## Chemistry

 Chemistry
 The study of composition, structure and properties of matter, the changes in which matter undergoes and the energy accompanying these changes.
 Sysem Internation
 scientific unit of measuremeter –> lengthKelvin –> temperature moles –> number of particlesLiter –> volume Amperes –> electric currentpascal –> pressurejoule –> heatgram –> mass
 Matter
 anything that has mass and occupies volume
 Mass
 the amount of matter an object contains
 Weight
 the force with which gravity attracts matter (not the same as mass)
 Volume
 the amount of three dimensional space an object occupies
 Temperature
 Measures the average kinetic energy
 Significant figures
 Number of digits that you report in the answer of a measurement you are taking or a problem you are solving
 Captive Zeros
 zeroes that are located between nonzero digits are always significant e.g. 1,004 4 sigfigs
 Leading Zeroes
 zeroes located before other numbers are not significant e.g. 0.000005 1 sigfig
 Trailing zeroes
 zeroes located after the last non-zero digit sometimes significant e.g. 32,000. 5 sigfigs because it has a decimal point at the end of it, if it did not it would only have 2 sigfigs
 Multiplying and dividing with Significant Figures
 1. Find the number with the least number of significant figures2. Round your answer to the least number of significant figuresexample: 2.35×3.845×8.9=80.418175 cm^3only two significant figures 80. is what you should report
 Addiction and Subtractions for Significant Figures
 1. Find the number with the least number of decimal places2. Round your answer to the least number of decimal placesexample: 2.35+3.845+8.9= 15.095the smallest decimal place is the tenths so the answer would be 15.0
 Dimensional Analysis
 A technique used to convert(or change) units1. Determine the unit equality2. Write down the given quantity 3. Determine the proper conversion factor4. Set-up and solveexample: how many inches are in 37.84 feet?37.84 feet x 12 inches equals 454.08 inches but 1 1 foot in sigfigs it is only 454.1
 Accuracy
 A measure of how close something is to that true value
 Precision
 a measure of measurements to each other
 Precent error (Located on the back of the Reference Tables)
 accepted-calculated x 100 accepted
 Particle
 a unit of matter
 Atom
 The smallest particle of an element that retains the properties of that element (ALWAYS NEUTRAL)
 Molecule
 The smallest particle of a compound that retains the properties of that compound
 Solids
 Particles are in an ordered geometric arrangement, they have definite shape and volume and the particles are very close together but are in constant motionl ll oo ll oo l
 Liquids
 Particles are in free motion, very close together and take the shape of the containerl l looolloool
 Gases
 Particles have free random motion and are usually far apartl o o llo o oll o o l
 Diffusion
 Movement of on substance through another high to low
 Compression
 decreased distance between atoms
 Physical Properties
 Can be measured and/or observed without changing the identity or composition of a substance. e.g. color, odor, density, melting/boiling point
 Extensive Properties
 Physical properties that depend on the amount of matter e.g. Mass and volume
 Intensive properties
 Physical properties that do not depend on the amount of matter e.g. Color, luster and density
 Chemical Properties
 Properties that lead to changes in the identity or composition of a substance e.g. Flammability, and ability to rust or oxidize
 Physical Change
 Changes in which the identity and composition of matter are not altered e.g. Physical Changes
 Chemical Changes
 Changes in which the identity and composition of matter are altered; new substances are made as a result of a chemical change e.g. Iron turns to rust
 Kelvin Scale
 The Kelvin is the international unit for temperature. This scale is based on the concept of absolute zero of 0K
 Heat of Fusion
 The amount of heat required to convert a a solid at it’s melting point to a liquid without an increase in temperature
 Heat of Vaporization
 The amount of heat required to convert a liquid at its boiling point into vapor without an increase in temperature.
