Science Midterm Flashcards
Pure chemistry
The pursuit of chemical knowledge for its own sake
Applied chemistry
Research that is directed toward a practical goal or application
Extensive properties
Properties that depend on the amount of matter in the object. Ex: volume, mass
Intensive properties
Properties that depend on the TYPE of matter in a sample. Ex: color, melting point
Solids
Expand slightly when heated
Liquid
Tends to expand slightly when heated
Gas
Expands when heated
Gas (definition)
A substance that exists in a gaseous state in room temp
Vapor (definition)
The gaseous state of a substance that is generally solid or liquid at room temp
Plasma
State of matter found at extremely high temp
Physical properties
Properties of a substance that can be observed without changing the substance’s composition
Physical change
A change that alters the appearance or state of matter but NOT its composition. Some changes are reversible, some are not.
Chemical change
Will always change the composition of the matter.
Possible clues of a chemical change
Change of color, production of gas, transfer of energy
Chemical property
The ability of a substance to undergo a specific chemical change
When can chemical properties be observed
When chemical change happens
Precipitate
The stuff that comes from clouds
Heterogenous mixture
Has individual parts known as phases
Homogenous mixture
Has only one phase
Distillation
Separation of components of a mixture based on differences in boiling point
Elements
Pure substances that cannot be broken into a more simple form
Compounds
Two or more different elements chemically compound in a definite ratio by mass
True or false: compounds can be broken into simpler substances by chemical means
True
Are properties of a compound different or similar to the properties of elements it is composed of?
Different
Substance
Composition is fixed in the material
Mixture
Composition in the material may vary
Chemical symbols
Are used to represent elements
Chemical formulas
Used to represent compounds. Involve a combination of chemical symbols and numbers called subscripts
What do subscripts indicate in a chemical formula?
The amount of atoms of an element present
Chemical reaction
Involves the making/breaking of chemical bonds. Turns one or more substances into one or more new substances.
Chemical equations
Shorthand way of representing the events of a chemical reaction
Reactant
Beginning substance, written to the left of the arrow
Product
End substances, written to the right of the arrow
Accuracy
How close a measurement comes to actual value
Precision
How close a series of measurements are to one another
Significant figures
Applies only to measured values
Electric current unit
Ampere
Unit for amount of substance
Mole (mol)
Energy
The capacity to do work or produce heat
Unit of energy
Joule
Calorie
The amount of heat that raises the temp of 1 gram pure water by 1 degree celsius
Conversion factors
Ratios whose value is equal to one based on scientific quantities and measurements
Density
Ratio of the mass of an object to its volume
Is density an intensive or extensive property
Intensive (but depends on the type of matter)
Important exception for the rule: volume decreases as temperature increases
Water, its volume increases as its temp decreases (over a certain range of temp)
Atom
Smallest part of an element that retains its identity in a chemical reaction
Democritus
Believed atoms were indivisible and indestructible. His ideas did not explain chemical behavior however.
John dalton
Proposed the atomic theory. Had the idea of solid indivisible atoms. Explained chemical reactions but fell short of what was true.
Atomic theory
- atoms of the same element are identical and vice versa
JJ Thomson
Made the Cathode Ray Tube which helped him discover the electron. Used the plum pudding model (ball of positive charge with electrons stuck)
Robert Millikan
Calculated the mass of an electron to be 1/1840 that of a hydrogen atom
Eugen Goldstein
Discovered protons
James Chadwick
Confirmed the existence of the neutron
Ernest Rutherford
Proposed electrons surround nucleus all the positive charge and ALMOST all the mass concentrated in the nucleus, which is composed of protons and neutrons.
Atomic Number
Number of protons in the nucleus of an atom; distinguishes elements from each other
Mass number
The sum of the protons and neutrons in the nucleus of an atom
Isotopes
Atoms of the same element that differ in the number of neutrons
Comparison of isotopes
The mass of each isotope differs.
The chemical activity of each isotope is identical.
Atomic mass
Weighted average mass of all isotopic forms of an element.
What does the value of atomic mass show?
It reflects both the mass and the relative abundance of the isotopes as they occur in nature
Atomic mass units (amu)
It is 1/12th the mass of a carbon-12 atom
Atomic mass of an element equals:
(mass of each isotope) times (the natural abundance, expressed as a decimal). Then add the products.
