Chemistry Midterm Study Guide 2016
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Mass
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the amount of matter in an object
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Weight
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the gravitational pull on an object
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Scientific method
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the process of studying natural phenomena, involving observations, forming laws and theories, and testing of theories by experimentation
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Scientific method steps
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1. identify the problem 2. form a hypothesis 3. create an experiment 4. perform the experiment 5. analyze the experiment 6. communicate the results
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Qualitative data
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data that is observed and not measured; descriptions
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Quantitative data
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data that is measured; numeric
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Dependent variable
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the variable that is measured in the experiment and affected by the experiment
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Independent variable
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the variable that is changed by the scientists, experiments only have 1 of these
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Mass
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Kilogram (Kg)
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Volume
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Liter (L)
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Length
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meter (m)
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Temperature
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Kelvin (k)
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Electric Current
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Ampere (A)
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Amount of substance
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mole (mol)
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Time
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second (s)
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Temperature Conversions
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C= K-273 K= C+273 C= F-32/1.8 F= (C*1.8) +32
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Density
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mass/volume
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Accuracy
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getting as close to the true value as possible
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Precision
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getting the same answer over and over again
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Random era
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errors are random
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Systematic era
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something wrong with the system you are using, low accuracy and high precision
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Percent error
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Actual-experimental/actual x 100
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Significant figures
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-all digits between 1-9 -zeros between significant figures -trailing zeros if the number has a decimal point -zeros following a decimal sig fig
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Not significant figures
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-zeros in the beginning of a number whose only function is to place the decimal point
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Multiplying/dividing significant figures
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limit and round to the least # of sig figs in any of the factors
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Adding/subtracting significant figures
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limit and round to the least # of decimal places in any of the numbers
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Intensive properties
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-do not depend on the amount of matter present -Includes: boiling point freezing point melting point density flammability combustibility corrosiveness condensation point hardness color
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Extensive properties
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-depend on the amount of matter present -Includes: volume mass length weight
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Physical properties
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-properties that are measurable -Includes: color odor texture density volume states of matter melting point boiling point
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Chemical properties
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-material's properties that become evident during/after a chemical reaction -Includes: burning oxidation tarnishing rust fermentation :sugar to alcohol combustion: burning electrolysis: water to hydrogen and oxygen gas
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Physical change
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-change in state of matter -Includes: melting boiling evaporating sublimation: dry ice melting from solid to gas ductile: drawn into a wire malleable: pounded into sheets
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Chemical change
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-changes into a new substance
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Evidence of chemical change
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1. gas produced 2. heat/light is released or absorbed 3. permanent color change 4. formation of precipitation
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Endothermic
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light/heat is absorbed
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Exothermic
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light/heat is released
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Gas
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no definite shape or volume
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Liquid
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definite volume but no definite shape
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Solid
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definite volume and shape
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Mixture
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-blend of 2 or more substances -can be physically separated -not chemically bonded
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Pure substance
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-elements and compounds -requires a chemical process to separate
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Element
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a substance that cannot be broken down into simpler substances by chemical or physical means
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Compound
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a substance with constant composition that can be broken down into elements by chemical composition
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Homogeneous mixture
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mixture that is uniform throughout; solution
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Heterogeneous mixture
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mixture that is not uniform throughout; can see different parts Examples: milk, fog, jello
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Centrifugation
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-process of separating a mixture based on the densities of the particles in that mixture -physical seperation -Example: blood: more dense on bottom, less dense on top
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Filtration by Gravity
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-process of separating a mixture based on the size of the particles in that mixture -separate an insoluble solid in a liquid -physical separation -Example: strainer
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Decantation
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-pouring off of a liquid from a mixture that contains both a liquid and a solid -separate 2 immiscible liquids -physical separation -Example: oil and vinegar, oil and water
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Simple Distillation
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-separate a soluble solid in a liquid -physical -Example: salt water
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Chromatography
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-separate miscible liquids -2 phases: mobile and stationery -physical separation Example: separating ink from paper
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Evaporation
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-recover a soluble solid from a liquid -physical separation -Example: salt water, sugar water
