Chemistry chapter 1 and chapter 2 study guide
Chemistry chapter 1 and chapter 2 study guide Chem 121
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This 11 page Study Guide was uploaded by Elisha Hanson on Tuesday January 26, 2016. The Study Guide belongs to Chem 121 at Eastern Michigan University taught by in Fall 2016. Since its upload, it has received 95 views. For similar materials see General Chemistry 1 in Chemistry at Eastern Michigan University.
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Date Created: 01/26/16
Chapter 2 Cathode Rays – Streams of electrons emitted by the cathode in a partially evaluated tube. Electrons – a subatomic particle that has a negative charge and essentially zero mass. Radioactivity – The spontaneous emission of high –energy radiation and particles by materials Beta Particles – a radioactive emission that is a high – energy electron Alpha particles – a radioactive emission with a charge of 2+ and a mass equivalent to that of a helium nucleus. Nucleus – (of an atom) the positively charged center of an atom that contains nearly all the atom’s mass. Proton – a positively charged subatomic particle present in the nucleus of an atom Neutron – an electrically neutral (uncharged) subatomic particle found in the nucleus of an atom. Atomic mass unit (amu) – unit used to express the relative masses of atoms and subatomic particles; it is exactly 1/12 the mass of one atom of carbon with six protons and six neutrons in is nucleus. Dalton (Da) – a unit of mass identical to 1 atomic mass unit. Ion – an atom or group of atoms that has a net positive or negative charge. Isotopes – atoms of an element containing different numbers of neutrons Nuclide – the nucleus of a specific isotopes of an element Atomic number (Z) – the number of protons in the nucleus of an atom Nucleon – either a proton or a neuron in a nucleus Mass number (A) – the number of nucleons in a atom Periodic table of the elements – a chart of the elements in order of their atomic numbers and in a pattern based on their physical and chemical properties. Average atomic mass – a weighted average of masses of all isotopes of an element, calculated by multiplying the natural abundance of each isotope by its mass in atomic mass units and then summing these products. Natural abundance – the proportion of a particular isotopes, usually expressed as a percentage, relative to all the isotopes of that element in a natural sample. Period – a horizontal row in the periodic table Group – all elements in the same column of the periodic table, also called family. Halogens – The elements in group 17 of the periodic table Alkali metals – the elements in group 1 of the periodic table Alkaline Earth metals – the elements in group 2 of the periodic table Metals – the elements on the left side of the periodic table that are typically shiny solids that conduct heat and electricity well and are malleable and ductile. Nonmetals – the elements with properties opposite those of metals, including poor conductivity of heat and electricity Metalloids – (also called semimetals) elements along the border between metals and nonmetals in the periodic table, they have some metallic and some nonmetallic properties Main group elements (also called representative elements) – in the groups 1,2 and 13 through 18 of the periodic table Transition metals – the elements in groups 3 through 12 of the periodic table Noble gasses – the elements in group 18 of the periodic table. Law of multiple proportions – the ratio of the two masses of one element that react with a given mass of another element to form two different compounds is the ratio of two small whole numbers Molecular compounds – a compound composed of atoms held together in molecules by covalent bonds Covalent bond – a bond between two atoms created by sharing one or more pairs of electrons Molecular formula – a notation showing the number and type of atoms present in one molecules of a molecular compound Ionic compound – a compound composed of positively and negatively charged ions held together by electrostatic attraction Cation – a positively charged particle created when an atom of molecule loses one or more electrons Anion – a negatively charged particle created when an atom or molecule gains one or more electrons Empirical formula – a formula showing the smallest whole – number ratio of elements in a compound Formula unit – the smallest electrically neutral unit of an ionic compound Polyatomic ions – charged groups of two or more atoms joined together by covalent bonds Oxo anions – polyatomic ions that contain oxygen in combinations with one or more other elements. Quarks – Elementary particles that combine to form neutrons and protons Nucleosynthesis – The natural formation of nuclei as a result of fusion and other nuclear processes Scientific method – method to acquire knowledge through observation and experimentation Chemistry – study of matter, its composition, structure and properties Mater – anything that occupies spaces and has mass. The stuff that all things are made of. Mass – defines the quantity of matter in an object Element – a pure substance that cannot be broken down into simpler substances by chemical or physical means Compounds – pure substances compose at two or more elements combined in definite proportions - Can be broken down into individual elements by chemical means Molecules – collection