Final Exam Flashcards
Chemistry
The study of the properties and behavior of matter
Matter
The physical material of the universe; anything that has mass and occupies space
Property
Any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types
Element
A substance that cannot be decomposed into simpler substances. Each is composed of a unique kind (one type) of atom
Atoms
Small building blocks of matter
What are properties of matter related to?
The composition (kinds of atoms the matter contains) and the structure (arrangement of the atoms)
Molecules
Two or more atoms joined in specific shapes
States of matter
Solid, liquid, gas
Pure substance (substance)
Matter that has distinct properties and a composition that does not vary from sample to sample. All substances are either elements or compounds. Has a fixed composition
Ex: water and sodium chloride
Compounds
Substances composed of two or more elements; contain two or more kinds of atoms
Mixture
Combinations of two or more substances in which each substance retains its chemical identity
Law of Constant Composition/Law of Definite Proportions
The elemental composition of a compound is always the same. Compounds composed in the lab and the corresponding compound found in nature are the same. A pure compound has the same composition and properties under the same conditions
Mixtures (conceptual stuff)
Most of the matter we encounter consists of mixtures of different substances. Each substance in a mixture retains it scheme identity and properties. The composition of a mixture can vary (unlike substances). The substances making up a mixture are called components of the mixture. Some mixtures do not have the same composition, properties, and appearance throughout. Ex: rocks, hard wood, coffee with sugar
Heterogeneous mixture
Vary in texture and appearance in any typical sample
Homogeneous mixture/solutions
Mixtures that are uniform throughout. Solutions can be solids, liquids, or gases. Ex: air
Physical properties
Can be observed without changing the identity and composition of the substance. Ex: color, odor, density, melting point, boiling point, hardness
Chemical properties
Describe the way a substance may change/react to form other substances. Ex: flammability
Intensive properties
Do not depend on the amount of sample being examined and can be used to identify substances. Ex: temperature, melting point
Extensive properties
Depend on the amount of sample and relate to the AMOUNT of substance present. Ex: mass and volume
Physical change
A substance changes its physical appearance but not its composition (it is the same substance before and after the change.) All changes of state (changes in temperature and pressure)
Chemical change/chemical reaction
A substance is transformed into a chemically different substance. Ex: hydrogen burning in air because it combines with oxygen to form water, digesting food, mixing acid and base
Distillation
Separates the components of a a homogeneous mixture. The process depends on the different abilities of substances to form gases. Ex: boiling a solution of salt and water: water will evaporate and the salt is left behind
Chromatography
Technique used to separate mixtures based on the differing abilities of substances to adhere to the surfaces to the surfaces of solids
Energy
The capacity to do work or transfer heat. Does not have a mass but its effects can be observed and measure
Work
Energy transferred when a force exerted on an object causes a displacement of that object. w = F*d
F= force exerted on the object
d= distance
Heat
The energy used to cause the temperature of an object to increase
Force
Any push or pull exerted on the object. Ex: gravity and the attraction between opposite poles of a bar magnet
Kinetic energy
Energy of motion. Increases as an objects velocity or speed increases. The transfer of heat is the transfer of kinetic energy at the molecular level
Potential energy
Stored energy that arises from the attractions and repulsions an object experiences in relation to tore objects
Chemical energy
Released when bonds between atoms are formed, and consumed when bonds between atoms are broken
Quantitative
Associated with numbers
SI units
Particular choice of metric units for use in scientific measurements. Has 7 base unites from which all other units are derived
Length
Meter m
Mass
Kilogram kg
Temperature
Kelvin K
Time
Secondly s or sec
Amount of substance
Mole mol
Electric current
Ampere A or amp
Luminous intensity
Candela cd
Law of Conservation Mass
In a chemical reaction, there is no change in the total mass of the materials reacting as compared with the materials that are formed
Scientific method
Collect information, formulate a hypothesis, test the hypothesis, formulate a theory, repeatedly test theory
Peta
P 10^15
Tera
T 10^12
Giga
G 10^9
Mega
M 10^6
Kilo
k 10^3
Deci
d 10^-1
Centi
c 10^-2
Milli
m 10^-3
Micro
u 10^-6
Nano
n 10^-9
Pico
p 10^-12
Femto
f 10^-15
Atto
a 10^-18
Zepto
z 10^-21
Mass
A measure of the amount of material in an object. SI base unit of mass is the kg, about 2.2 lbs
Temperature
A measure of the hotness or coldness of an object. A physical property that determines the direction of heat flow
Heat flow
Always follows from a substance at a higher temperature to one of lower temperature
Absolute zero
Zero on the Kelvin scale. The temp at which all thermal motion ceases. -273.15 C
Derived unit
Obtained by multiplying or dividing of one or more of the baseunits
Volume
Derived SI unit is m^3
Density
The amount of mass in a unit volume of a substance
density=mass/volume
Calorie
1 cal = 4.184J
1 Cal = 1000 cal = 1 kcal
Inexact numbers
Those whose values have some uncertainty. Numbers obtained by measurement
Precision
A measure of how closely individual measurements agree with one another
Accuracy
Refers to how closely individual measurements agree with the correct or true value
Standard deviation
Reflects how much the individual measurements differ from the average
Significant figure rules
Zeros between nonzero digits are always significant.
Zeros at the beginning are never significant.