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Fractional distillation
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-separate 2 or more miscible liquids by their boiling points -physical separation -Example: water and alcohol
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Seperatory Funnel
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-separating 2 immiscible liquids -physical separation -example: oil and vinegar
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Filtration by vacuum
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-collect an insoluble solid from a mixture -physical seperation -Example: sand and water
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Electrolysis
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-separation of hydrogen atoms from the oxygen atoms in a water molecule -chemical separation -Final result: oxygen and hydrogen gas separated
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Law of conservation of mass
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matter cannot be created or destroyed; it can only be converted from 1 form to another; mass of reactants= mass of products
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Law of definite proportion
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-proportion of mass of elements in a compound is always the same -discovered by Proust
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Law of multiple proportion
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-mass of 1 element can combine with fixed masses of another element to make different things -discovered by John Dalton
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Democritus
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-Greek philosopher -among first to suggest existence of atoms
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Dalton
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-used Lavoisier's idea of experimenting -law of multiple proportions -1st atomic theory
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Dalton's 1st atomic theory
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-all matter is made up of atoms -all atoms are indivisible (wrong b/c of subatomic particles-p, n, e) -atoms of different elements are different -atoms of the same elements are the same (wrong b/c of isotopes) -atoms can combine, rearrange, and separate to form new compounds
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Thomson
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-Cathode ray experiment (electrons) -plum pudding model
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Cathode ray experiment
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-discovered electrons -ray negatively charged -ray deflected away from negative, towards positive
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Cathode ray
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stream of electrons produced at the negative electrode of a tube containing a gas at low pressure
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Plum pudding model
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negative embedded in positive
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Ernest Rutherford
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-Gold Foil experiment(nucleus and protons)
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Gold foil experiment
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-alpha particles have positive charge and are the size of Helium atoms -expected all particles to go straight through, some were deflected straight back Found: -nucleus is small, dense and contains protons (positive) -discovery of nucleus and protons
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Nuclear Model
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-positive nucleus with electrons circling -atom is mostly empty space
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Mass number
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# of protons + neutrons
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Neutron
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-neutral charge -located in the nucleus -atomic mass - atomic #
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Proton
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-positive charge -located in the nucleus -atomic #
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Electron
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-negative charge -located outside the nucleus -atomic # in a neutral atom
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atomic mass
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weighted average mass
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atomic mass unit (amu)
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1/12 the mass of a carbon-12 atom
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Ion
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a charged atom
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Cation
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-positive charge -lose electrons
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Anion
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-negative charge -add electrons
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Isotopes
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atom of the same element with different numbers of neutrons, have a different atomic mass
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Electron scanning microscope
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instrument used to generate images of individual atoms
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Radioactivity
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the spontaneous decomposition of a nucleus to form a different nucleus
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Electron Capture
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(on left side)
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Electromagnetic spectrum
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all the different forms of electromagnetic radiation, have different wavelengths and frequencies
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Wavelength
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the distance between 2 crests
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Frequency
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numbers of waves that pass
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Speed of light
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frequency x wavelength
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Energy
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E=hv
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Photoelectric effect
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electrons are emitted from a metal surface when light of a certain frequency shines on it
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Quantum
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minimum amount of energy that can be gained or lost by an atom
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Excited state- ground state
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releases energy in form of light: colors produced
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Bohr quantum model
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electrons in specific orbitals (set path), only worked for hydrogen because it has 1 electron
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Heisenberg uncertainty principle
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you cannot know the velocity and position of an electron at the same time, impossible to assign set paths to an electron
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Electron cloud
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-discovered by DeBroglie, Schrodinger, Heisenberg, and Einstein
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S orbital
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spherical appears in 1-7 can hold 2 electrons
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P orbital
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dumb-bell appears in 2-7 can hold 6 electrons
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D orbital
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2 dumb-bells appears in 3-7 can hold 10 electrons
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F orbital
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shape too complicated appears in 4-7 can hold 14 electrons
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Balmer series
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visible light
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Lyman series
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UV light
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Paschen series
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Infared light
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Aufbau principle
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electrons must occupy the lowest energy level lst
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Hund's rule
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electrons want to be alone before they pair up
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Pauli exclusion principle
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2 electrons can occupy each platform, must have different spins