 Kinetic Molecular Theory
 1. They are composed of individual particles that are in continuous, random, straight-lined motion2. The distance between their particles are so great compared to the value of the individual particles that the value of the individual particles is considered to be negligible (i.e. ideal gas particles d not take up spaces)3. The particles have no attraction forces between them4. collisions between gas particles are completely elastic; in other words, an equal amount of energy is transferred between the particles- there is no net gain or loss of energy and the system remains constant
 Real Gases (like oxygen, nitrogen, etc.)
 Do no behave exactly like an ideal gas because they are real1. particles (atoms/molecules) have attraction for each other2. particles occupy volume
 PLIGHT
 real gases behave like ideal gases under certain conditionsP= pressureL= lowI= ideal G= gasH= highT= temperature
 Pressure
 the force applied to an object per unit area ex: pounds per square inch (lbs/inch^2)
 STP (Standard Temperature and Pressure)
 conditions most often used to study or test a chemical Standard Temperature- 273 KStandard Pressure- 1atm= 760 mmHg= 101.3 kPa
 Vapor Pressure
 The pressure exerted as a liquid changes into a gas (as temperature increase vapor pressure increases)
 Boiling Point
 The temperature at which the vapor pressure of a liquid is equal to the pressure pushing down on the surface of the liquid. The normal boiling point of a liquid is the temperature at which the vapor pressure equals standard pressure. As vapor pressure goes up the boiling point will increase
 Boyle’s Law (pressure acting on volume)
 At constant temperature, as pressure on a gas increases the volume decreases
 Charles’ Law (temperature acting on volume)
 At constant pressure as the temperature of a gas is increased volume increases
 Gay-Lussac’s Law (temperature acting on pressure)
 At constant volume, as the temperature of a gas increases the pressure increases
 Combined Gas Law
 P1V1 = P2V2 (on the reference table) T1 T2
 Avogardo’s Law
 Equal volumes of gases at the same temperature and pressure contain an equal number of gas particles: NUMBER TO REMEMBER 6.02 x 10^23
 Democritus
 All matter is composed of tiny, indivisible particles he called atomes. His idea was dismissed by other Greek Philosophers including Aristotle
 Antoine Lavoisier
 Law of conservation of mass/matter: Matter is neither created nor destroyed
 Joseph Louis Proust
 Law of definite proportions: A given compound always contains the same elements in the same proportions by mass. The ratio is always fixed
 Joseph Dalton
 The properties of matter can be explained in terms of atoms
 Dalton’s Atomic Theory of Matter
 1. Each element is composed of extremely small, indivisible particles called atoms2. All atoms of a given element are identical, but they are different from those of any other element3. Atoms are neither created nor destroyed in any chemical reaction4. A given compound always has the same relative numbers and kinds of atoms
 J.J. Thomson
 Cathode Ray Tube Experiment. passed an electrical curent through a glass tube containing different gases at low pressure with magnetic plates on either side of the tube. Concluded that the cathode ray was made up of negatively charged particles
 Ernest Rutherford
 Gold Foil Experiment. Aimed a beam of alpha particles at an extremely thin piece of gold foil and came to two important conclusions:1. an atom is made up of mostly empty space2. the majority of an atom’s mass and all of it’s positive charge are concentrated in a central core called the nucleus
 Subatomic Particles
 Protons- positive charge, located in the nucleus and has a mass of 1Neutrons- has no charge, located in the nucleus and has a mass fo 1Electron- has a charge of negative one, located outside the nucleus and has a mass of 1/1840
 Atomic number
 The number of protons in the nucleus of an atom. The identity of an atom is determined by it’s atomic number. Ex: every carbon atom has six protons
 Mass number
 The sum of the protons and neutrons in an atom. The number of neutrons can be determined by subtracting the atomic number from the mass number. If you see element-# that is showing the mass number
 Isotope
 Atoms/elements with the same number of protons, but different number of neutronsEx. Carbon-12, Carbon-13, Carbon-14
 Ions
 When an atom gains or loses an electrons and has a net positive or negative charge. They have a charge either positive or negative
 Average Atomic Mass
 This is weighted average of the naturally occurring isotopes for an element. This weighting is a result of their precent abundances on Earth.
