Chemistry 105 Exam 1

chemistry

the study of matter by studying behavior of atoms and molecules

atoms

submicroscopic particles; building blocks of ordinary matter

molecules

groups of 2 or more atoms in geometric shape; at least 2 atoms in a definite arrangement held together by chemical force (not all molecules are compounds)- H2=molecule; CO=molecule and compound

classifications of matter

state or composition

state- solid

atoms super close together; definite shape and volume; amorphous (atoms do not have long range pattern of arrangement) or crystalline (atoms have long term pattern of arrangement); condensed

state- liquid

atoms close but can move freely; definite volume, not shape (fluid); condensed

state- gas

atoms far apart; no definite shape or volume; atoms move freely; compressible

composition- pure substance

non variable compound; made up of only one compound (can't separate=element or can separate=compound)

element

can't be broken down

compound

2 or more substances (elements) in fixed ratio; pure substance; different properties than component elements

composition- mixture

variable compound; two or more components in proportion that can vary

homogeneous

uniform (tea and sugar)

heterogeneous

non-uniform (wet sand)

physical means

used to separate mixture into pure components

chemical means

used to separate compound into pure components

physical change

no alteration of composition or identity (ice melting, sugar dissolving, etc.)

chemical change

alters composition or identity of substance (hydrogen gas burns in oxygen to make H2O, rust, etc.)

physical property

color, odor, boiling point, density

chemical property

acidity, toxicity, flammability

extensive property

depends on amount of matter (mass, volume, length)

intensive property

independent of amount (density, temperature, color)

phase change

does not change composition; solid to liquid to gas

energy

capacity to do work

work

directed energy

kinetic energy

energy produced by moving object Total E= ke+pe

potential energy

energy available due to position Total E= ke+pe

thermal energy

energy associated with random motion of atoms and molecules (type of kinetic energy)

Law of Conservation of Energy

total quantity of energy in the universe is constant; all energy can be converted to other forms, but never created or destroyed

mass

measure of quantity of matter; does not change with gravity

weight

force that gravity exerts on object

volume

1cm^3=1mL

density

mass/volume- kg/m^3, g/L, g/mL

1g/cm^3=1g/mL=1000kg/m^3

K, F, C (temperature)

K=C+273.15

F=1.8(C)+32

C=(F-32)/1.8

precision

measurements close to each other

accuracy

measurement close to actual value

Law of Conservation of Mass

in a chemical reaction, matter is neither created nor destroyed; mass of reactants=mass of products

Law of Definite Properties

all samples of a particular compound will have the same proportions of constituent elements ex: H2O-2:1

Law of Multiple Proportions

when 2 elements (A and B) from 2 different compounds, the masses of B that combine with 1 g of A can be expressed as a ratio of small whole numbers ex. NO- 14:16, NO2- 14:32, N2O- 28:16

Dalton's Atomic Theory

explains above laws; beginning of modern chemistry

1. elements are composed of tiny, indestructible parts called atoms

2. all atoms of a given element are identical

3. atoms combine in simple whole number ratios to form compounds

4. atoms of one element can't change into atoms of another element (chemical reaction is separation, combination, or rearrangement rather than creation or destruction)

cathode ray

Thompson's experiment; beam of particles in cathode ray tube travel from negative charged end (cathode) to positive charged end (anode); cathode ray has negative electrical charge; discovered electron (smaller than atom); discovered charge to mass ratio of electron

oil drop

Millikan's experiment; oil drops acquired electrons (negative charge) as they fell; lower plate had electrical strength to halt the fall of the drops; charge to be -1.6x10^.19 C and found mass of electrons to be 9.1x10^-28 g

Thompson's plum pudding model

electrons stuck in positively charged background (blueberries and muffin)

Rutherford's gold foil experiment

positively charged alpha particles pass through gold foil, but some deflect off at different angles- charges not spread out evenly across atom; positive charges held in dense core (nucleus); disproved plum pudding model

