Chem Midterm

four rules for counting sig figs

all non-zero digits are significant

zeros between non zeros are always significant

a zero at the beginning of a number is never significant

zeros at the end of a number are significant if the number contains a decimal point

Rule for adding and subtracting sig figs

# of decimal places in the result equals the number of decimal places in the least precise measurement.

rules for dividing and multiplying sig figs

your final answer will have only as many sig figs as the number with the fewest sig figs

equation for density

D=m/v

unit for density

g/cm3 or kg/m3

physical property

a characteristic that is not associated with a chemical composition

physical intensive property

properties that do not depend on the amount of matter present

physical extensive property

depends on the amount of matter present

chemical property

the ability to change from one type of matter to another

Example of Physical Intensive Property

denisty

examples of chemical properties

reactivity and flammability

examples of physical extensive property

mass, volume, length, weight, size

four observations that indicate a chemical change

change in color, transfer of energy, production of gas or light, formation of a precipitate

physical change

A change in a substance that does not involve a change in the identity of the substance

chemical change (chemical reaction)

a substance is transformed into a chemically different substance

example of chemical change

rusting

Examples of physical change

melting, freezing, vaporization, condensation, sublimation

mass

the amount of matter in an object

volume

The amount of space an object takes up

quantitative

Data that is in numbers

Qualitative

Data in the form of words

accuracy

how close a measurement is to the true value

Precision

a measure of how close a series of measurements are to one another

si

International System of Units

water displacement

a method used to determine the volume of an irregular solid

Element

A substance that cannot be broken down into simpler substances

Compound

a substance that is composed of two or more separate elements

a mixture.

examples of compounds

water and carbon dioxide

pure substance

cannot be separated by physical means

Mixture

A combination of two or more substances that are not chemically combined

homogeneous mixture

a mixture in which the composition is uniform throughout

examples of homogeneous mixture

Salt water Kool-Aid

heterogeneous mixture

A mixture that is not uniform in composition

components are not evenly distributed throughout the mixture

examples of heterogeneous mixture

Salt & Pepper

Water & Sand

exothermic reaction

A reaction that releases energy in the form of heat

endothermic reaction

A reaction in which energy is absorbed

kinetic energy

energy of motion

melting

solid to liquid

Freezing

liquid to solid

Evaporation

Liquid to gas

Condensation

Gas to liquid

system

a limited and well defined part of the universe

surroundings

everything outside the system

heat capacity

the amount of heat needed to raise the temperature of a substance by one degree.

specific heat

The amount of heat required to raise the temperature of 1 gram of a substance by 1 degree celcius

specific heat capacity equation

c = q/mΔT

specific heat equation

q = mcΔT

first law of thermodynamics

Energy cannot be created or destroyed, the amount of heat produced or consumed must be equal to the amount of heat absorbed or lost

equation for heat within a system

qsystem=-qsurrondings

density of water

1 g/mL

specific heat capacity of water

4.184 J/gC

Order of Evolution of Atomic Model

Aristotle, Dalton, Thomson, Rutherford, Bohr, Chadwick

Aristotle idea of atom

made of fire, water, air, earth

Dalton atomic theory

proposed atomic theory based on experimentation, observation, evidence.

Dalton Model of Atom

Neutrally charged sphere, completely filled

atomic theory

(1) All matter is composed of atoms

(2) Atoms of a given element are identical

(3) Atoms of different elements are different

(4) Atoms combined separate and rearrange in chemical reactions

Atoms combine in simple whole number ratios

Thomson Atomic Theory

discovered the electron via ray experiment, oil drop experiment, double split experiment

Thomson model of the atom

Plum pudding model

Rutherford atomic theory

discovered the atomic nucleus and its concentrated positive charge conducted the goil foil experiment

Rutherford atomic model

Nucleus in the center with a positive charge with floating electrons around

Bohr atomic theory

Electrons orbit the nucleus

Bohr Model

electrons in circular orbits around the positive nucleus

Chadwick atomic theory

discovered neutrons

atomic number

number of protons

mass number

the sum of the number of neutrons and protons in an atomic nucleus

Nuclide symbol

mass number on top, atomic number on bottom

Nuclide name

name- atomic mass

Ion

loses or gains electron, creates charge

Isotopes

Atoms of the same element with different numbers of neutrons, changes mass

Cation

positively charged ion- gives away electron, positivity charged (metals)

Anion

A negatively charged ion-gains electron, negatively charged (non metals)

Change to -ide

gained electrons, non metals.

average atomic mass

the weighted average of the masses of all naturally occurring isotopes of an element

abundance of isotopes

Percentage of each isotope weight

calculating atomic mass

multiply each atomic mass by the percent abundance add them up Divide by 100 or move two decimal spaces in percent

atomic orbital

a region of space in which there is a high probability of finding an electron

s orbital

spherical, have 1 orientation, and can hold max of 2 electrons

p orbitals

are dumbbell shaped, have 3 orientations, and can hold max of 6 electrons

d orbitals

5 orientations, can hold max of 10 electrons

f orbital

7 orientations and can hold max of 14 electrons

Electron configuration

the way in which electrons are arranged in various orbitals around the nuclei of atoms.

Coefficient

principal quantum # (n)

Energy level

Indicates shell's proximity to

nucleus

Letter

sublevels: s, p, d, & f orbitals

subshell shapes depend on orbital momentum

Superscript

Number of electrons in sublevel

Total # of superscripts = atomic #

Aufbau Principle

electrons fill lower-energy atomic orbitals before filling higher-energy ones

Hund's Rule

Every orbital in a sublevel is singly occupied before any orbital is doubly occupied

Pauli Exclusion Principle

Electrons in the same orbital have opposite spin

Metals Properties

Good conductors of heat and electricity, Luster (shiny), Malleable, Ductile

Solids (except Hg), Lose electrons to form cations

Metalloids properties

Properties of both metals and nonmetals.

Semiconductors

Found on staircase.

nonmetals properties

Insulators- poor conductors of heat and electricity, Brittle, Dull All three states of matter, Gain electrons to form anions

periods

rows on the periodic table

Groups

Vertical columns on the periodic table

Alkali Metals

Group 1, Very reactive metals, Soft metals

Alkaline earth Metals

Group 2, Reactive metals (due to 2 valence electron) Soft metals, Ductile, Malleable

Transition Metals

groups 3-12 Higher melting points

Lower reactivity

Halogens

17 or 7a, very reactive nonmetals

Noble Gases

Nonreactive (INERT) nonmetals

Inner Transition Elements

Known as lanthanide & actinide

Used in nuclear reactions