Bohr
Electrons found in orbits around nucleus. However, no info about sublevels within orbits
Quantum mechanical model
Predicts the probability of finding an electron within a region but cannot show its exact location or describe its motion. Can also predict shapes of various orbitals
Quantum
Energy required to move from one energy level to the next highest
Ground state
An electron that has not acquired any energy to move up to the next highest energy level
Excited state
An electron that has acquired enough energy to move up to the next highest energy level
The 4 Quantum Numbers
Principal quantum number (n)
azimuthal quantum number (lowercase L)
magnetic quantum number (m)
spin quantum number
Principal quantum number
Tells us about the energy level the electron is found in
Azimuthal quantum number
Gives info about sublevels in an atom
Magnetic quantum number
Gives info about the orbitals within a sublevel
Spin quantum numbers
Gives info about the direction of spin of an electron within an orbital. Max number of electrons within orbital is two.
Atomic Orbital
Region in atom where there is a high probability of finding an electron
J.W Dobereiner
Designed a classification system that grouped elements into groups of three elements with similar properties
Dmetri Mendeleev
Arranged elements in the periodic table inti groups based on a set of repeating properties. Gaps in the table corresponded to elements not yet discovered
Problems with Mendeleev’s table
Arranging elements according to their atomic mass caused problems
Henry Moseley
Determined the atomic number for each known element
Periodic law
When elements are arranged according to increasing atomic number, which brings a periodic repetition of their physical and chemical properties
Classifying metals
Are good conductors of heat and electricity, are malleable, ductile, and lustrous. All are solid at room temp except mercury.
Classifying nonmetals
Tend to be poor conductors of heat and electricity, are mostly gases at room temp. As solids they tend to be brittle.
Classifying metalloids
Have properties of both metals and nonmetals.
Is Aluminum a metal or nonmetal or metalloid
Metal
Atomic radii
One half the distance between the nuclei of two atoms of the same element when atoms are joined
Trends in atomic radii (left to right)
Left to right decrease because the increasing nuclear charge pulls the electrons in the highest occupied energy level closer to the nucleus
Trends in atomic radii (top to bottom)
Top to bottom increases because number of energy levels increase
Ions
an atom/group of electrons that has a + or - charge
Ionization energy
The energy required to remove an electron from an atom
First ionization energy
Energy required to remove the first electron from an atom
Second ionization energy
The energy required to remove the second electron from an ion with a charge of 1+
Trends in ionization energy (left to right)
left to right increase because atomic radii decrease so electrons are closer to nucleus and harder to remove
Trends in ionization energy (top to bottom)
top to bottom decrease because atomic radii increase so electrons are farther away from nucleus and harder to remove
Electronegativity
the ability of an atom of an element to attract electrons when the atom is in a compound. Depends on the electron affinity of an atom
Electron affinity
A measure of an atom’s ability to gain electrons
Trends in electronegativity (left to right)
Left to right increases because atomic radii decreases so there is a greater attraction by the nucleus for electrons
Trends in electronegativity (top to bottom)
Top to bottom decreases because atomic radii increases so there is lesser attraction by nucleus for electrons
Valence electrons
responsible for determining the chemical properties of an element
Electron dot/Lewis dot diagram
shows valence electrons as dots. Only done for atoms of representative elements.
Gilbert Lewis
Created the Octet Rule
The Octet Rule
Used to explain why atoms form certain kinds of ions and molecules.
Ionic compound
cations and anions, if an ion loses an electron, something has to gain it at the same time
Ionic bonds
transfer of electrons between atoms
formula unit
smallest representative unit of an ionic compound
Properties of Ionic compounds
most are crystalline solid at room temp, tend to have high melting points, ions are arranged in repeating three dimensional patterns, can conduct an electric current if melted or dissolved in water but not when dry
Stock system
ex: Iron (II) ion, Iron (III) ion
Electron mobility
characteristic of metals being ductile and malleable
Alloy
a mixture composed of a metal and another element
Metallic bonds
cations closely packed and a sea of electrons surrounding it
Alloys vs constituents
Alloys are better because they have corrosion resistance and extra strength
Polyatomic ions
they are tightly bound groups of atoms that behave as a unit and carry a change
Ternary Ionic Compounds
contains atoms of three or more different elements, usually one or more polyatomic ions
Molecular compounds/covalent compounds
between non metals only, happens when electrons are shared
