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 measure
meter –> length
Kelvin –> temperature
moles –> number of particles
Liter –> volume
Amperes –> electric current
pascal –> pressure
joule –> heat
gram –> 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 figures
2. Round your answer to the least number of significant figures
example: 2.35×3.845×8.9=80.418175 cm^3
only 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 places
2. Round your answer to the least number of decimal places
example: 2.35+3.845+8.9= 15.095
the smallest decimal place is the tenths so the answer would be 15.0
Dimensional Analysis
A technique used to convert(or change) units
1. Determine the unit equality
2. Write down the given quantity
3. Determine the proper conversion factor
4. Set-up and solve
example: 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 motion
l l
l oo l
l oo l
Liquids
Particles are in free motion, very close together and take the shape of the container
l l
loool
loool
Gases
Particles have free random motion and are usually far apart
l o o l
lo o ol
l 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 motion
2. 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 them
4. 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 real
1. particles (atoms/molecules) have attraction for each other
2. particles occupy volume
PLIGHT
real gases behave like ideal gases under certain conditions
P= pressure
L= low
I= ideal
G= gas
H= high
T= 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 K
Standard 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 atoms
2. All atoms of a given element are identical, but they are different from those of any other element
3. Atoms are neither created nor destroyed in any chemical reaction
4. 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 space
2. 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 1
Neutrons- has no charge, located in the nucleus and has a mass fo 1
Electron- 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 neutrons
Ex. 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 Salts
Group 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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