mass of element in sample = mass of compound in sample *(mass of element / mass of compound) Law of Multiple Proportions: if elements A and B react to form two compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers. Ex. Carbon oxide I is 57.1 mass % oxygen and 42.9 mass % carbon Carbon oxide II is 72.7 mass % oxygen and 27.3 mass % carbon. Carbon oxide I: Carbon oxide II G oxygen/100 g compound 57.1 72.7 G carbon/100 g compound 42.9 27.3 G oxygen / g carbon 57.1/42.9 = 1.33 72.7/27.3 = 2.66 Divide the grams of oxygen per gram of carbon II by that in I, we obtain a ratio of small numbers: (2.66 g oxygen/g carbon in II)/ (1.33 g oxygen/g carbon in I) = 2/1 o This tells us that for a given mass of carbon, compound II contains 2 times as much oxygen as I. 2.3 Dalton’s Atomic Theory KNOW THESE! 1. All matter consists of atoms, tiny divisible particles of an element that cannot be created nor destroyed. 2. Atoms of one element cannot be converted into atoms of another element. Instead they recombine to form different substances. 3. Atoms of an element are identical in mass and other properties are different from atoms of any other element. a. Unique mass and properties for the atoms of a given element. 4. Compounds result from the chemical combinations of a specific ratio of atoms of different elements. 2.4 The Observations that Led to the Nuclear Atom Model. Know about the many different experiments i.e watch the short videos. 2.5 The Atomic Theory Today Atom: an electrically neutral, spherical entity composed of a positively charged central nucleus surrounded by one or more negatively charged electrons. Properties of the Subatomic Particles: + Proton(p ): has a positive 1 charge and weighs relative 1 g/mol 0 Neutron(N ): has a neutral, or no, charge and weighs relatively 1 g/mol - Electron (e ): -1 charge, mass about 0 g/mol The Atomic Number(Z): equals the number of protons in the nucleus of each of its atoms. o Ex. All carbon atoms (Z=6) have 6 protons. The mass number(A): the total number of protons and neutrons in the nucleus. o Ex. A carbon atom with 6 protons and 6 neutrons will have a mass number of 12. The Atomic (or element symbol): based on its English, Latin, or Greek name such as C for Carbon, and S for Sulfur. Number of Neutrons = mass number – atomic number or N= A – Z. Isotopes: atoms that have different numbers of neutrons and therefore different mass numbers. Isotope Abundance: Atomic Weight = (% abundance isotope 1 / 100)*(mass of isotope 1)+ (% abundance isotope 2 / 100)* (mass of isotope 2) + … o The atomic weight of the element is always closer to the mass of the most abundant isotope or isotopes. 2.6 Elements: A First Look at the Periodic Table Most important tool used by chemists o Contains information about each element o Organizes elements according to chemical and physical properties. Need to know the 7 diatomic elements: H2, N2, O2, F2, Cl2, Br2, I2 Groups: o Vertical columns o Elements have similar chemical and physical properties o There are 18 groups in the periodic table Periods o Represent trends o Periodic trends are changes that occur from left to right o There are seven periods in the table 2.7 Compounds: Introduction to bonding: Cation: + charged ion Anion: - charged ion FUN WAY TO REMEMBER THE DIFFERENCE: A cation is “paws”itive Ionic compounds are neutral because they contain an equal number of positive and negative charges. Forming Cations and Anions Cation: each metal loses one or more electrons Anion: Each nonmetal atoms gains one or more of the electrons lost by the metal atom and becomes negatively charged. Coulomb’s Law: the energy or attraction or repulsion between 2 particles is directly proportional to the product of the charges and inversely proportional to the distance between them. Energy = (charge 1 * charge 2 ) / distance Naming Ionic Compounds o Cation is named first and anion is named second The formation of covalent compounds o Covalent compounds consists of different elements held together by covalent bonds. o Formed by 2 or more nonmetals o Shares electrons Naming Covalent compounds Have to know prefixes 1- Mono 6. Hexa 2- Di 7. Hepta 3- Tri 8. Octa 4- Tetra 9. Nona 5- Penta 10 deca Examples: SO3 = sulfur trioxide P4O6 = tetraphosphorus hexaoxide Hydrocarbons: Binary nonmetal compounds containing only C and H o Given special names o One class of organic compounds o Named according to number of C and H atoms in the formula o Ex. Methane (CH4), Ethane (C2H6), Propane (C3H8) Inorganic acids Produce H+ when dissolved in water Named as binary nonmetal compounds - Oxoacids: Groups of acids that differ only in the number of Oxygen atoms. 1 – Hypo 2. -ous 3 -ic 4.Per – ic Ex. HClO4 = Perchloric acid Representing Molecules with Formulas and Models Molecular Formula: symbol for each element and subscript number to identify how many atoms of each element. Empirical formulas: the simplest whole number ratio of elements in a compound (CH (C6H6)) Structural formulas: shows the connections
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'