of atoms chemically bonded together in a characteristic patterns and properties -hydrogen and oxygen like several other elements that are gasses at room temperature, exists as diatomic (two-atoms) molecules and therefore are represented by the chemical formulas H2 and O2 Homogeneous – constituents are distributed uniformly throughout the sample Heterogeneous – individual in which the components are not distributes uniformly, so that the mixture contains distinct regions, of different compositions Classify matter Pure substances – some physical and chemical properties throughout - Cannot be separated into simpler substances by physical processes - Every particle is identical - 2 mixtures composed of two or more substances Physical properties – a property of a substance that can be observed without changing it into another substances Chemical properties – a property of a substance that can be observed only by reacting it to form another substances Intensive properties – a property that is independent of the amount of substance present Extensive property – a property that varies with the quantity of the substance present Know how particles are distributed in a solid, liquid, and gas? - Solid = define volume and shape - Liquid = define volume but not a definite shape - Gas = (or vapor) has neither a definite volume, nor a definite shape Know these metric prefixes - Kilo = k - Centi = C - Milli = m - Micro = um - 1kg = 2.205 lbs, 1lbs =0.4536kg =453.6g - 1g = 0.0357 ounce (oz), 1 oz = 28.35g - 1m=1.094yards 1yd =0.9144 (exactly) - 1m=39.37inches 1foot=0.3048m (exactly) - 1m=2.54cm (exactly) - 1km=0.6214 miles, 1mi=1.609km - 1m^3= 35.31ft^3, 1ft^3=0.02832m^3 - 1m^3=1000liters(exactly) - 1L=0.2642gallons, 1 gal=3.785L - 1L = 1.057guarts, 1qt=0.946L Precision – The extent to which repeated measurements of the same variable agree. Accuracy – agreement between an experimental value and the true value. Chemical bond – energy that holds two atoms in a molecule together Filtration – a process for separating particles suspended in a liquid or a gas from that liquid or gas by passing the mixture through a medium that retains the particles Distillation – a separation technique in which the more volatile (more easily vaporized) components of a mixture are vaporized and then condensed, thereby separating them from the less violate components. COAST – Collect and Organize, Analyze, Solve, Think About It Intensive property – a property that is independent of the amount of substance present Extensive property – a property that varies with the quantity of the substances present Physical property – a property of a substance that can be observed without changing it into another substance Density (d)- the ratio of the mass (m) of an object to its volume (v) Chemical property – a property of a substances that can be observed only by reacting it to form another substance Solid – a form of matter that has a definite shape and volume Liquid - a form of matter that occupies a definite volume but flows to assume the shape of its container Gas – a form or matter that has neither definite volume nor shape and that expands to fill its containers, also called vapor. Sublimation – transformation of a solid directly into a vapor (gas) Deposition – transformation of a vapor (gas) directly into a solid Meter – the standard unit of length, named after the Greek matron, which means “measure” and equivalent to 39.57 inches. Significant figures – all the certain digits in a measured value plus one estimated digit. The greater the number of significant figures, the greater the certainly with which the value is known. Conversion factor – a fraction in which the numerator is equivalent to the denominator but, is expressed in different units, making the value of the fraction one. Temperature scales - Fahrenheit scale is rarely used in scientific work. - Temperature is the kelvin (K) - Kelvin scale is not related to the freezing of a particular substance rather; it is the coldest temperature called absolute zero (0K) - Kelvin scale differs from that on the Celsius scale the size of 1 degree is the same on the two scales. The Big Bang: scientific Theory Georges – Henri Lemaitre (1972) - All matter in the universe created during a huge, instantaneous release of energy, resulting in expanding universe. Hypothesized from the observation that all the galaxies in the universe are moving away from the milky way and one another. Einstein’s formula E=Mc^2 (1905) Edwin Powell Hubble - Observed “shift” in light emitted by distant stars supported by the theory Robert Dickel (1960s) - Predicted that residual energy from the big bang could be measured as microwave energy. Robert W. Wilson and Arno A. Penzias of Bell Laboratories (1978) - Shared Nobel prize in physics for discovery of cosmic microwave background radiation of the universe The scientific method Sir Francis Bacon 1561-1626: scientific method - Method to acquire knowledge through observation and experimentation 1.2 Matter: An Atomic View Atom – smallest representative particle of an element Silicon – limit is one atom of silicon Chemists view – matter and its properties on the atomic level, which is also called the microscopic or particulate level Chemical formula – consist of the symbols of elements and subscripts that indicate the number of atoms of each element in the molecule. Chemical equation – chemical formulas