Chemistry Midterm

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indicators of physical changes

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- change in visible appearance, not composition
- reversible or irreversible
- ex: boil, melt, cut, bend, split, crack

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indicators of chemical changes

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- energy is absorbed or released (temperature changes)
- color changes
- gas production (bubbling, fizzing, odor change)
- forms precipitate (solid that separates from solution and will not dissolve)
- irreversibility (not easily reversible)

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heterogeneous mixtures

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- not uniform in composition
- two or more phases

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homogeneous mixtures

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- same composition throughout
- single phase

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extensive properties

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- depend on amount of matter in sample
- mass, volume, calories

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intensive properties

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- do not depend on amount of matter but type of matter
- hardness, density, BP

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physical changes

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- changes in physical properties of a substance
- change in visible appearance without changing composition

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chemical changes

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change where new form of matter is formed

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physical properties

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- observed without changing composition of the substance
- measured or observed with senses
- color, odor, hardness, density, MP, BP, state, solubility, cutting, grinding

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chemical properties

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- ability for substance to undergo chemical change
- after change, new substance is formed

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separation of mixtures

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- some can be separated easily by physical means
- differences in physical properties can be used to separate mixtures
- filtration – separates solid from liquid in a heterogeneous mixture (by size)
- components of dyes such as ink may be separated by paper chromatography
- distillation – takes advantage of different boiling points

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states of matter

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solid, liquid, gas, plasma

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solid

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- matter that cannot flow
- definite shape and volume
- fixed, closely packed arrangement of particles
- particles cannot move from their spot, can move slightly back and forth (vibrate)

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liquid

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- flows
- particles are free to move
- definite volume, no definite shape but can conform to container
- particles are packed closely together, but can move away from their spots (possibly packed closer than in a solid)

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gas

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- no definite shape or volume
- particles spread apart, filling all the space available
- particles can move around freely (more freely than liquid)
- compressibility – either spread apart or squeezed together
- have most energy in their particles

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plasma

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- formed at high temperatures
- ionized phase of matter
- very good conductor of electricity
- affected by magnetic fields
- indefinite shape, indefinite volume

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quantitative

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- uses numbers to describe
- preferred by scientists because it is easier to check

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qualitative

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- does not describe with numbers
- very descriptive
- sometimes subjective

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scientific method

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logical way of solving problems or answering questions

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SI base units

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- length – meter (m)
- mass – grams (g)
- time – second (s)
- temperature – Kelvin/Celsius (K/Cº)
- energy – Joules (J)
- volume – liters (L)
- amount of substance – mole (mol)

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SI prefixes

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SI derived units

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- combination of SI units
- either multiply or divide units

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rules for significant figures and rounding

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- all numbers other than zero
- which zeros count

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adding sig figs

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subtracting sig figs

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multiplying sig figs

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dividing sig figs

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metric conversions (i.e. grams –> kilograms)

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dimensional analysis (i.e. converting ft to cm)

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- mathematical technique that allows you to convert from one unit to another

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density

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the ratio of mass to volume, or mass divided by volume

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accuracy

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refers to the closeness of measurements to the correct or accepted value of the quantity measured

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precision

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refers to the closeness of a set of measurements if the same quantity made in the same way

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molar mass

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the mass of one mol of a pure substance

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mass

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amount of matter in an object

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weight

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gravitational pull on an object

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structure of the atom

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composed of two main regions: nucleus and electron cloud

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Dalton's atomic theory and changes made to it

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scientific discoveries of Thomson

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identified electrons using cathode rays

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scientific discoveries of Rutherford

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- positively charged nucleus
- classified radiation

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scientific discoveries of Dalton

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- atomic theory

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scientific discoveries of Millikan

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electron's charge

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scientific discoveries of Bohr

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model of the hydrogen atom

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scientific discoveries of DeBroglie

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wave particle duality of nature

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atomic number

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number of protons in the nucleus of each atom in a given element

