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UCM CHEM 1131 - Exam 1 Study Guide

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Chem 1131 1st EditionExam # 1 Study Guide Chapters 1,2Chapter 1The key components of the scientific method1. Collecting data by observation: the act of making and recording a measurement. It should be objective, unbiased and repeatable. 2. Identify patterns and trends in the data3. Summarize into law - a mathematical statement of a reliable relationship between phenomena. 4. Formulate a hypothesis – a testable explanation of observable phenomenon.* When a hypothesis stands the test of extensive experimentation, it evolves into a theory – a unifying principle. States of matterMixture MatterMixture:A physical combination of twoor more substancesHomogeneous:Evenly dispersede.g. seawater, applejuiceHeterogeneous (impure):Not evenly dispersede.g. trail mix, chicken soup*Solution: same phase *Suspension: different phaseProperties of matterQuantitative properties: measure and expressed with a number in the english and metric system.Qualitative properties: do not require measurement and are usually based on observation.Physical property: can be observed or measured without changing the indentity.Physical change: change of the state of matterSubstanceA form of matter that has definite composition and distinct properties; differ in composition E.g. iron,water,mercuryShape Volume solid Definite Definite liquid Indefinite Definitegas Indefinite IndefiniteChemical property: substance exhibits as it interact with another substanceChemical change: change of composition and bonding of the atoms – chemical identity.e.g. digestion, oxidation. Extensive property: depends on the amount of matter. e.g. mass/volumeIntensive property: does not depend on the amount of matter. E.g. temperature/densitySI Units and prefixPhysical quantity Unit AbbreviationMass Kilogram kgLength Meter mTime Second sTemperature Kelvin KAmount of substance Mole molElectric current Ampere ALuminous intensity Candela cdTemperature FormulaDerived Unit: Volume and DensityDerived unit for volume: m31d m3 = 1L 1cm3=1mLThe density of a substance is the ratio of mass to volume; d=mvSignificant figure rules1. Any nonzero digit is significant. e.g. 155.8 (4 sig fig)2. Zeros between nonzero digits are significant. e.g. 809 (3)3. Zeros to the left of the first nonzero digit are not significant. e.g. 0.098 (2)4. Zeros to the right of the last nonzero digit are significant if a decimal is present. e.g. 4.500 (4)℃ =(℉ +32)∗59℉=(95℃ +32)K=(℃ +273)prefix factor prefix factortera1012centi10−2giga109mili10−3mega106micro10−6kilo103nano10−9hecto102pico10−12deka101femoto10−15deci10−15. Zeros to the right of the last nonzero digit in a number that does not contain a decimal point may or may not be significant. e.g. 500 (1,2 or 3)Accuracy and PrecisionAccuracy: How close a measurement is to the true or accepted value.Precision: How close a series of replicate measurement are to one another.Conversion FactorsConversion factor: a fraction in which the same quantity which can be expressed by exchanging the numerator and the denominator.e.g. 3ft = 1yd can be written: 1 yd3 ft∨3 ft1 yd ; Converting 9ft to yard: 9ft∗1 yd3 ft = 3ftScientific Notation 478,000 = 4.78 * 105 ¿ positive if you moved to the left5 spaces to left 0.00897 = 8.97 * 10−3<¿ negative if you moved to the right3 spaces to rightChapter 2Atom and ElementAtom: the smallest quantity of matter that still retains the properties of matter.Element: a substance that cannot be broken down into two or more simpler substances by any means.e.g. gold, sodium, silverSubatomic particle: particles that can be obtained by dividing a single atom – proton, electron and neutronImportant ExperimentsJ.J Thomson: He used magnetic and electric fields to measure the mass to charge ratio of a cathode ray particle. He noted that the rays in the cathode ray tube were composed of negatively charged particles – electronsR.A. Millikan: He determined the charge on an electron by examining the motion of tiny oil drops.Wilhelm Rontgen: discovered X-rays. They were not deflected by magnetic or electric fields, so they could not consist of charged particles.move decimal point to arrive at a number between 1 and 10, which is 4.78Move decimal point to arrive at a number between 1 and 10, which is 8.97Antoine Becquerel: discovered radioactivity, the spontaneous emission of radiationErnest Rutherford: His gold foil experiment is important because it clearly demonstrated that the atom is mostly empty space. Rutherford’s results also showed that most of the atom’s mass is located in the nucleus, which has a very small volume. Types of RadiationRadioactive substances, such as uranium, can produce three types of radiation.Alpha (α) rays +2 : consist of positively charged particles, called α particles.Beta (β) rays -1: they are electrons so they are deflected away from the negatively charged plate.Gamma (γ) rays: they have no charge like x-rays and are unaffected by external electric or magnetic fields.Electrons, protons, and NeutronsProtons: positively charged particles found in the nucleus. They determine the identity of an element. For instance, nitrogen’s atomic number is 7, so every nitrogen has 7 protons. Mass – 1.67262 * 10−24Neutrons: electronically neutral particles found in the nucleus. Neutrons are slightly larger than protons. Mass – 1.67493 * 10−24Electron: a negatively charged subatomic particle that orbit around the nucleus. Mass – 9.10938 *10−28Atomic Number, Mass Number, and IsotopesThe atomic number (Z): the number of protons in the nucleus. Number of electrons are same as Atoms are neutral, so number of protons is the same as the number of electrons.The mass number (A): the total number of protons and neutrons.Isotope: atoms that have the same atomic number (Z) but different mass number (A)Isotope of the same elements has similar chemical properties and the same number of protons and electrons. e.g. The Weighted Average of Atomic MassAtomic mass: the mass of an atom in atomic mass units (amu).1 amu = 1/12 the mass of a carbon-12 atomThe weighted average atomic mass: the average mass of the naturally occurring mixture of isotopes.e.g. Isotope : C-12 ; 12.00000 (amu) ; 98.93% (natural abundance) C-13 ; 13.003355 (amu) ; 1.07% (natural abundance) AZ X← element symbol1 H 3 21 H1 proton, 2 neutrons 1 proton, 1 neutronWeighted Average mass (C) =


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