represent the identities of substances involved in a chemical reaction - Provide information about the proportions of the elements in a compound, but they do not tell us how the atoms of those elements are connected in a molecule of the compound, or talk about the shapes of the molecules. Measurements – essential for characterizing physical and chemical properties of matter. - Two parts of every measurement: o Numbers and units - Standardization of the units of measurement is essential Unit conversion factor - A fraction in which the numerator and denominator represent equivalent quantities but expressed in different units. Dimensional analysis - Units cancel - Always label units - If don’t label could put things in the wrong order - Check units first before using a calculator - Factor of 1, just because changing the units doesn’t mean were changing the other numbers Exact – numbers with defined values Examples – counting numbers, conversion factors based on definitions Inexact – numbers obtained by any method other than counting Uncertainty in measurements - All measurements contain uncertainty - Amounts of uncertainty depends on instruments used to make the measurement - A digit that must be estimated is called uncertain (last recorded digits) Guide lines for determine significant figures - Any non-zero digits is significant: 897988 (6 sig. figs) - Zeros between non-zero digits are significant: 1001 (4 sig. figs) - Zeros to the left of the first non-zero digit are not significant: 0.00078 (2 sigs.figs.) - Zeros to the right of the last non-zero digits are significant if decimal is present: 1002.890890 (10 sig.fig) - Zeros to the right of the last non-zero digits are not significant if decimal is not present: 9800 (2 sig.fig) Rounding off - Drop “insignificant” digits - If the portion to be dropped is: <5, no change,>5 Increases - 5 exactly then round to the nearest even digit Precision can be increased by mathematical operations - “weakest link” principle - The number of significant figures in the final results cannot be greater than the “weakest link” used in the calculations. - The actual rule depends on the mathematical operation Calculations with measured numbers - Addition and subtraction - Answers cannot have more digits to the right of the decimal than any of original numbers Atoms and Ions and molecules: matter starts here Timeline of the beginning - Existence of subatomic particles - Subatomic particles fuse to form H and He nucleic - H and He atoms in stars fuse to elements Large Hadron Collider: World’s largest particle accelerator - Circular tunnel 17 miles in diameter - 574 feet below switcher land Historical Perspective - 400 Bc. The Greek philopher Democritus proposed that matter was made of indestructible particles called atoms - Mid 1800s it became evident that atoms are divisible - There is and internal atom J.J Thompson 1897 - beam from cathode ray tube is deflected by a magnetic field – indicates mass is present. - the cathode ray is deflected away from the negative plate by an electric field, thus the particles are charged - Thompson calculated the charges/mass ratio of the particles called electrons Mass of an electron Robert Millikan 1909 - Determined the mass and charge of an electron with his oil – drop experiment Thompson’s model of the Atom Plum-pudding model: - Electrons distributed throughout diffused, positively charged atom Henri Becquerel (1896) - Some material produces invisible radiation consisting of charged Ruthard’s experiment Orange = region of diffused positive - Charged (b) - Blue = diffused One problem: - If H has a mass of 1 - Then he should have a mass of 2 but its mass is 4! 1932 James Chadwick - Discovered the neutron - Third subatomic particle - Neutral charged - Bombarded beryllium with a particle and observed non-charged particels The number Atoms The nucleus - Positively charged center of atoms, containing nearly all of the atoms mass - 1/10,000 the size of the atom - Consists of two types of particles Atomic mass units - Atomic mass units (amu) - Relative scale to express the masses of atoms and subatomic particles Atomic number = (z) = number of protons The chemical identity of an atom can be determined solely from its atomic number The atomic number defined an element - Also indicates the number of electrons in an atom since atoms are neutral Mass # (A) = total (number of neutrons and protons) The nucleus Mass # (A) = # of protons (z) + number of neutrons Standard notation - mass number - (number of protons + neutrons) Aston’s Experiment - Positive –ray analyze results o Two different kinds of neon gas atoms exist o 90% = 20 amu o 10% = 22 amu - Aston proposed theory of isotopes Isotopes - Atoms of an element containing the same number of protons but different numbers of neutrons - All atoms of an element are not identical - Isotopes all have the same atomic numbers - (z) but different mass number (a) - (varies numbers of neutrons) - Examples: isotopes of hydrogen - Hydrogen (protrium, 99.98%) - Deuterium (0.002%) 2/1H Average atomic masses - Weighted average of a neutral sample of an element - Calculated by multiplying the natural abundance of each isotope by its exact mass in amu and then summing these products Weighted average example - Neon has three naturally occurring isotopes - Average atomic mass of neon 20.1797 amu
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