Trailing zeros are significant if the number contains a decimal point
Dimensional analysis
Units are multiplied together or divided into each other along with the numerical values. Equivalent units cancel each other
Given unit * desired unit/given unit = desired unit
Conversion factor
Fraction whose numerator and denominator are the same quantity expressed in different units
Law of constant composition
In a given compound, the relative numbers and kinds of atoms are constant
Law of conservation mass
The total mass of materials present after a chemical reaction is the same as the total mass present before the reaction. Atoms are neither created no destroyed during a chemical reaction, the changes that occur during any reaction merely rearrange the atoms
Law of multiple proportions
If two elements A and B combine to form more than one compound, the masses of B that can combine with a given mass of A are in the ratio of small whole numbers. Ex: ratio of masses of oxygen per gram of hydrogen in water
is 2:1
Radioactivity
The spontaneous emission of radiation
Cathode rays
Radiation produced between the electrodes when a high voltage was applied to the electrodes in the tube. Originated at the negative electrode and traveled to the positive electrode. Although rays cannot be seen, their presence was detected because they fluoresce (give off light)
Thomson’s cathode ray experiment
The electron is a negatively charged particle so the electric field deflected the rays in one direction, and the magnetic field deflected them in the opposite direction. Thomson adjusted the strength of the fields so that the effects balanced each other, allowing the electrons to travel in a straight path to the fluorescent screen
Rutherford’s experiment with 3 types of radiation
3 types of radiation: alpha, beta, and gamma (y). Showed that the paths of alpha and beta radiation are bent by an electric field, in opposite directions. Beta rays bend upwards towards the positively charge place. Gamma rays are unaffected by the plates and go in a straight line. Alpha rays bend downward towards the negative charge plate.
What makes an atom of one element different from an atom of another element?
The atoms of each element have a characteristic number of protons
Atomic number
The number of protons in an atomy of any particular number. Hydrogen has an atomic number of 1. Also the number of electrons
Mass number/atomic weight
Number of protons plus neutrons in the atom. Carbon has an atomic weight of 12.0107amu
Isotopes
Atoms with identical atomic numbers but different mass numbers (different number of neutrons)
Atomic weight
The average atomic mass of an element. It is found by summing over the masses of its isotopes multiplied by their relative abundances
Periodic table
The arrangement of elements in order of increasing atomic number, with elements having similar properties place in vertical columns
Groups
Vertical columns. Elements in a group often exhibit similarities in physical and chemical properties because they have the same arrangement of electrons at the periphery of their atoms
Metallic elements/Metals
All elements on the left and middle except for hydrogen
Nonmetallic elements/metals
Separated from the metals by a stepped line that runs through B, Is, As, Te, At.
Metalloids
Elements that lie along the stepped line that has properties that far between those of metals and nonmetals
Molecular form
Two or more of the same type of atom bounded together
Chemical formula
Ex: O2
Molecular compounds
Compounds composed of molecules contain more than one type of atom. Ex: a molecule of the compound CH4. Most molecular compounds are nonmetals
Molecular formula
Chemical formulas that indicate the actual numbers of atoms in a molecule Ex: C2H2
Empirical formula
Chemical formulas the give only the relative number of atoms of each type in molecule. The subscripts in an empirical formula are always the smallest possible whole-number ratios
Ex: Molecular formula of ethylene is C2H4 and the empirical formula s CH2
Structural formula
Depicts atoms represented by their chemical symbols and lines to represent bonds
Perspective drawings
Use wedges and dashed lines to depict bonds that are not in the plane of the paper. Give a crude sense of the 3D shape of a molecule
Ball and stick models
Show atoms as spheres and bonds as sticks. Accurately represents the angles at which the atoms are attached to one another in a molecule
Space filling models
Depict what a molecule would look like if the atoms were scaled up in size. Show the relative size of the atoms. Useful for picturing how two molecules might fit together or pack in the solid state. Doesn’t show angles between atoms as well as ball and stick models
Ions
Metal atoms tend to lose electrons to formations and nonmetal atoms tend to gain electrons to form anions
Ionic compounds
Tend to be composed of a metal cation and nonmetal anion. Ex: NaCl
Polyatomic ions
Consists of atoms joined as a molecule but carrying a net positive or negative charge. Ex: NH41+ and SO42-
Chemical equations
Represent chemical reactions
Combination reactions
Two or more substances react to form one product. A combination reaction between a metaled a nonmetal produces an ionic solid
A+B–>C
Decomposition reaction
A single reactant breaks apart to form two or more substances
Many metal carbonates decompose to metal oxides and carbon dioxide when heated
Ex: BaCO3 –> BaO(s) + CO2(g)
C–>A+B
Combustion Reaction
Rapid reactions that produce a flame. The combustion of.a hydrocarbon produces CO2 and H2O
H2O gas or liquid depends the reaction conditions
Formula Weight
The sum of the atomic weights of the atoms in the chemical formula of the substances in atomic mass units.
If it is an ionic substance, sum the atomic weights of the atoms in the empirical formula
Molecular Weight
The formula weight if the chemical formula is that of a molecule
Percentage composition/Elemental composition
The percentage by mass contributed by each element in the substance. If the chemical formula is know use the equation on pg 92
Mole/Avogadro’s number (N_A)
SI Unit for the amount of a substance. The amount of matter that contains the number of atoms in exactly 12 g of isotopically pure 12C which is 6.0221415 x 10^23
Molar mass
The atomic weight of an element in atomic mass units is numerically equal to the mass in grams of 1 mol of that element
Ex: Cl has atomic weight of 35.5 amu. 1 mol of Cl has a mass of 35.5 g
The molar mass in grams per mole of any substance is numerically equal to its formula weight in amu
Limiting reactant
The reactant that is completely consumed in a reaction. It determines (limits) the amount of the product formed. Once all of the limiting reactant is consumed, the reaction stops
Excess reactants
Reactant that is not used up
Theoretical yield
The quantity of product calculated to form when all of a limiting reactant is consumed
Actual yield
The amount of product actually obtained. Is almost always less than the theoretical yield and can never be greater than it