 Principle Energy Levels
 Describe the approximate distance from the nucleus. The farther away fromt he nucleus, the more energy associated with that level. – Energy levels are designated with the letter n; n can be the numbers 1-7-1 is closest to the nucleus and has the least amount of energy associated with it
 Sublevels
 Describes the shape of the electron cloud or orbital-sublevels designated s,p,d,f-s has the lowest energy associated with it while f has the highest
 Orbitals
 Each sublevel may contain one or more orbitals (or electron clouds) having different spatial orientations. These are the areas of highest probability of finding electrons
 Ground State
 When the atom (e^-) of an element occupies the lowest energy levels 1st (in order). Elements are in their most stable state when in the ground state
 Excited State
 When the atom absorbs energy and moves of jumps up energy level(s), they are considered to be int eh excited state (not in order). All atoms want to be in the most stable state possible. In order for an atom to be go back to ground state from the excited state the atom must release the energy they had originally absorbed. The energy is released in a form of light that is characteristic to each element.
 Dmitri Mendeleev
 Dmitri Mendeleev arranged elements by increasing atomic mass and similar chemical properties. He found arranged this way had repetitive patterns. At this time, only 70 elements had been discovered. If no known elements seemed to “fit” in a place that went with the patterns. Mendeleev would leave the space blank and elements that had not yet been discovered that fit this pattern were put in these spaces.
 Henry Moseley
 Henry Moseley determined the atomic number for all elements. He proposed the elements in the periodic table should be arranged by increasing atomic numbers which turnet out to be more accurate. This is how the Periodic Table is arranged today
 Periodic Law
 When elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic trend.
 Metals and Non metals
 More than two thirds of all elements are metal. Metals are shiny, malleable, ductile, good conductors of heat and electricity, low ionization energy, lose electrons and form positive ions. Non-Metals are dull, brittle, poor conductors of heat and electricity, have high ionization levels, like to gain electrons and form negative ions.
 Metalloids
 These are the elements surrounding the stair case, between the metals and non-metals. They have both metallic and non-metallic properties. They include: B, Si, Ge, As, Sb and Te. Metals are located to the left and non-metals are located to the right.
 Common group names
 Group 1- Alkali Metals (no including H)Group 2- Alkaline Earth Metals(^These groups from strong basses)Group 17- Halogens form SaltsGroup 18- Noble Gases- Chemically un-reactive inert due to filled valence shells. They exist as monatomic molecules
 BrINClHOF
 These are elements that naturally exist as diatomic molecules. Br2 I2 N2 Cl2 H2 O2 F2
 Atomic radius
 One-half the distance between the nuclei of two identical atoms when they are joined together (i.e. the distance from the nucleus of atoms to the valence shell)
 Ionization Energy
 The energy required to remove an electron from an atom in the gas phase. The energy need to remove the first electron is called the first ionization energy; to remove the second electron is called the second ionization energy, and so on.
 Electronegativity
 An atom’s attraction for electrons when chemically bonded with another atom.
 Group Trends
 1. As you move down a group the atom’s radius increases. This is because an increase in the number of occupied energy levels.2. As you move down a group IE and EN decrease. This ia because the increased distance between the protons in the nucleus and the valence electrons.3. As you move down a group metallic properties increase.
 Period Trends
 1. As you move from left to right within a period, the atomic radius decreases. This is because a greater molecular charge.2. As you move from left to right within a period, the IE and EN both increase. This is because of the decreased distance between the protons and electrons
 Shielding Effect
 When the innermost electrons block the attractive force of the protons on the valence electrons
 Kernel
 the innermost electrons and nucleus
 Octet Rule
 Atoms acquire eight valence electrons by taking or sharing electrons; they want to have an electron configuration like that of the closest noble gas. Most atoms are stabilized with 8 valence electrons. (Exceptions: H, He, Li, Be, B (these only need two)
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