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mass number

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protons + neutrons

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isotopes

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two or more atoms having the same atomic number (same number of protons) but different mass numbers (due to different number of neutrons)

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two different types of notation for writing isotopes

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- nuclear notation (ex: 235/92 Uranium)
- hyphen notation (ex: Uranium-235)

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law of multiple proportions

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two or more elements can combine to form different compounds in whole number ratios

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law of definite proportions

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no matter how of any compound you have, its always the same proportions of elements

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law of conservation of mass

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states that mass is neither created nor destroyed during ordinary chemical reactions or physical changes

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subatomic particles

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- protons – positive particles in the nucleus
- neutrons – neutral particles in the nucleus
- electrons – negative particles in the electron cloud

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nuclear forces

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short range p+ and nº, p+ - p+ and nº - nº forces that hold nuclear particles together

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Avogadro's number

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- number of particles in one mole of a pure substance
- 1 mole = 6.022 x 10^23

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Mole conversions (mol –> g, mol –> molecules, etc)

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wavelength

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distance between corresponding points on adjacent angles

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frequency

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number of waves that pass a given point in a specific time (usually one second)

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electromagnetic spectrum

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all forms of electromagnetic radiation

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quanta

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orbital

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three-dimensional region around the nucleus that indicates the probable location of an electron

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orbit

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quantum numbers

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they specify the properties of atomic orbitals and the properties of electrons in orbitals

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quantum energy – step ladder from notes (order of sublevels and orbitals)

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Heisenberg uncertainty principle

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it is impossible to determine the position and velocity of an electron or any other particle (at the same time)

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how atom reaches excited state, how it returns to ground state

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- it reaches excited state from having a higher potential energy than its ground state
- it returns to ground state when it gives off the energy it gained
- the energy it gives off is in the form of electromagnetic radiation

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list of all the sublevels in an atom, how many electrons can be in each sublevel

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(see p. 105)

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be able to write all three types of electron configuration – orbital, electron, noble gas

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Aufbau principle

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an electron occupies the lowest energy orbital that can receive it (wants to be very stable)

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Hund's rule

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orbitals of equal energy are each occupied by one electron before any orbital is occupied by a 2nd spin state

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Pauli exclusion principle

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no two electrons in the same atom can have the same set of four quantum numbers (each orbital can have a max of 2 electrons of opposite spin)

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period trends – atomic radii

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period trends – ionic radii

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period trends – ionization energy

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period trend – electronegativity

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arrangement of modern periodic table

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in order of increasing atomic number so that elements with similar properties fall in the same column or group

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Moseley

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his work led to both the modern definition of the atomic number and the recognition that the atomic number is the basis for organization of the periodic table

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Mendeleev

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created the first periodic table

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horizontal rows

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- called periods

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vertical columns

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- called groups

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location, valence electrons, stability of metals and nonmetals

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- valence electrons are located in the outermost s and p sublevels
- metals are less stable than nonmetals

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valence electrons

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an electron that is available to be lost, gained, or shared in the formation of chemical compounds

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properties of each group

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lanthanides

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actinides

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group names

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assigned elements

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chemical bond

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mutual attraction between nuclei and valence electrons of two atoms that binds them together

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intermolecular forces

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- forces of attraction between molecules
- vary in strength but are usually weaker than bonds

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ionic bonding

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- when electrons are taken by one atom from another atom

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covalent bonding

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- when electrons are shared between two atoms

Front 90

types of compounds formed using each bond

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7 diatomic molecules

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BrINClHOFs:
- Bromine
- Iodine
- Nitrogen
- Chlorine
- Hydrogen
- Oxygen
- Fluorine

Front 92

how polarity is determined

Back 92

- by polarity of the bonds and shape of the molecule

Front 93

resonance

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refers to bonding in molecules that cannot be correctly represented by a single Lewis structure

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polar covalent bonds

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- covalent bond in which electrons are shared unequally
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nonpolar covalent bonds

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- a covalent bond in which electrons are shared equally
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drawing Lewis structures

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