Chadwick

discovered neutrons

atomic number

number of protons in nucleus of each atom of an element (fixed number); determines identity; neutral atom: atomic number=# of neutrons

mass number

# of protons + # of neutrons

isotopes

atoms which have the same atomic number, but different atomic masses

atomic mass

mass of he atom in atomic mass unit; atomic mass unit= 1/12 of the mass of a Carbon12 atom

atomic mass=sum(abundance of isotope n)x(mass of isotope n)

ions

atom or group of atoms with a + (cation) or - (anion) charge; charge= loss or gain of electrons

monatomic ions

ions which consist of only one atom: Na^+, Cl^-, Mg^2+, O^2-

polyatomic ions

ions which consist of more than one atom: OH^-, SO4^2-, NH4^+, CO3^2-

ionic compound

compound formed from 2 or more ions: LiCl, MgF2 (metal and nonmetal; cation and anion)

Periodic Law

when arranged in order of increasing atomic mass, certain sets of properties recur periodically

Mendeleev's periodic table

periods: horizontal rows

families or groups: vertical columns (elements have similar properties)

used periodic law to predict properties or undiscovered elements

regions

metals, metalloids, nonmetals

metals

solid at room temperature; reflective surface; conduct heat and electricity; malleable and ductile; lose electrons and form cations in reactions; 75% of elements; lower left of table

non-metals

found as solids, liquids, and gases; poor conductors of electricity and heat; solids are brittle; gain electrons and form anions in reactions; upper right of table

metalloids

some properties of metals and some of non-metals; semi-conductors

Important group- H

non-metal; colorless, diatomic gas, low melting point and density; reacts with nonmetals to form molecular compounds- HCl and H2O; H reacts with metals to form hydrides- metal hydrides react with H2O to form H2; H+(halogen) dissolves in water to form acids

Important group- Alkali metals

1A; soft, low melting point and density; flame tests: Li=red, Na=yellow, K=violet; very reactive, never find uncombined in nature; tend to form water soluble compounds; colorless solutions; react with water to form basic (alkaline) solutions and H2 (releases lots of heat)

2Na+2H2O-->2NaOH+H2

Important group- Alkali earth metals

2A; harder, higher melting point and density; flame tests: Ca=red, Sr=red, Ba=green; reactive (less than above); form stable, insoluble oxides form which they are extracted; oxides=basic=alkaline earth metal; reactivity with water to form H2: Be=none, Mg=steam, Ca,Sr,Ba=cold water

Halogens

7A; nonmetals and diatomic; F2 and Cl2-gases, Br2-liquid, I2-solid; very reactive; react with metals to form ionic compounds; H(halogen)=acid;

HF(weak acid)

Noble gases

8A; very unreactive (hard to become gain or lose electrons); gas at room temperature; low melting and boiling point

mole (mol)

# of atoms in exactly 12.000g of C12- 6.022x10^23

molar mass

mass of one mole of units of a substance in grams (atomic mass)

elements and compounds

elements can combine to make limitless compounds; properties of compounds different than those of its component elements

chemical bonds

forces that hold atoms together in a compound

ionic bond

transfer of electrons form metals to nonmetals results in cations and anions held together by electrostatic force

covalent bond (molecular bond)

sharing of electrons (-) between two nonmetal nuclei (+); results in a molecule

chemical formula

give elements in compound with relative number of each element as a subscript: H2O, AlPO4, C4H8

molecular formula

C2H6 (actual)

empirical formula

CH3 (lowest number whole ratio)

atomic elements

elements whose particles are single atoms

molecular elements

elements whose particles are multi-atom molecules

molecular compounds

compounds whose particles are molecules of only nonmetals

ionic compounds

compounds whose particles are cations and anions

diatomic elements

H2, N2, O2, Cl2, Br2, I2

diatomic molecules

CI2, HF, NO

polyatomic molecules

CO2, HCN, CH3OH